MakerMask https://makermask.org Science-based mask information Thu, 15 Oct 2020 19:58:06 +0000 en-US hourly 1 https://wordpress.org/?v=5.5.1 https://makermask.org/wp-content/uploads/2020/06/cropped-erin_surge_mmlabeled-32x32.png MakerMask https://makermask.org 32 32 175102756 Fluid Resistance: Mask Material Test Results https://makermask.org/mask-material-test-results-fluid-resistance/?utm_source=rss&utm_medium=rss&utm_campaign=mask-material-test-results-fluid-resistance https://makermask.org/mask-material-test-results-fluid-resistance/#comments Tue, 13 Oct 2020 22:47:21 +0000 https://makermask.org/?p=1629 New test results show that upcycled spunbond nonwoven polypropylene (NWPP) mask materials can provide high-level (ASTM Level 2) fluid resistance. MakerMask has supported the use of spunbond nonwoven polypropylene (NWPP) in homemade masks due to NWPP’s inherent hydrophobicity, or water resistance. Thanks to community contributions, we were able to put reclaimed NWPP to the test […]

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New test results show that upcycled spunbond nonwoven polypropylene (NWPP) mask materials can provide high-level (ASTM Level 2) fluid resistance. MakerMask has supported the use of spunbond nonwoven polypropylene (NWPP) in homemade masks due to NWPP’s inherent hydrophobicity, or water resistance. Thanks to community contributions, we were able to put reclaimed NWPP to the test (ASTM F1862).

Fluid resistance is a key feature of medical masks. It is important for masks to act as a barrier to liquids to help prevent bodily fluids (e.g., respiratory droplets, spit, and blood) from passing through the mask. This is particularly relevant for masks designed to contain respiratory droplets, such as those used for source control in response to the COVID-19 pandemic.

An image of the MakerMask: Origami showing water beading up on the surface of the spunbond nonwoven polypropylene (NWPP) mask material
Hydrophobic spunbond nonwoven polypropylene (NWPP) used in the MakerMask: Origami.

Test Method (ASTM F1862)

After pre-screening several material combinations for water resistance, we sent samples of 3-layer NWPP (n=40) for formal fluid resistance testing (ASTM F1862) by the Groupe CTT Group. ASTM F1862 is the required fluid resistance test for medical masks. This test is important because it evaluates whether the provided material samples can act as barriers to fluids (i.e., prevent fluid from soaking through, or penetrating, from the outside of the material to inside ).

To do this, the outside of each mask material is sprayed with a jet of synthetic blood at one (or more) pressure level (80 mm Hg, 120 mm Hg, and 160 mm Hg). Material samples are considered fluid resistant (ASTM F1862 / F1862M – 17; Midha et al, 2012) if they successfully act as a barrier to the synthetic blood at one of the three pressure levels. They are further classified on a scale of 1 to 3 based on the highest fluid pressure they block successfully: ASTM Level 1 (80 mm Hg), ASTM Level 2 (120 mm Hg), and ASTM Level 3 (160 mm Hg).

Fluid Resistance Results

We hypothesized that our material combination would pass the fluid resistance test at ASTM Level 1. However, it performed better than expected and passed at ASTM Level 2. The results are summarized in the table below (Note: 39 samples were tested, and results are reported for the highest passing level).

ASTM Level Fluid Pressure Tested Sample count Passing Sample count Testing results
1 80 mm Hg
2 120 mm Hg 32 31 PASS
3 160 mm Hg 7 4 FAIL

Click here for the Full Report: “GCTTG Group Report on MakerMask 3-Layer Mask Material Samples”.

Deeper Dive: Maker Mask ASTM F1862 Test Samples & Conditions

Test Samples

  • Number of Samples Shipped for Testing: 40
  • Composition of Sample: 100 gsm spunbond nonwoven polypropylene (NWPP), sourced from reusable bags
  • Sample Construction: 3 layers, sewn together around the edges with polyester thread
  • Size of Each Sample: 16 cm x 16 cm square
  • Pre-Treatment of Samples: All samples were boiled and then air dried prior to testing

Test Procedure

  • Horizontal projection of fixed volume synthetic blood at a known velocity.
  • Conditioning atmosphere: 21±5ºC, 85±5% R.H.
  • Testing atmosphere (< 1 minute):  19.5ºC, 74% R.H.
  • Distance of the mask from the canula: 30.5 cm
  • Volume of the fluid impacting the mask: 2.0 ml
  • Number of Samples Tested: 39

 

Photo of spundbond nonwoven polypropylene (NWPP) material that passed ASTM F1862 fluid resistance testing. (left) Green NWPP showing splatter of syntethic blood on the outside surface. (right) the inside surface of the same fabric sample showing that it successfully prevented the blood from penetrating to the inside of the mask.
A material sample that has passed the ASTM F1862 test with synthetic blood at 120 mm Hg. The outside surface (left) shows the splatter of synthetic blood from the test while the inside surface (right) of the same sample shows that none of the synthetic blood penetrated through the material.

Conclusion

These results show that a three-layer spunbond NWPP material combination can act as a barrier to fluids such as respiratory fluids and droplets. Although results will vary depending on specific materials used, these findings support a potential advantage of 3-layer NWPP masks over masks consisting exclusively of hydrophilic (absorbent) materials such as cotton or those constructed from a single layer of NWPP.

NOTE: In keeping with FDA guidance, MakerMask designs are intended for use as source control and are not intended for surgical use or use in other high-risk activities. Information provided is for reference only and is only applicable for the specific materials tested; results may vary. For more information about FDA regulatory requirements for masks check out the updated August 2020 EUA for Surgical Masks and the MakerMask blog post about Mask Labeling Requirements.

Thank You!

Special thanks to Hope Metzler who put together all the test samples discussed in this post.

Thank you to everyone that has donated time and money to help support the scientific investigation and formal testing of mask designs and materials.

(Canva Inforgraphic) Text: Support Lab Testing (Tax-Deductable). With four photos showing the deconstruction of NWPP bags and the creation of the test samples that were sent to the lab for fluid resistance testing
Professional lab testing costs between $500-$1500 depending on the specific test. If you’re in a position to contribute to this work, tax-deductible donations can be made at athenaresponse.org/support . Just choose MakerMask in the project list. THANK YOU!
REFERENCES

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5 Key Considerations For Window Masks https://makermask.org/key-considerations-for-window-masks/?utm_source=rss&utm_medium=rss&utm_campaign=key-considerations-for-window-masks https://makermask.org/key-considerations-for-window-masks/#comments Sat, 08 Aug 2020 01:19:53 +0000 https://makermask.org/?p=1276 One of the challenges with face masks is that they often cover key facial features and expressions that are important for communicating speech and emotions. For many people, this means missing out on smiles, and having a little bit more trouble understanding other people in noisy environments. For people that are deaf, hard of hearing, […]

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One of the challenges with face masks is that they often cover key facial features and expressions that are important for communicating speech and emotions. For many people, this means missing out on smiles, and having a little bit more trouble understanding other people in noisy environments. For people that are deaf, hard of hearing, or learning a language, the elimination of these facial cues poses even larger challenges. In response to some of these challenges during the COVID-19 pandemic, the CDC has suggested that clear face coverings, or window masks, may be appropriate

In this post we’ll discuss three key considerations for the design of window masks — breathability, window material selection, and window attachment strategies — as well as 2 important considerations for their care and use — cleaning and disinfection and fogging. For one sewing pattern consistent with the advice below, see our MakerMask:Expression page.

Note: “Masks” that are completely open at the sides, along the top, or under the chin function more like face shields than like masks, and won’t be discussed in this post.

CDC Statement About Clear Face Coverings in Schools

“Consider use of clear face coverings that cover the nose and wrap securely around the face by some teachers and staff. Clear face coverings should be determined not to cause any breathing difficulties or overheating for the wearer. Teachers and staff who may consider using clear face coverings include:

  • Those who interact with students or staff who are deaf or hard of hearing, per the Individuals with Disabilities Education Act
  • Teachers of young students learning to read
  • Teachers of students in English as a second language classes
  • Teachers of students with disabilities

Clear face coverings are not face shields. CDC does not recommend use of face shields for normal everyday activities or as a substitute for cloth face coverings because of a lack of evidence of their effectiveness for source control.

#1 Breathability

Rule of Thumb: Window size should be no more than 1/3 of the breathable mask area. 

Breathability is an important consideration for all face masks that cover the mouth and nose, and is especially important for window masks, since the clear plastics used as window materials are typically not breathable. In general, as the size of the window within the mask is increased, the breathability of the mask decreases, which increases issues with fogging, makes the mask feel hotter, and can pose problems for users with reduced lung function or those wearing them for prolonged periods of time. 

As a general rule of thumb, no more than 1/3 of the breathable surface area of the finished mask should be constructed from the non-breathable window material. The exact ratio of breathable fabric to window size will depend on the mask design and the breathability of the fabrics used. It is important to note that portions of the mask material that are directly contacting the skin do NOT count as breathable surface area of the mask. So for well-fitted masks, the material in direct contact with the user’s face (e.g., the chin, the cheeks, and the top of the nose) doesn’t count as breathable surface area.

Diagram of breathable area of masks, excluding area that touches the face. For window masks, the window should be no more than 1/3 of this area.
Figure 1: Breathable surface area of masks and ‘rule of thumb’ for window size
Deeper Dive: Breathable Surface Area
For those looking for more than a rule of thumb, instead of looking at the size of the window, look at the breathable surface area of the masks. Consider using the breathable surface area that is typical for N95s as a reference. For N95s, although the surface area of fabric filter material is usually around 150cm2, the breathable surface area is around 100 cm2 (e.g., a 10 cm square or a circle with a diameter of 11.3 cm).

Most cloth masks have relatively large surface areas of 300 – 500 cm2 (e.g., the MakerMask: Surge has a surface area of ~380 cm2), but most of that surface area is touching the face…. This large skin-contacting surface area improves the seal around the face and allows masks to “fit” a broader range of face shapes and sizes. However, these skin-contacting mask surfaces don’t contribute to the breathable area of the mask, and the effective breathable area is restricted to the much smaller area of material immediately in front of the mouth and nose (exactly where the windows in window masks are placed).

Masks that incorporate three dimensional shapes (cup-, cone-, or bag-shaped) that hold the fabric away from the mouth and nose typically have larger breathable surface areas, and are better suited for adaptation with windows. In addition to breathable surface area, the breathability of the mask fabrics should be taken into consideration. In general, aim for at least 100 cm2 of breathable surface area. If the breathability of the combination of fabrics used in the mask is more breathable than an N95, a smaller breathable surface areas might be acceptable. If the the combination of mask fabrics is less breathable than an N95, consider other options. If breathable materials are used, increasing the breathable surface area can help compensate for decreased breathability.

Window material should not touch the mouth or nose. Since current clear plastics used as window materials are not breathable, it is important that they do not block a user’s airways. As such, mask designs which have extra volume around the mouth and nose to ensure sufficient access to breathable mask areas are crucial for window masks.

Pleats improve mask breathability and comfort. If large windows are used, look for modifications to the design that increase the breathable surface area, such as the addition of extra pleats. The reason many air filters and masks include pleats is to increase breathable surface area without decreasing the effective filtration. Consider designs with extra pleats around the clear windows. These will be more breathable.

#2 Window Materials

Rule of Thumb: If you wouldn’t eat off of it, don’t use it as a mask window. 

Consider Food Safe Plastics. Ideally, mask window materials would be made from clear medical-grade materials approved for use in face masks. However, in situations where medical-grade materials are not available, consider food-grade (i.e., food contact safe) window materials. Although we are not planning on eating from our masks, the window materials in masks will be in warm, humid environments in close proximity to the mouth. Food-safe clear plastic materials are commonly available, subject to regulatory controls, and undergo safety testing for contact with things that humans put in their mouths. The plastics most commonly considered food-contact safe are polypropylene (PP), high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polyethylene terephthalate (PET or PETE). If windows are going to be permanently affixed to the mask, consider materials that are labeled “microwave safe” and “reusable” as they are more likely to be compatible with cleaning and disinfection methods. In general, look for materials that are clear, flexible, shatter resistant, and non-toxic. Avoid materials that off-gas, or smell funny, and materials that are brittle.

Safe Usage Symbols for Plastics for Window Masks
Figure 2. Safe Usage Symbols for Plastics for Window Masks (Image source: Nuskinkids)

Top Material Choices: The form and thickness of the specific window materials (typically plastics) used will vary depending on the specific mask design, the way the window will be attached to the mask, and the desired/required cleaning and disinfection methods. Check out the table below for a Deeper Dive into the suitability of clear plastics for window masks.

Category Rating Details
Usually Food-Safe Best Polypropylene (PP): commonly available in food safe containers such as sous vide bags (2 – 3 mil thickness) and other heat-safe clear reusable bags. Thin, flexible PP is easy to heat-seal to spunbond nonwoven polypropylene materials and is the preferred material for heat-sealed masks.
● Look for “microwave-safe” or “boil safe”
● Generally considered reusable
● Usually compatible with hot water washing (melting point: ~160 C)
● Recycling #5
Good High Density Polyethylene (HDPE): flexible and commonly available in food safe sous vide bags and freezer bags. Do NOT steam!
● Moderate Temperature Uses (melting point: ~120C)
● May be considered reusable
● Recycling #2
Good Polyethylene Terephthalate (PET): commonly available around the globe in plastic soda bottles (~17 mil thickness). Rigid and holds shape well for no-sew options (7 mil to 17 mil). Avoid heat.
● Semi-Rigid, Low Temperature Uses, commonly recyclable
● Generally considered single-use
● Recycling #1
Less Good Low Density Polyethylene (LDPE): commonly available in clear plastic wrap and sandwich bags. Lower melting points (~105C) makes it unsuitable for boiling or other high-heat disinfection strategies. Avoid heat.
● Thin, flexible and not very durable, and rarely recyclable. Not Ideal.
● Generally considered single-use
● Recycling #4
Not Usually Food Safe Caution Vinyl (V)*: Vinyl (polyvinyl chloride), is commonly used in shower curtains, but is not usually considered food safe. Check regulations on suitability for food contact. Caution recommended. Avoid heat. Do NOT laser cut.
● Avoid use in masks; Consider other options if available.
● Recycling #3

*See Appendix 1 for more information

Although HDPE and LDPE are considered separately for recycling, in common applications such as freezer bags, the ingredient list says “polyethylene” and doesn’t distinguish between the two types.

#3 Window Attachment Method

Rule of Thumb: Avoid holes in the center area of the mask and gaps between the window and mask fabrics

Attaching the window to the mask is where most fabrication challenges arise. You want to minimize leaks around the window, which means minimizing gaps, holes, and seams. Carefully inspect the area around the window of the masks for holes and/or gaps after construction and before each use. 

Window attachments methods can be divided into three general categories: sealed-in windows, sewn-in windows, and removable windows.

Sealed-in Windows

Sealed-in windows (e.g., the MakerMask: Expression) use heat sealed seams to securely bond the window material to the mask fabric. This method requires careful selection of compatible window materials and mask fabrics (e.g., synthetic materials like polypropylene, polyethylene etc) and a vacuum seal or other tool for making the seals (e.g., an ultrasonic welder). Heat sealing is our preferred technique because it is designed to provide an air-tight seal between the window and the mask body, which helps prevent leaks.

  • Preferred window material: food grade polypropylene; thickness ~3 mil works well
  • Secondary window material: heavyweight polypropylene sheet protectors, preferably acid-free archival grade, >3 mil
  • Preferred mask fabric: spunbond NWPP (not suitable for natural fibers like cotton
  • Advantage: can provide an air-tight seal between the window and the mask body, which helps prevent leaks
  • Disadvantage: Requires careful selection of compatible materials. Likely less durable than sewn-in window options; care should be taken while washing; see section on cleaning and disinfection below.
No sew window mask with heat sealed seams to attach the window to the mask
Figure 3. No sew window mask with heat sealed seams between mask and window area. Can be constructed with either a vacuum sealer or an impulse sealer. Stay tuned for details and patterns!! Email us or leave a comment if you’d like to help beta test the pattern for the “MakerMask: Expression (Beta)“, with optional light for the “MakerMask: Expression Glow” or “Glowmask” for short!

Sewn-in Windows

Sewn-in windows (e.g., the Happy Turtle Mask) are compatible with a wide range of materials, and are the most commonly available window mask patterns. When using sewn-in window masks, holes are a primary concern. Be sure to inspect the area around the window to ensure that stitch lines are covered to minimize the risk of germs getting an express ride from one side of the mask to the other through the needle holes.  

  • Preferred window material: Food-safe flexible plastics (PP, PE), thick enough to support sewing
  • Preferred mask fabrics: Compatible with most mask fabrics (e.g., cotton or NWPP)
  • Advantage: quick and easy to make using tools and strategies familiar from other mask making efforts
  • Disadvantage: Usually introduces needle holes into the window material; verify that water and/or light do not pass through seams around the window material.
Photo Collage of people wearing window masks with sewn in windows courtesy of Hope Metzler
Figure 4. Photo collage of people wearing masks with sewn in windows.

Removable Windows

Removable windows (e.g., “MakeIt Clearly Heard Mask) allow the window materials to be disposed of/cleaned/disinfected separately from the mask body. These designs require more attention to detail in both use and construction. For designs where the windows slip in between mask layers, sealing may require gaskets or large overlapping areas to reduce leakage. Rigid, or semi-rigid window materials are preferred for these types of designs. 

  • Preferred window material: food safe PET such as that used in soda bottles and face shields (>7 mil thickness required; 17 mil works); generally considered disposable
  • Preferred mask fabric: Compatible with most mask fabrics (e.g., cotton or NWPP); fabric mask body may be reused
  • Advantage: window materials can be easily replaced when dirty or damaged, while the mask body is reusable
  • Disadvantage: Challenging to get good seals between window and fabric. Make sure there are no gaps between window and mask
Photo of the "Make It Heard Clearly Mask", a window mask with a Removable Window
Figure 5. A promising technique modification from MakeIt Labs to enhance the sturdiness of the connection between fabric materials is the addition of “cloth rivets”, by punching holes in the plastic around the periphery of the window material and pushing ‘buttons’ of uncut material through it to both hold the window in place AND increase the breathability of the mask by decreasing the surface area of the window material. “MakeIt Clearly Heard Mask”.

Regardless of which attachment method is used, it is important to think about where the window material is mounted onto the mask (i.e., is it mounted to the outermost layer? the innermost layer?) If possible, consider having the window mounted to the outermost layer so that anything that hits the plastic from the outside drips off of the mask instead of into it. 

#4 Cleaning and Disinfection

Rule of Thumb: If you’re not sure if it can be safely reused, consider it disposable.

For window masks that are intended for reuse it is important to pay close attention to the instructions for cleaning and/or disinfection. This is especially true for masks with permanently attached windows since the best strategies for disinfecting the mask fabrics are frequently different from those for washing the window materials. 

  • When buying a window mask, pay attention to the washing and disinfection instructions that come with your mask.
  • If you are making window masks, always include instructions for how to clean both the fabric and the window material. You should also include the type of plastic that the window is constructed from.  

Consider cleaning methods that involve minimal agitation of the window material such as gently hand washing it, or washing on delicate in a lingerie bag. Before each use, carefully observe window materials and areas where windows and masks are joined to ensure that gaps and/or holes have not developed.

Finally, it is important that although most polypropylene window materials as well as some microwave-safe polyethylene materials may be compatible with heat-based disinfection methods, most other clear window materials are not. For example, PET may warp and smell funny when exposed to high temperatures, and vinyl can release toxic byproducts when heated. For more information about cleaning and disinfection, see “Fabric Face Masks: Cleaning and Disinfection.”

Photo of window masks after "home autoclaving"; left a window made from polyethylene (PE), which is shrunken and warped and (right) a polypropylene with no observable change
Figure 6. Example window masks after “home autoclaving” (Instapot). The window made with polyethylene (PE) is shrunken and warped; the window made from polypropylene (PP) is still clear and intact.

#5 Window Fogging

One of the challenges with window masks is that the windows fog easily and accumulate moisture. For mask makers and designers, increasing the breathable surface area of the mask fabric may help reduce fogging, and using anti-fog window materials can also help.

For mask users, anti-fog window coatings may be an option. These coatings are usually surfactants, which help prevent water from beading up on the surface of the window by decreasing the surface tension of the window.

The most common work-around for dealing with window fogging is to add a drop of surfactant (e.g., lotion-free dish soap or baby shampoo) and spread it evenly across the face-side surface of the window material to reduce fogging (to improve the optical clarity, after the detergent dries, buff it with a soft cloth). This approach is effective at reducing fogging, but may leave you with a bitter taste in your mouth … a bit like getting your mouth washed out with soap 😉

  • Allergy consideration: If using soap as an anti-fog agent, make sure that all soap residue is rinsed out of mask materials between uses as soap residue is a common cause of dermatitis. Use fragrance free, hypoallergenic options wherever possible, and consider other surfactants if available.
  • Water resistant materials. For water-resistant mask materials (e.g., NWPP), the soap residue that prevents water from beading up on the surface of the window may also prevent water from beading up on the surface of the NWPP. Take care to limit your application area and rinse well between uses.
Window Mask Fogging Up
Figure 7. Example of a Window Mask Fogging Up (Image Source: Sewing Seeds Of Love)

Final Thoughts

As interest in window masks continues to grow, more patterns are emerging. We are working with groups like OSMS, WeHaveMasks, MakeIt Labs, Helpful Engineering, and other organizations to develop improved window mask designs and will update this page as those become available.Do you have a favorite window mask design? What is the material you are using for the window? How are you keeping them from fogging up? Join the discussion on our Facebook page at www.facebook.com/themakermask.

 

Photo of Dr. Songer in the MakerMask: Expression Glow Prototype: a window mask made with heat sealed seams and an internal light to improve visibility of the mouth in dimly lit situations.
Stay tuned for details and patterns for the No Sew “MakerMask: Expression” with heat sealed seams; we’re calling the version with the optional light the “MakerMask: Expression Glow” or “Glowmask” for short!! Email us or leave a comment if you’d like to help beta test the pattern for the “MakerMask: Expression (Beta)” and the “Glowmask”)…

Appendix 1

Vinyl (PVC)
If considering vinyl materials, careful evaluation of manufacturing standards and controls are critical, since vinyl chloride poses potential inhalation as well as ingestion risks (PVC deeper dive, WHO 1984, WHO 2004, Cancer.gov, California Prop 65: “Avoid plastics known as polyvinyl chloride (PVC) or vinyl (with recycle code 3).”). 
PEVA
PEVA, or polyethylene vinyl acetate, is rarely considered food-safe (check with manufacturer), but is generally considered safer than PVC and is not listed by California Prop 65 as a material to avoid at this time. 

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Myths about Masks https://makermask.org/myths-about-masks/?utm_source=rss&utm_medium=rss&utm_campaign=myths-about-masks Tue, 04 Aug 2020 16:25:33 +0000 https://makermask.org/?p=1259 In this guest post, our collaborators from the ROSE Project (Reusable Open Source Equipment) debunk some common myths about face masks for COVID-19 and share the facts about masks.

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In this guest post, our collaborators from the ROSE Project (Reusable Open Source Equipment) share the facts about face masks for COVID-19 and dispel common mask myths.

You may be asking yourself, do we even need face masks? Are they safe to wear? Let’s tackle some of the common myths about face masks that have popped up during the COVID-19 pandemic.

Infographic - 2 Boxes. (box 1) Myth: "Wearing a face mask increases the inhalation of CO2 and decreases your intake of oxygen, causing hypercapnia which weakens the immune system. (box 2) FACT, Face masks are made to be breathable.

  • Oxygen passes freely through masks because oxygen particles are incredibly tiny (0.0005 microns). You will not be deprived of oxygen by wearing a mask. Masks just force the air to flow through a filter to catch viruses, bacteria and pollutants. The extra force required may mean that some people will have to work a bit harder to breathe.
  • Medical-grade face masks are designed and tested to make sure that air actually passes through the masks. When you breath out, the CO2 in your breath will pass through the mask because CO2 is also incredibly tiny (0.00065 microns). Medical-grade masks are carefully tested to be both effective and safe for human use.
  • Your immune system will still protect you while you wear a mask. The immune system is complicated and has many ways to regulate itself and make sure it’s working properly. It takes a LOT to completely shut down your immune system. Having to breathe more heavily for a short period of time is not enough to shut down your body’s ability to fight infections.

 

Myth: Face masks increase the risk of COVID-19 infection

Fact: Wearing a mask may reduce your risk of COVID-19 infection, when worn correctly and combined with proper hand hygiene.

  • The job of a face mask is to catch and trap viruses on the outside surface. The virus gets stuck in the mask and can’t go through the mask when you breathe.
  • Droplets from someone with the virus who is speaking, coughing or sneezing close to you can land on your mask. If you touch these droplets on the surface of your mask and then touch any other part of your face, like your eyes, you can infect yourself with COVID-19.

Infographic (2 blocks). Block 1: "Myth: There's no evidence that masks work to filter COVID-19 or that wearing a mask helps prevent the spread." Block 2: "Fact: Masks give you an added layer of prevention, keeping everyone's germs to themselves"

 

 

  • Proper hand hygiene and physical distancing are the best ways to prevent the spread of COVID-19.
  • There have been many studies during influenza pandemics and the SARS epidemic in the past 10 years, looking at the effectiveness of face masks. The research shows that wearing a mask can reduce the spread of viruses, as long as you are washing your hands before putting them on and washing your hands after taking them off.
  • If you are using a reusable face mask, it needs to be washed after every use.

Simply put, face masks allow air to flow through the mask, trapping virus particles on the outside and preventing the spread of COVID-19. Proper hand hygiene before and after mask wearing is important, so make sure you wash your hands with soap for 20 seconds every time. Stay safe and healthy and please share these facts with your family and friends!

About the Author: The ROSE project team (Reusable Open Source Equipment), based out of Toronto, is developing a reusable mask design that meets medical standards. This will result in less waste and a more stable supply chain for masks. To learn more about the ROSE project, visit the website.

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Mask Fabrics: Introduction to Fibers and Fabrics https://makermask.org/mask-fabrics-101-introduction-to-fibers-and-fabrics/?utm_source=rss&utm_medium=rss&utm_campaign=mask-fabrics-101-introduction-to-fibers-and-fabrics https://makermask.org/mask-fabrics-101-introduction-to-fibers-and-fabrics/#comments Wed, 29 Jul 2020 15:49:12 +0000 https://makermask.org/?p=1198 How Do I Choose Fabrics for Masks for COVID-19? Since March, it seems like there has been a constant barrage of conflicting information about which fabrics are the best for masks for COVID-19. We’ve put together this crash course on mask fabrics to provide some of the fundamental concepts in fabrics and how they are relevant for our collective mask making efforts.

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How Do I Choose Fabrics for Masks for COVID-19?

Since March, it seems like there has been a constant barrage of conflicting information about which fabrics are the best for masks for COVID-19. We’ve put together this crash course on mask fabrics to provide some of the fundamental concepts in fabrics and how they are relevant for our collective mask making efforts.

  • In Mask Fabrics 101, we’ll focus on fiber origin and structure and the importance of these features in preliminary evaluation of fabrics for masks.
  • In Mask Fabrics 201 (also included in this post) we’ll do a deeper dive into fiber properties that influence the safety and performance of mask materials and discuss some of the different nonwoven fabrics used in masks (e.g., spunbond, meltblown, and nanofiber materials).

Mask Fabrics 101

Fibers are the basic building blocks of fabrics and textiles. Fibers are defined as flexible strands of material that are much longer than they are wide. The fiber composition, or fiber content, of fabrics affects their properties and their suitability for use in masks. These fibers are then constructed into fabrics. The ways fabrics are constructed (woven, knit, or nonwoven) effect their filtration characteristics and suitability for use in fabric masks.  

Fiber Origin & Content

Although fibers can be characterized in many different ways, one of the most common ways fibers are distinguished is based on their origin, i.e., whether the fibers are  natural or manufactured (synthetic). The specific type of material that fibers are constructed from is referred to as the fiber content (e.g., cotton or polypropylene). For mask makers it is considered best practices to include information about fiber content with masks. For manufacturers, this best practice may be a legal requirement (see regulatory agencies for guidance).

Inforgraphic: Categories of Textile Fibers Divided into Manufacture Fibers and Natural Fibers
Figure 1. Textile fibers are frequently discussed as either manufactured fibers or natural fibers. Image Source: http://gpktt.weebly.com/

Table of Natural vs. Manufactured Fibers
Natural Fibers Manufactured Fibers
Plant Fibers – harvested from cellulose- containing parts of plants including the seed (e.g., cotton), the bast (e.g., linen), and the leaf. Synthetic Fibers – created from synthetic polymers and chemicals (e.g., nylon, polyester, polypropylene, polyethylene, polyurethane, and carbon fibers).
Animal Fibers – derived from animal proteins such as the hair-sheared from sheep (e.g., wool) and silk from the cocoons of silkworms. Regenerated Fibers – typically cellulose-based, re-created from naturally occurring materials (e.g., wood, bamboo, and seaweed) including rayon, acetate, and modal.
Mineral Fibers – derived from minerals (e.g., Asbestos). Inorganic Fibers – manufactured from glass (e.g., fiberglass and microglass), metals (e.g., silver and copper), and other non-carbon based sources.

Natural Fibers

Natural fibers are strands of long, thin, flexible material that are created in nature by plants, animals, or geological processes (i.e., mineral fibers). 

Although natural fibers are rarely used in commercial medical masks, they are commonly used in fabric masks to contain droplets to help reduce the spread of COVID-19. According to the WHO, absorbent hydrophilic materials (e.g., cotton) should be used for the innermost mask layers (i.e., those contacting the face).

Fiber Source Properties Disadvantages For Masks Advantages For Masks
Cotton Cotton – Seed ●      Absorbent
●      Not electrostatic
●      May Shrink
●      Slow to Dry
●      Inexpensive
●      Easily sourced
●      Easy to wash
●      Can Iron at 204C (400F)
Linen Flax – Stem (bast) ●      Absorbent
●      Not electrostatic
●      Expensive
●      Wrinkles
●      Less filtration (Larger fiber diameters)
●      Dries Quickly
●      Feels Cool
●      Can Iron at 230C (445F)
Silk Silkworm- Cocoon ●      Absorbent
●      Electrostatic when dry
●      Expensive
●      Less durable
●      Soft/Fine
●      Lightweight
●      Can Iron at 148C (300F)

 

Manufactured Fibers

Manufactured fibers are strands of long, thin, flexible materials that have been significantly altered (in terms of chemical composition, structure, and properties) by industrial processes. These fibers include synthetic fibers (e.g., polyester, polypropylene, and carbon fiber), regenerated fibers (e.g., rayon, viscose, and bamboo), and inorganic fibers (e.g., fiberglass, silver, and copper fibers).

Medical masks are typically made from layered combinations of fabrics made from manufactured fibers (e.g., polypropylene).  For fabric masks, the most commonly used manufactured fibers are non-absorbent, or hydrophobic, synthetic fibers. According to the WHO, fabrics made from synthetic hydrophobic fibers (e.g., polypropylene or polyester) should be used for outermost mask layers.

Fiber Properties Disadvantages for Masks Advantages for Masks
Polypropylene (PP) ●      Hydrophobic
●      Electrostatic
●      Lower melting point
●      Less UV-resistant
●      Not Dyeable
●      Ironing is not recommended; if required, use lowest setting (135C; 275F)
●      Dries Quickly
●      Light weight
●      Most Hydrophobic
●      Most Electrostatic
Polyester (PET) ●      Hydrophobic
●      Electrostatic
·
●      Less hydrophobic
●      Can be stained
●      Dries quickly
●      Can be Ironed on low to medium
(148C; 300F)

Fabric Structure

Fabrics are flexible sheets of material constructed from textile fibers. The structure of fabrics depends on the way they are constructed, and affects their performance and suitability for use in masks. The three main fabric structures are: woven, knit, and nonwoven (Figure 2). 

Illustration of 3 fabric structures used in masks: a) wovens, b) knits, and c) nonwovens from Wange et al, 2020
Figure 2. Structures of fabrics used in masks: A) woven, B) knit, and C) nonwoven (Wange et al, 2020)

 

Woven Fabrics

Woven fabrics are created by interlacing fibers or yarns at right angles (90° angles) to each other in a ‘checkered’ pattern. This pattern is created by weaving (or interlacing) a set of horizontal fibers (weft fibers) over and under a set of vertical fibers (warp fibers). The properties of woven fabrics depend on the ways in which the fibers (warp and weft) are interwoven. 

Did you know? Woven fabrics are typically produced using one of the three basic weaves: Plain, Twill, Satin (Figure 3). All of the other types of the weave patterns are variations of these three basic weaves.

Illustration: The 3 Basic Weave Patterns for Woven Fabrics: Plain, Twill, and Sateen
Figure 3. Illustrations of the three basic weave patterns: 1) plain, with one yarn up and one down, 2) twill, with one yarn up, and three yarns down, and 3) satin, which is one yarn up and 4 yarns down. Image credit: Shamsuyeva, 2019)

 

For masks, fabrics with tighter weaves are usually recommended because they have smaller spaces between threads (smaller pore sizes) and provide more filtration. However, tighter weaves also have more resistance to air flow, which may decrease breathability. In general, the tightness of the weave of a fabric can be evaluated based on the thread count (measured by counting the number of threads in one square inch).

For fabric masks, both the CDC and the WHO recommend using tightly woven fabrics for absorbent mask layers. Examples of woven materials commonly used for face masks include:

  • Cotton Poplin (~100 – 130 gsm)
  • Quilting Cotton (~150 – 180 gsm)
  • Batik (~200 – 280 gsm)

Did you know?  Batik is a dyeing technique primarily done in Indonesia that traditionally utilizes fabrics with a high thread count.

An advantage of woven fabrics for masks is that they are commonly available and easily sourced. A disadvantage of woven fabrics is that the gaps between fibers (pore sizes) are large and regularly spaced, which can provide particles with a direct path from one side of the fabric to the other. To address these disadvantages, tightly woven fabrics are used to reduce pore sizes, and multiple layers of fabric with different weaves/orientations are used to prevent particles from having a straight path from one side of the mask to the other. 

Knit Fabrics

Knit fabrics are made by pulling loops of thread or yarn through each other to create a sheet of material. In general, knit fabrics are not recommended for use in masks because they are stretchy. When knit materials are stretched, it increases the size of the holes (pore size) in the materials, which decreases the its ability to filter particles. The WHO Guidance for COVID-19 masks (June 5, 2020) recommends against stretchy materials. 

However, knits are commonly available, and tend to be both breathable and comfortable and are sometimes used as non-filtering mask layers. An example of a knit fabric commonly used in masks is:

  • Cotton T-shirt Material (140 – 180 gsm): most t-shirt materials are knit

Did you know? There are two basic types of knitted fabrics: weft-knit (e.g., jersey) and warp-knit (e.g., tricot ). In weft-knit fabrics the loops are connected across the width (weft) of the fabric (Figure 4). Weft-knits are the most common and are used in things like t-shirts and socks. In warp-knit fabrics the loops are connected vertically (warp) through the fabric. Warp-knits are commonly used in underwear and stretch-pants.

Illustration: Weft Knit and Warp Knit fabric structures
Figure 4. Illustrations of the two basic knit patterns: 1) Weft Knit and 2) Warp Knit (Image credit: Fangueiro and Soutino 2011). Although knits (especially weft-knits) are not generally recommended for use in masks, advances in warp-knit fabric technologies have led to decreased pore sizes and properties that may be suitable for inner mask layers.

Nonwoven Fabrics

Instead of being woven or knit, nonwovens are fibrous webs that are bonded together to form a fabric, usually through mechanical, chemical, or thermal means.

According to international standards, “Nonwovens are structures of textile materials, such as fibers, continuous filaments, or chopped yarns of any nature or origin, that have been formed into webs by any means, and bonded together by any means, excluding the interlacing of yarns as in woven fabric, knitted fabric, laces, braided fabric or tufted fabric” (BS EN ISO 9092:2011)

In the context of masks, the most frequently discussed nonwovens are spunbond and meltblown nonwovens. The table below illustrates some of the pros and cons associated with spunbond vs. meltblown fabrics. 

Property Spunbond Nonwovens Meltblown Nonwovens
Filtration Capacity Lower Higher
Inhalation Risk Lower Higher
Fabric Strength/Durability Higher Lower
Washability (Melting Point) Higher Lower

 

Commercially available medical masks are usually constructed from a combination of spunbond and meltblown layers. Although meltblown materials offer better filtration compared to spunbond materials, meltblown materials are typically less durable and have lower melting points so are less suitable for re-use in fabric masks. In addition, meltblown fabrics are created from small discontinuous fibers that may pose an increased inhalation risk for people working with them at home (handling, cutting, and sewing); consider wearing an N95 while working with meltblown materials. For re-usable handmade fabric masks for COVID-19 we typically recommend spunbond nonwoven polypropylene materials.

Did you know? Synthetic fibers with diameters < 3μm (e.g., meltblown and nanofiber materials) may pose an inhalation risk to those working with them. Seek the guidance of regional health and safety officials and occupational safety officials when assessing fiber safety, and consider using N95s if handling meltblown and/or nanofiber materials. For fibers where potential inhalation risks are unknown, it is important to consider the known contributors to inhalation risk, the “3Ds”:

  • Dimension: Fibers < 3μm in diameter are small enough to penetrate deeply into the lungs and are more concerning than larger diameter fibers. Fibers that are < 3μm in diameter and > 5 μm in length are the most concerning.
  • Dosage: Higher quantities of penetrating fibers are more concerning than lower quantities.
  • Durability: Fibers that cannot be dissolved or broken down once in the lungs are more concerning than those that can.

It is well known that some fibers can cause lung disease and significant harm such as natural mineral fibers (e.g., asbestos) and synthetic mineral fibers (e.g., fiberglass and mineral wools (OSHA; CDC; WHO). When considering fibers for use in masks, it is important to consider potential hazards to the health of the end-user as well as that of the person constructing masks. 

 

When choosing nonwoven fabrics for mask use, look for virgin materials without adhesives or additives. For more information on using spunbond NWPP in masks for COVID-19 see Mask Fabrics: 201, see also The Big 4: Criteria for Community Mask Materials.

Mask Fabrics (photo): surgical mask on top of a stack of fabrics sometimes used in masks including spunbond nonwoven polypropylene (NWPP), heavy duty surgical wrap (SMS, H600), nanofiber material (Filti), and cotton denim material

Mask Fabrics: 201

In this section, we do a deeper dive into the characteristics of fibers and fabrics that are commonly used in masks. For fibers, we discuss fiber diameters, lengths, fineness, moisture absorption/resistance, melting points and electrostatics and their importance for masks. For fabrics, we discuss fabric weights (gsm) and do a deeper dive into the manufacturing processes for spunbond, meltblown, and SMS (spunbond-meltblown-spunbond) materials.

Fiber Characteristics 

Fiber characteristics affect filtration performance and suitability of potential mask materials. Fiber geometry (diameter and length), fineness, and moisture absorbance/resistance affect mask performance. For synthetic materials, melting points are an important consideration for re-use, and electrostatic properties can improve filtration. 

Fiber Diameter: In general, small diameter fibers are preferred for filtration because more fibers can be packed into a given area. This increases the effective surface area of fibers, which enhances mechanical filtration through Brownian diffusion, inertial impaction, and interception. CAUTION: synthetic fibers < 3 µm diameter (e.g., meltblown fibers and nanofibers) may pose an inhalation risk

  • Nanofibers are defined as fibers with diameters less than 1000 nm, although they are sometimes defined as fibers with diameters less than 100 nm. Nanofibers are commonly used for filtration, and occasionally used in sportswear textiles to improve water resistance. Polypropylene, Polyurethane (TPU) and PLA are commonly used materials for nanofibers. Although meltblown nonwovens can be created with nanofibers, the majority of nanofibers are created using electrospinning technologies.

Fiber Length: Shorter fibers trap more air, which may allow them to trap more particles, but also causes them to be more insulative and warmer. If you are making a summer mask, you might consider fabrics made from longer fibers.

Fineness (denier): Fiber fineness is measured in denier (a linear mass density). In general, lower denier fibers are considered softer and more comfortable. Lower denier fibers typically have better filtration characteristics, but they are more fragile and don’t stand up to the wear and tear of heavy use and frequent washing. Lower denier fibers may also have lower melting points than larger denier fibers of the same material.

  • Microfiber – Microfibers are defined as fibers with deniers of less than 1. For reference silk is usually 1 denier, and human hair is around 20 denier. The most common materials used for microfibers are polyester (PET), polypropylene (PP), and nylon (polyamides) are the most common types of microfibers.

Moisture Regain: Moisture regain is a measure of how much water a fiber retains. Fibers with 0% moisture regain are considered hydrophobic and may be appropriate for use in outermost mask layers. Synthetic hydrophobic fibers can also accumulate electrostatic charge, which can aid filtration. Fibers with larger moisture regain are considered absorbent, or hygroscopic, and may be more appropriate for use in innermost mask layers.

Table of Fiber Characteristics and Relevance For Specific Mask Materials

Numbers Terms Description & Relevance Examples
Fiber Length 2-46 cm Staple A fiber that is ≤100 times longer than it is thick. Shorter fibers tend to trap more air. • Cotton, Linen, Wool
• Manufactured fibers
>100 meters Filament A long continuous strand ranging in length from 100s of meters to kilometers. • Silk
• Manufactured fibers
Fiber Diameter ~10-50 µm Clothing Fibers Large diameter fibers are crisp, stiff, with poor drape; small diameter fibers are soft and pliable. In general, fibers < 10 µm are too fragile to create yarn and fibers > 50 µm are too coarse for comfort. • Natural fibers
• Manufactured fibers
• Spunbond
Spunbond fibers are continuous fibers of synthetic materials with diameters of 10-25µm • Polyester (PET)
• Polypropylene (PP)
• Polyethylene (PE)
<3µm Filtration Fibers Working with fibers <3µm may pose an inhalation risk since they can penetrate deeply into the lungs.
~1-3µm Meltblown fibers are typically <5µm synthetic staple fibers, though they may be formed as filament fibers. • Polyester (PET)
• Polypropylene (PP)
• Polyethylene (PE)
<1µm Nanofiber are defined as fibers <1µm in diameter, though historically were <100nm. They typically have lower melting points than larger diameter fibers of the same materials. • Polyurethane (TPU)
• PLA
• Carbon Nanofibers
Fiber Fineness (Thickness: Linear Mass Density) <1 -20 den Clothing Fibers Denier (den): mass in grams per 9000 meters of fiber (denier per filament, dpf, is used for multi-filament fibers) OR tex: mass in grams per 1000 meters of fiber. Higher values denier (or tex) values refer to courser fibers.
< 1 den Microfiber fabrics are defined as having a thickness of less than 1 denier. • Polyester (PET)
• Polypropylene (PP)
• Nylon (polyamides)
Water Absorbency (Moisture regain) 0-20% Moisture regain Moisture regain (%R): the conditioned, or wet, weight of the material (Wc, at 65% humidity and 70F), relative to the oven dry weight (WD) where %R = 100 x(Wc-WD)/WD
>1 Hygroscopic fibers have the highest moisture regain and are the most absorbent; common fibers are provided by SSTM DI909-77. • Wool (13%)
• Silk (11%)
• Cotton (7%)
≤1 Hydrophobic fibers do not absorb or adsorb water and are more conductive to the build-up of static electricity. • Polypropylene (0%)
• Polyethylene (0%)
• Polyester (0.4%)

 

Fiber Melting Points 

For manufactured fibers, melting point is an important consideration for washing and disinfection strategies for re-use. Fibers with melting points and glass transition points near 100ºC (212ºF) are not suitable for disinfection strategies based on boiling, steam, or hot water washing.

For additional details about how different fibers compare to each other, see the table below:

Fiber Type Diameter (µm) Length Fineness (denier) Moisture Regain (%) Melting Point (ºC)
Natural Silk 11 – 12 0.5 – 1.5 km 1 – 3 11 N/A
Cotton 16 – 20 10 – 65 mm 5 – 8 7
Linen 12 – 16 < 90 cm 9 – 36 8.8
Wool 10 – 50 4 – 7.5 cm 5 – 45 13.6
Asbestos 2 – 5 20 – 50 µm 1000
Manufactured Polyester (PET) 12 – 25 Filament or Staple 10 – 15 0.4 255
Polypropylene (PP; isotactic) 5 – 25 10 – 25 0 160
Polyethylene (PE) 5 – 25 10 – 25 110
Nylon (Polyamide) 12 0.7 – 20 4.5 215
Spandex (Polyurethane) 18 – 50 1.3 175
Acrylic (Polyacrylonitrile; PAN) 15 – 25 0.5 – 7 1.5 330
Carbon Fiber** 5 – 10 0.6 N/A
Activated Carbon Fiber 10 – 40 0.5 – 3 > 10%
Polylactic acid (PLA) <1 – 35 0.4 – 0.6* 130+
Polyurethane (TPU) <1 0.9 – 27 < 0.3* 175
Meltblown Fibers 1 – 3 < 0.6*
Nanofibers < 1
Fiberglass 6 – 20 Staple 0* 1121
Micro-glass 0.1 – 3

*Values not obtained from ASTM D1909-77.

** 90% of carbon fibers are made from PAN.

Fiber Electrostatics

Static electricity or surface charge can provide additional filtration by repelling charged droplets or particles. This electrostatic filtration does not impact breathability and is typically a key factor in the filtration efficiency of N95 masks.

Static electricity can be generated by rubbing materials together to transfer electrical charge from one material to another. For fibers and fabrics, the electrostatic propensity of the material is defined as “the capacity of a given textile material to acquire and hold on electrical charge by induction (via corona discharge) or by tribo-electric means (rubbing with another material)”(ASTM D4238-90). Fibers with low moisture regains (i.e., hydrophobic synthetic materials) can hold electrical charge much longer than absorbent materials.

The triboelectric series table below categorizes fibers by their charge, from most strongly negative to most strongly positive. Hydrophobic synthetic materials such as polypropylene, polyester, and polyurethane are expected to be able to generate and hold electrostatic charges longer than other materials, which makes them ideal filtration layers for mask making.

Material Polarity Moisture Regain Fiber Origin
Polyethylene (PE)

0 Hydrophobic Synthetic
Polypropylene (PP) 0
Polyester (PET) 0.4
Polyacrylonitrile (PAN) 1.5
Cotton 0 7 Absorbent; Natural
Wool

+

13.6 Absorbent; Natural
Nylon (PA) 4.5 Absorbent; Synthetic
Silk 11 Absorbent; Natural
Polyurethane (PU) 0.3 Hydrophobic Synthetic
PLA 0.4

 

Fabric Weight and Thread Count

Although fabric weights and thread counts are not stand-ins for filtration and breathability characteristics, they may help mask makers get a general sense of fabric suitability for use in masks.

Fabric Weight (gsm). A standard measurement for fabric weight is grams per square meter (gsm) or ounces per square yard (oz/yd²). The higher the gsm weight of the fabric, the more dense it is. Generally, a lightweight fabrics is between 20-150 gsm, medium weight is 150-350 gsm, and heavyweight fabrics will be 350 gsm or more. 

Material Weight GSM Type of Fabric Fabric Use
Lightweight 20 – 25 Medical grade spunbond NWPP Disposable medical masks
30 – 40 Spunbond NWPP Interfacing Used as an inner layer to give materials added structure
50 – 100 Gauze, chiffon Blouses and skirts
70  – 110 Spunbond NWPP Reusable bags
100 – 140 Cotton Poplin Shirts
140 – 180 Jersey Knit Cotton T-Shirts
Midweight 150 – 180 Quilting Cotton (65 – 120 threads per inch) Quilts
170 – 230 Knit, linen, cotton/spandex blends Pants, lightweight jackets, dresses
200 – 280 Batik Cotton (220 threads per inch) Quilting, dresses, home decor
230 – 340 Stretch denim, canvas, sweatshirt fleece Pants, jackets, sweaters
Heavyweight 340 – 450 Rigid denim, canvas Jeans
450 – 650 Cotton Towel Face towels, bath towels, pool towels

For fabrics with the same structure and composition, fabrics with higher weights (gsm) are likely to provide higher filtration (and lower breathability) than those with lower weights/thread counts. For example a 180 gsm quilting cotton is likely to provide more filtration than a 120 gsm cotton poplin. However, the gsm between quilting cotton and spunbond nonwoven polypropylene can not be directly compared due the difference in material structures (nonwovens typical have better filtration than wovens) and the different densities of the fabric fibers (cotton fibers have a higher density than nonwoven polypropylene fibers).

For multi-layered masks made of spunbond NWPP, we recommend using three layers of 65 – 100 gsm material (e.g., a combined total of 195 – 300 gsm), however for increased breathability/comfort in lower risk situations masks with two layers or masks with multiple layers of lighter weight materials targeting total weights of between 120 – 300 gsm (e.g., four or five layers of 40 gsm, or two or three layers of 65 – 100 gsm) may be appropriate. In general, increasing the number of layers and weights of materials increases filtration, but decreases breathability. Optimal layering combinations will vary depending on use, and specific material manufacturers/sources. Verify comfort, breathability, and wearability before use. 

Thread Count. To dive a bit deeper into thread counts (described briefly in Fabrics 101), thread count is a common metric for woven fabrics such as bedsheets. It refers to the combined number of horizontal (weft) and vertical (warp) threads per square inch of fabric. Generally, the higher the thread count or TPI (threads per square inch), the softer the sheet, the denser the weave, and the better the material is for masks. However, the practical amount of thread that can fit into a square inch of fabric is limited, suggesting that items above 400 TPI may be counting the number of strands in a twisted yarn to inflate their thread count claims.

In general, fabrics with higher thread counts provide better filtration than those with lower thread counts. For masks, American Association of Textile Chemists and Colorists (AATCC) suggests that woven (plain, satin, sateen, twill) fabrics with thread count of 400 or more may be acceptable for mask layers.

Fabric Testing Standards for Manufacturers

Fabric Testing Standards. In addition to GSM and TPI, a number of additional fabric testing standards may be useful for mask manufacturers to consider to better characterize fabrics for use in masks. The table below lists some of the potentially relevant test metrics as well as standardized test methodologies for each.

Test Standard Method Measurement Equipment
Fabric GSM ASTM D3776 GSM cutter, specimen fabric.
Yarn Count ASTM D1059/1907 Electric balance, Counter pin, magnifying glass
Fire Testing ISO-14116 Gas lighter and fabric.
Dimensional Stability to Washing Test AATCC 135 Measurement Scale, Washing machine, Tumble dryer.
Fabric Allergy Testing AATCC 81 pH Meter
Fabric Damage Testing ASTM D1424 Tear strength tester.
Seam Slippage Test ASTM D434-95 Strength tester machine, Sewing thread and needle.
Fabric Abrasion Testing ISO 12945 Abrasion tester, Scissor, Electric Balance.
Fabric Absorbency Test ASTM D123–01 Fabric, Water.
Shrinkage Test ISO 6330 Washing machine, Shrinkage test Scale.

NISTIR 8115: A Guide to United States Apparel and Household Textiles Compliance Requirements. 

AATCC MXXX-2020 Guidance and Considerations for General Purpose Textile Face Coverings: Adult DRAFT VERSION: 1.0 DATE: JUNE 1, 2

Fabric Characteristics: A Deeper Dive Into Nonwovens

As discussed above, nonwoven synthetic fabrics are typically used in commercial medical masks, due to their balance of filtration and breathability, water-resistance, and ability to support electrostatic surface charging (e.g., electret and corona charging). In the context of masks, three types of nonwovens are typically discussed: spunbond nonwovens, meltblown nonwovens, and electrospun nonwovens.

Spunbond and Meltblown Nonwovens

The manufacturing processes for spunbond and meltblown nonwovens both start with a process called spunmelt, but then diverge to yield different types of fibers with different properties. 

Spunmelt creates nonwoven webs by heating thermoplastic polymers (e.g., polypropylene, polyester or nylon) and extruding them through a metal plate with hundreds of holes in it, known as a spinneret. This extrusion process is similar to a spaghetti press or garlic press: the materials are pressed through a grate to create string-like fibers. 

Nonwoven Manufacturing Showing Synthetic Fibers Coming out of a Spinneret
Figure 5. The majority of manufactured fibers are made by pushing a solution of raw materials through a spinneret. The spinneret separates the solutions into individual streams which are then solidified into fibers. The size and shape of the holes in the spinneret affect the resultant fiber diameters and shapes. Image Source: Arville

Spunbond Nonwovens

Spunbond fabrics are produced by extruding melted polymer through a spinneret to form long thin filaments. These filaments (5 – 20 um diameter) are collected on a moving conveyor belt, where they form a fibrous web. The web of nonwoven fibers is then passed between two heated rollers, which thermally bond the web together to give it better strength and durability. This process is called thermal bonding or calender bonding (Figure 6).

Schematic of Spunbond Nonwoven Polypropylene Manufacturing Including Calender Bonding which leaves the characteristic dimpled pattern
Figure 6. Schematic manufacturing process for spunbond nonwoven fabrics: spun-laying and fabric formation using thermal bonding method (calender bonding), which gives spunbond nonwovens the characteristic dimpled pattern. Image source: MakerMask.org

 

Some of the advantages of spunbond nonwovens are that they are more durable than meltblown materials, have higher tensile strengths, are less likely to pose inhalation risks (larger diameter, continuous fibers), and typically have higher melting points relative to meltblown materials made from the same polymer.

Common spunbond materials used in masks include:

  • Spunbond nonwoven polypropylene (PP): common, cheaper to produce, easier to spin with smaller fiber diameters than spunbond polyester. 
  • Spunbond nonwoven polyester (PET): less common, more expensive, not possible with recycled fibers, better strength and durability, and dyeable
  • Spunbond nonwoven polyethylene (PE): lower melting point, not compatible with high temperature washing or disinfection. NOT SUITABLE FOR REUSABLE MASKS

Meltblown Nonwovens

Meltblown nonwovens start off with a spunmelt process similar to that of spunbond fibers. However, the process after filaments are extruded from the spinneret is different. For meltblowns, the extruded fibers are are immediately subjected to high velocity hot air streams coming from both sides of the spinneret. These rapidly moving streams of hot air hit the molten polymer at the edge of the spinneret and blow it into very fine filaments (~1 -5 μm diameter). The rapidly moving air causes these fibers to break into shorter, discontinuous filaments, which are then randomly dispersed and collected into a web on the roll below. 

Meltblown fabrics have many ultrafine fibers for a given weight and create fabrics with large surface areas, which yields excellent filtration properties as well as good insulating properties. However, meltblown NWPP tears easily, is harder to sterilize, and may pose an inhalation risk.

Although made from the same raw stock as spunbond NWPP, the structure of the meltblown material, and the size of the fibers are different. The individual fibers of meltblown NWPP are both shorter and thinner, which increases the risk of particle inhalation. For large-scale commercial mask operations with appropriate manufacturing controls and oversight, these risks can be mitigated; however, the use of meltblown NWPP in DIY masks is not recommended at this time.  

Composite spunmelt Materials (SMS, SMMS, et al)

Spunbond-meltblown-spunbond (SMS) materials are multi-layered fabrics, commonly used in medical gowns, drapes, and sterilization wraps. The spunbond layers give the materials better structural integrity, and the meltblown layers give it better filtration. An example of an SMS material is the Halyard series of blue sterilization wraps, available in weights from H100 to H600.

Image: Composite Spunbond Meltblown Spunbond Fabric (source: Halyard)
Figure 7. Schematic of SMS (Spunbond-Meltblown-Spundbond) Fabric (Image Source: Halyard)

 

As mentioned above, meltblown materials generally stand up poorly to cleaning and disinfection. Because SMS includes meltblown layers, care should be taken when exposing materials to heat or agitation. Such materials may be better suited to single-use masks.

Electrospun Nonwovens

The majority of nanofiber materials are manufactured through a process called electrospinning. For electrospun fibers, the precursor materials go through a spinneret, but instead of being blown by hot air as in meltblown processes, electrical fields are used to draw out, and deposit extremely thin (1 nanometer to 500 nanometers in diameter) continuous fibers (Figure 8).

Electrospinning for Nanofiber Materials
Figure 8. Electrospinning diagram. Image Souce: Joanna Gatford – The New Zealand Institute for Plant and Food Research Ltd

Electrospun fibers tend to be fragile on their own, so are usually deposited on a stronger substrate material like spunbond fibers to create composite nonwovens. Although electrospun fibers of frequently created from synthetic materials, they can also be created from ‘natural’ plant and animal based materials like silk and cellulose. These ‘natural’ fibers are biodegradable, and in the future may be able to be used in create more environmentally friendly disposable nanofiber filtration materials for masks.

Did you know? Materials, like Filti are composite materials with spunbond layers to enhance strength and durability and nanofiber layers to enhance filtration. 

Conclusion

This two-part post explored some of the basic properties and characteristics of fibers and fabrics used in mask making. Note that each fiber type and fabric type has its pros and cons. Our research points to the utility of multi-layer masks with synthetic nonwoven outer layers, with each layer contributing to a balance of filtration, breathability, and washability. Always be aware of the safety profile of the materials in your masks and the directions for their care and use. 

REFERENCES

Types of Fabric: Woven, Knit, Nonwoven
  • Wang, Wei & Li, Tao & Liu, Kang & Wang, Shuo & Peng, Huaxin. (2020). Effects of three fabric weave textures on the electrochemical and electrical properties of reduced graphene/textile flexible electrodes. RSC Advances. 10. 6249-6258. 10.1039/C9RA08524F.
  • Fabric Types: <iframe width=”900″ height=”506″ src=”https://www.youtube.com/embed/HrFBiniEyUI” frameborder=”0″ allow=”accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture” allowfullscreen></iframe>
  • Knit Fabrics: https://akaspar.pages.cba.mit.edu/machine-knitting/
Nonwovens
Fibers
Electrostatics
  • Perumalraj R. Characterization of Electrostatic Discharge Properties of Woven Fabrics. Perumalraj, J Textile Sci Eng 2016, 6:1 DOI: 10.4172/2165-8064.1000235
  • Edward R. Frederick (1974) Some Effects of Electrostatic Charges In Fabric Filtration, Journal of the Air Pollution Control Association, 24:12, 1164-1168, DOI: 10.1080/00022470.1974.10470030. https://www.tandfonline.com/doi/pdf/10.1080/00022470.1974.10470030
  • Havenhill, R.S. , O’Brien, H.C. , and Rankin, J.J. , Electrostatic Properties of Rubber and GR-S, J. Applied Phys. 15, 731-40 (1944).
  • ASTM D4238-90, Standard Test Method for Electrostatic Propensity of Textiles (Withdrawn 1996), ASTM International, West Conshohocken, PA, 1990, www.astm.org

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Homemade Mask Summit: Masks Unmasked https://makermask.org/homemade-mask-summit-masks-unmasked/?utm_source=rss&utm_medium=rss&utm_campaign=homemade-mask-summit-masks-unmasked Mon, 20 Jul 2020 23:26:37 +0000 https://makermask.org/?p=1164 In June 2020, the team coordinating the Homemade Mask Virtual Summit at Tulane University interviewed Dr. Songer about the science behind masks and invited Dr. Songer to give the Keynote Address for the summit. This post contains the audio and transcripts of Dr. Songer’s Keynote Speech: “Masks Unmasked: A Look at the Science Behind Fabric […]

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In June 2020, the team coordinating the Homemade Mask Virtual Summit at Tulane University interviewed Dr. Songer about the science behind masks and invited Dr. Songer to give the Keynote Address for the summit. This post contains the audio and transcripts of Dr. Songer’s Keynote Speech: “Masks Unmasked: A Look at the Science Behind Fabric Masks for COVID-19” as well for the two interviews with Dr. Songer for the JustWannaQuilt Podcast. The “Homemade Mask Guide“, created in collaboration with both scientists and sewists after the summit is also included.

Keynote Address for the Homemade Mask Summit

Speaker Introduction: Dr. Jocelyn Songer is the founder of MakerMask.org, a group of volunteers providing science-based mask information and designs to community mask makers by studying and testing them. She holds a BS and MS in Biomedical Engineering from Worcester Polytechnic Institute and a PhD in Speech and Hearing Bioscience and Technology from MIT.

Slide: Masks Unmasked: A look at the science behind fabric masks for COVID-19, Dr. Jocelyn Songer, June 17, 2020. Illustration: MakerMask: Surge, MakerMask: Cover, MakerMask: Fit from MakerMask.org

 

Audio: Keynote: Masks Unmasked: A Look at the Science Behind Fabric Masks for COVID-19
Transcript: Keynote: Masks Unmasked: A Look at the Science Behind Fabric Masks for COVID-19

Keynote: “Masks Unmasked: A Look at the Science Behind Fabric Masks for COVID-19”

Dr. Jocelyn Songer

June 17, 2020

Keynote Speech Transcript

This has been edited for clarity and brevity. Each numbered subheading refers to a slide number

Audio Available at: https://www.spreaker.com/user/10136802/hmms-part-1-6-18-20-11-06-am

Introduction

1.   Masks Unmasked (Illustration: 3 MakerMask Designs)

It was really fun listening into the last couple talks. I absolutely agree that masks are awesome and that perfect is the enemy of the good. That’s something I remind myself all the time; it’s not worth trying to make things perfect if you can’t get anything done. So the masks and emergency equipment that you have with you that you’re willing to wear is always going to be the best mask.

2.    Thank You! (Illustration: Sewing Superhero)

Sewing Heroes Illustration: Thank you to sewists from Dr. Jocelyn Songer and MakerMask

I just wanted to say thank you “sew”, so much. None of us expected for sewists to be put on the front lines of equipment that everybody needs to be safe from this pandemic. But when global supply chains failed, sewists and others stepped up. I wanted to put in here how many masks we collectively have made. It highlights a little bit of the challenge with the science because it’s really hard to get solid numbers on that. At least, I wasn’t able to. It was like 70,000, 80,000, 100,000, but we don’t have any good totals of how many masks are out there that we’ve made, what they’re all made of, and all of that. But anyway, thank you “sew”, so much; you are true heroes of this pandemic and of 2020. I appreciate you and I know everyone else does as well.

My Story

3.    My Story: A culture of Sewing (Vintage Postcard: Sewing in Orange c. 1880)

Image of Vintage New Home Sewing Machine Post Card and Text

I am from a small town called Orange, Massachusetts. It is the home of New Home Sewing Machine. They started manufacturing sewing machines in my town in 1860. So sewing was a part of the culture that I grew up in. My grandma was a seamstress; my mom sewed all my clothes for me as a kid; she also sewed my prom dress and my wedding dress. I don’t think of myself as an awesome sewist, but I don’t remember a time when I didn’t know how to sew. My mom and my grandma constantly lecture me to stop sewing with a lead foot – if I want straight seams, I have to slow down.

4.    My Story: Science & Engineering (Photo: Dr. Songer in the OR)

Photo of Dr. Songer in the OR wearing a mask and working on biomedical devices

I know Whitney gave me a great introduction talking about my background as an engineer. I also have a background as a first responder; I used to be an EMT, and I maintain a current first responder training. So I never leave my house without some personal protective equipment and masks in general. I always have a sewing kit.

5.    My Story: Occupational Asthma (Photo: Dr. Songer on Mt. Katahdin, AT 2013)

Dr. Songer Standing on the Summit of Mt. Katahdin after her successful 2013 Appalachian Trail Thru-Hike

I was going along with my life in academia between engineering and biomedical stuff, and I developed occupational asthma; I was literally allergic to my job. So then instead of just having to use masks for work, I had to wear them for my own health. I got fitted with N95s and took contamination showers every day, but it wasn’t quite enough. My pulmonologist gave me a choice: I could either keep breathing or keep my job. So I left my job to go hike the Appalachian Trail and get my health back.

6.    My Story: Backcountry Masks (Photo: Dr. Songer on PCT and CDT with Masks)

Photo and Text: Dr. Songer wearing a bandana mask during forest fires on the PCT (top), and Dr. Songer wearing a Vogmask for the smoke and fires on the CDT in 2018

That is when I first started having some MacGyver masks and figuring out how to make a face mask that would filter smoke. Because while I was out backpacking the Pacific Crest Trail and the Continental Divide Trail, there were massive forest fires. I didn’t have access to supply chains for face masks because it would be another five days until I get to town. So I had to figure out how to make do with what I had. So I used two layers of my bandana hoping that it would work to filter out some of that smoke. It doesn’t work very well. So that sort of forced me to start improvising through other options with the materials and fabrics I had.

Then when I got off the trail, I did a whole bunch of research on masks and what the ideal combinations were. I think I purchased every single reusable facemask that was on the market at the time. So now I have a stack of all these different reusable facemasks, and I kind of had a sense of what did and didn’t work and what I liked and didn’t like. Masks with exhalation valves work well in a lot of situations like forests when you’re dealing with smoke; they don’t work great for infection control. What we’re using masks for now is to keep our germs to ourselves, essentially, and the exhalation valve just spews everything past the filter into the environment.

When we started to see supply chain shortages, I started working with my mom who’s an RN and a risk manager on researching and designing masks for COVID-19; trying to figure out what the best available information was and how to move forward; make sure that we could get these masks out to the loved ones in our community.

COVID-19 and Masks: Overview

7.    Research on Handmade Masks Pre-COVID (Photo and Data from Research)

Dato Cloth Mask Pattern and Rangasamay Data on Mask Materials

If you were doing research on handmade masks before COVID, you probably came across the same two studies: The one the CDC pointed everyone to that said it’s possible that we might end up wanting masks and not be able to get them in a pandemic – which turned out to be prophetic – and they gave this one pattern. In all of the literature at the time, I could only find one pattern for a handmade mask for an eight-layer cotton t-shirt mask. Calling it a pattern was perhaps a little bit of a stretch. It’s a picture of how they did the ties on it and sort of mentioning how they crisscrossed the t-shirt layers. That was the primary article the CDC cited. There was another one saying: Here are your fabric options: sweatshirt, t-shirt, towel or scarf.

Of those, they said the towel would be the best. I thought we had to be able to do better than a towel because towels wrapped around your face are not easy to breathe through and work with. If you’ve had the experience of hiking 100 days through the desert with a facemask, you’ll know that there’s a whole lot more to a facemask than whether or not it can pass a particle count; you have to be able to wear it, and wearing a really heavy, bulky mask for long periods of time isn’t practical for most people. So I looked at that research and said let’s see if we can do better. The next thing that was important was seeing what we knew about how COVID was being spread.

8.    COVID-19 (SARS-CoV-2) is primarily transmitted via respiratory droplets

Illustration of Droplet-Based Transmission of COVID-19

The WHO, CDC and all the research we have so far suggests that COVID-19 is primarily spread via respiratory droplets. There’s a figure here that was originally for Ebola but is also true for COVID showing that the droplets spread around six feet. If you’re talking about something that is airborne and truly aerosol driven, the distance that you’re talking about is 30 feet instead of 6. So the main thing we wanted our masks to do was to block droplets.

In Healthcare Settings, Medical Masks are Used for Droplet Precautions

I know that the previous speaker was talking about focusing on masks for the general public and not on the kinds of masks that you need in healthcare settings, and I was kind of interested in bridging that gap. Right now in healthcare settings, medical masks are used as droplet precautions. What that means is that depending how a disease is transmitted, there are different recommendations and guidelines for the precautions that you need to take so as to keep you safe as well as your patients.

So, the kind of mask that is suggested for things that are droplet-based is usually a surgical mask because they block those large droplets that we were talking about.

9. Anatomy of a Mask

Illustration: Fabric Mask showing ear loops, nose bridge, mask materials

Flexible nosepiece to help get a better fit across the bridge of the nose; ear loops (must be latex-free because a lot of elastic has latex in it and a lot of healthcare providers have latex allergies); body of the mask.

A lot of the dialog focuses on particle filtration, but for droplet precautions, fluid resistance is a key component of the mask requirement, as is breathability. The way that you test this if you’re trying to attain a surgical mask certification is with blood – synthetic blood at 80mm mercury pressure sprayed at it. So one of the things that I’m hoping to get dialog on with some of the regulatory agencies is setting up standards that are not surgical masks so you don’t have to have it withstand 80mm of mercury blood, but they’re still fluid resistant. If you’re getting sneezed or coughed at, or somebody spits at you, it’s not coming at that same high pressure.

I see a lot of masks online and in the news that are worn upside down where the pleats are backwards. The waterfall pleats should fall away from your nose. If the mask is upside down, that leads to the possibility of things getting caught up in those pleats instead of falling off and away from them. I call those tide pool pleats because they gather things inside the mask.

10.  For the General Public, Fabric Masks are Used to Prevent the Spread of Droplets

Illustration: Social Distancing and Use of Cloth Masks

When we’re looking at facemasks for the general public, the WHO and the CDC now agree that we should be using facemasks in general and that these facemasks are designed to prevent or reduce the spread of COVID-19. So you place your face covering on to protect other people, and they place their face covering on to protect you. So that’s the intended use for facemasks now. The FDA says that when you’re talking about fabric masks and cloth face coverings, you should remind people that they’re not replacements for social distancing and hand hygiene.

11.  Research: Face Masks Help Reduce the Spread of COVID-19!

Slide:Data Supporting the Use of Fabric Masks

In just the last couple weeks we’re getting some studies coming out that say yes, indeed, the facemasks are working. Not only do medical masks help but cloth facemasks and fabric masks also help. A study of 172 articles is what made the WHO change their mind and say yes, we do recommend fabric masks.

Just within the week we got this new study saying that wearing a facemask in public corresponds to the most effective means to prevent human transmission of COVID-19. That is pretty huge. They show that within a month, 70,000 infections were prevented in Italy and 66,000 in New York. Looking at these graphs, on the left there’s a picture of data from the US that shows the effect of social distancing at flattening the curve, and on the right they show the data from New York City which shows that instead of just flattening the curve, putting in the facemasks requirements and getting people to adopt facemasks on a large scale crushed the curve; instead of being flat, you got a decrease in infection.

So, the fabric masks that we’ve been making, they have helped and they are helping. The data is finally coming through showing that. We are making a difference, and that is awesome and important.

Mask design Requirements

Illustration: MakerMask Designs

12.  My Fabric Mask Requirements: Water-Resistant, Breathable, Washable, and Latex-Free

I founded MakerMask. My mom and I designed some masks as we were going through the options. The requirements I was looking for were that they be water resistant, breathable, washable and latex-free. The big difference there compared to most medical masks is washable, because in healthcare settings masks are traditionally single use. That’s led to some interesting design features. One big challenge because I was looking for water-resistant materials was balancing water resistance and breathability because those two things do not usually get along; waterproof is not breathable, and breathable waterproof materials aren’t really waterproof. So that’s an interesting tradeoff. From my backpacking experience I had already done a bunch of research into different fabrics where you can get this tradeoff.

13.  Spunbond Nonwoven Polypropylene

Image: Spunbond Nonwoven Polypropylene for Fabric Masks for COVID-19

I ended up landing on nonwoven polypropylene. Spunbond is the kind of polypropylene you’re looking for, and we like it synthetic not woven. That combination allows it to be breathable, which is good. Nonwoven structure helps with filtration; nonwoven materials tend to be better at the mechanical filtration component. The nonwoven polypropylene (NWPP) materials are water resistant; they’re naturally hydrophobic. The spunbond nature of the fabric has better structural integrity and is continuous fibers. A lot of you who’ve been paying attention to mask filter materials have probably heard about meltblown polypropylene as well, which uses smaller, more discontinuous fibers that don’t hold up to washing. The fibers can shrink and compress, and you lose breathability. So that’s how I ended up with that spunbond NWPP. The other advantage to the NWPP at the time was that I had it lying around the house; I could source it from reusable grocery bags that I had or from a whole bunch of other options.

14.  CDC Guidance on Cloth Face Masks

Illustration: Cloth Masks from the CDC

I could give a three-hour talk just on NWPP, how it’s made, it’s features. Ideally, we would be using medical-grade NWPP, which we can’t get because of global sourcing issues. My next criteria was food-grade NWPP because it’s designed to touch food and gives you some better hazard analysis parameters, essentially. There are other materials that are heavier and others that look similar that aren’t quite as good, so you need to make sure you check breathability. Maybe we can find a time to talk about all the dos and don’ts of how you go about making those finer choices.

On the CDC’s webpage, they say masks need to be multilayer. They’re recommending tightly-woven cotton. All of their designs are cotton, which is an absorbent material, which is good at containing your droplets and keeping them to you. I don’t want to talk about their bandana mask design because it drives me nuts.

So, it has to be multiple layers; you should check to make sure it’s breathable and washable. The FDA requires that you include a label in the skin-contacting material with washing and disinfecting instructions.

WHO Guidance on Fabric Masks

15.  WHO Guidance on Fabric Masks

Image of 3 Layers of Fabric Masks for COVID-19

There is a lot of discussion about the WHO guidance and why they recommend what they do. They recommend at least three layers of mask materials with an outer-most layer that’s hydrophobic (water resistant. The way people measure it is by looking at how well water beads up on the surface of the material. If you can see a full bead of water sitting on top of the material, that’s hydrophobic; if water absorbs into the material like a paper towel, that’s hydrophilic. Hydrophobic and water resistant tend to mean the same thing, and hydrophilic and absorbent mean roughly the same thing as well. Synthetic materials, for the most part, are hydrophobic. Silk and cotton fibers are hydrophilic. Flicking a bead of water at it is the way I tend to make my first approximation. Pour 5ml of water from a teaspoon to see if it drains through within 60 seconds is the more quantitative way of assessing that.

When the WHO guidance is saying polypropylene or polyester, those materials are selected because they’ve tested them and they have that hydrophobic property in the threads. If you have a knit t-shirt with holes in it that’s made out of polypropylene or polyester, even though the fibers don’t absorb water, the material isn’t water resistant so the water can go through the holes.

Elizabeth Townsend Gard, Host: So if you’re shopping somewhere like Jo-Ann’s, they’ll say what it’s made out of, so this is very helpful in terms of moving forward. So this is doable for us as sellers.

Songer: Absolutely! We have already talked for 2.5 hours and this is another half an hour, but I would love to gather information and have some more conversations so we can bridge some of the communication gaps across the communities.

ETG: One of the things is to put out a Best Practices for the sewing community that’s very short and simple but helps people understand how to pick the fabric and what the key things are. I’d love for you to work with us on that. It’s basically what you’re doing but put it into sewing language so that we can actually have this discourse. I really do believe that you help us make this very difficult bridge between the science and the sewing community.

Songer: For that outermost layer with the waterfall pleats, if you can, you want things to hit it and drop down and away instead of getting absorbed into the mask and held close to your face. So the goal of the outer-most layer is to prevent things from going into the absorbent layers. The WHO is specific in suggesting that the outer-most layer be hydrophobic. That’s a pretty major difference from the recommendations we were seeing before this new guidance. Those were 100% focused on source control – containing the user’s droplets. That’s still the intended use for all of these masks, but it’s raising the possibility that you might actually be able to prevent at least some stuff from coming through the other way.

For the middle layer, you can go either way. They say either use a hydrophilic layer like cotton or a cotton blend that will absorb the user’s droplets or use a hydrophobic nonwoven material which will enhance filtration. They say that because nonwoven materials have a much more chaotic structure and do better at mechanical filtration than woven materials because woven materials tend to have holes that go straight through in a more organized way. So if you’re used to doing materials at different angles, that mismatch of how the fibers are formed together gives you better filtration. There’s lots of literature on the different nonwoven materials, but that’s the rationale there.

For the inner-most layer in masks for general use and for surgical masks as well, that is designed to contain user droplets. So, they recommend a hydrophilic or more absorbent material like cotton.

16.  WHO Fabric Masks: Choosing Fabric Materials

Graph: Image from Zhou et al Showing Fabric Mask Materials Q Values for Filtration

One of the differences between the guidance we got from the CDC and what we’ve heard from the WHO is that the WHO starts giving us actual criteria for how we should be choosing materials for fabric masks. The reason why they select among NWPP, polyester and cotton in specific is because of a new study that came out in ACS showing the balance between filtration and breathability – those two things can be measured separately, but in order to kind of look at them both together, they ask you to look at the filter quality factor because that combines both metrics in one. So, the higher the Q value, the better. You want Q values for the materials you’re using to be greater than 3. That is a criteria that we can look for to have a good balance between filtration and breathability. Because if you can’t breathe through it, it doesn’t matter how good the filtration is; you can’t use it in a mask.

They show the Quality factor for three different cotton materials, a silk material, nylon (which doesn’t do very well at all,) and polyester, and spunbond nonwoven polypropylene. For each material, they show the initial value off the shelf, and then they check to see if you can improve Q values with an electrostatic charge. You can think about it as static electricity. That’s what they test in this particular study. Back in high school/college physics, you’d do demonstrations rubbing materials against a rubber rod and build up a charge on it and then show that the material gets a static charge and keeps it for some amount of time. When you do that with cotton, it doesn’t build up and hold an electrical charge; if you do it with a hydrophobic material like polyester or polypropylene, not only does it hold a charge initially; it can keep the charge. Polypropylene was able to do that for longer than anything else. That allows it to be better at filtering. The thing that was most interesting about that electrostatic charge part is that they show that even when it started to get humid, the charge on polypropylene remained for over an hour. So it’s possible that there might be some practical applications for home users being able to electrostatically charge their masks. As an electrical engineer, it’s fascinating; I’m really interested to see how that pans out long term.

ETG: I don’t really understand how it only lasts an hour. How are you supposed to recharge it? Are you supposed to have a bunch of masks with you?

Songer: I think that’s a fair concern, and it’s something I’m not sure about, either. They were showing that if you had a pair of vinyl or latex gloves and you rubbed your polypropylene mask between them, it would build up a static charge that was big enough that even at body temperature and humidity, you got the benefit of that for at least an hour. They didn’t show us data about what happened beyond the end of that hour. We don’t have information on how quickly that can cause a mask to break down because rubbing materials tends to cause them to break down faster. So that electrostatic component for home users I think is still an amazing, wonderful, fun theory, but the practicality of it still needs more consideration. But I think for instances where you’re going to go out for 15-30-60 minutes to run errands, and then you’re going to go back to your safe environment, it may be useful. More testing is needed. If you’re going to be wearing a mask for four hours, then that electrostatic boost you get isn’t likely to stay with the material the whole time. I looked at the data they have for the decay over time. It’s promising, but it needs more practical consideration.

Even without that electrostatic boost, the Q value for the nonwoven polypropylene is still the highest of all the others. The Q values that I mention in the summary are without the electrostatic charge. So that puts NWPP on the top of the list, cotton next, and then polyester somewhere in between. The nylon wasn’t breathable enough, so that’s why they voted no on that. The silk didn’t have enough filtration for them.

17.  WHO Fabric Masks: Choosing Layering Combinations

Text: WHO Fabric Masks: Choosing Layering Combinations

Since early March, the very first thing I wanted to do was to get my mask designs tested. I did some basic hazard analysis to see if there were any obvious pitfalls because I wanted to make sure things were safe. There wasn’t any guidance on the ideal mask and what we should be aiming for in terms of testing criteria for fabric masks. The WHO guidance provides us some standards which we should be trying to adhere to in the design of our masks.

The WHO recommends at least three layers. A big part of that is adding that water-resistant, hydrophobic material to the outside. So, if you have a whole bunch of cotton masks and want to bring them up to WHO requirements, the only thing you need to do is add a mask cover of NWPP.

In terms of filtration, they say that for private masks for general use you should be aiming for 70% filtration efficiency. It’s nice to have some numbers there for what’s reasonable to get. For breathability, they suggest that you need less than a 40 Pascal pressure drop across the mask. That’s not easy for us to test at home. I have some data that I’ll share which shows that cotton masks and the cotton-NWPP combinations that we’re using do meet those criteria. For home users, I recommend putting your materials on the end of a toilet paper tube and blowing a ball of lint through them so you can test the breathability without having to put the mask up to your mouth and sucking air through it.

For the filtration, we don’t have access to the fancy equipment that the big testing labs do; we do, however, have access to our kitchens. For a lot of food stuffs, they have to calibrate the size of the particles. For those of you who both bake and sew, you know that having your baking soda and flour and baking powder at the right density makes a difference. Baking powder has particle sizes calibrated at less than 50 microns. You can find things in your kitchen with particle sizes down into some of the smaller-micron particles that are relevant. It can give you a sense of how well they’re doing. If I take the same toilet paper tube that I use for the breathability test and put it over the end of the material, for loosely-woven cottons you’ll see that the baking powder just shakes right through and makes a mess if you’re doing it on a piece of black paper. If you use a more tightly woven cotton, or two layers of it, or the NWPP, you can see that you don’t get as much going through. There are a bunch of other DIY home tests that people are looking at to try to get at that same small particle filtration.

Mask Care, Cleaning, and Disinfection

ETG: This is just the beginning of the conversation. We have questions about all kinds of other materials. We are going to be working with you if you’re willing to help people understand what these tests are and start to really think about the combination of fabrics that are out there as far as filtration, breathability and cost.

Songer: We’re designing fabric masks to be reusable and washable, and that’s a pretty big difference from what we’ve seen in the medical-grade masks. The WHO guidance references a French standard, which says that you need to make sure that your masks can hold up for at least five washes. That’s kind of a minimum for reusability. Then they suggest you need to be able to wash it at temperatures of at least 60C. I could give a whole talk on just the washing, cleaning and disinfection methods. The WHO and CDC recommend washing at the highest temperature you can. The WHO goes on to say that you can boil or steam combinations of cotton and NWPP. That’s important because that gets you a higher level of disinfection. COVID is somewhat sensitive to heat, so you don’t have to have the highest heat ever to kill COVID. But when you’re talking about a fabric mask that you’re putting over your mouth and reusing, COVID isn’t the only thing that can grow on that or accumulate on it. For some of the bacteria and fungi and spores, I’d like people to at least consider that you might want to periodically be killing off everything that could be growing in your mask and not just COVID. That’s something to keep in the back of your mind when you’re thinking about how you’re washing and cleaning things. When you’re putting things on your face multiple times, detergents become important as well. One of the biggest hazards with laundry in clinical settings is the buildup of detergent residues, which commonly causes skin allergies and irritation. So you want fragrance-free, low-residue detergents.

ETG: We have a question: Couldn’t you just wash the mask with hand soap for 20 seconds like you wash your hands? How is it different?

Songer: When you’re washing your hands, your skin is a fairly impermeable surface; water doesn’t absorb deeply into your skin. As you wash, what you’re mostly doing is rinsing everything off your hands and flushing it down the drain. When you’re dealing with cotton or any multilayer mask, you need to be making sure you’re getting at all the area that’s in those in-between layers and through all the seams and penetrating deeply through all that and anything that’s gathered in the pleats.

ETG: Can you iron polypropylene? Are you worried about that?

Songer: The short answer is you can iron it at the lowest setting on your iron; if you iron at a higher setting, it will melt. I have a Disinfection post on MakerMask where I went through the different temperatures that your iron gets to versus your drier versus your washing machine. The lowest temperature is probably fine, and there’ s a lot of data backing that up. The other caveat there is for the spunbond unwoven polypropylene. If there’s a mixture of other materials in there – polyethylene melts at boiling temperature. So if there’s any of that in the fabric, it’s going to melt and shrink even at the lowest temperature setting on the iron. So make sure it’s 100% polypropylene. The NWPP doesn’t shrink at all at 150F [?]. I tested five different cycles of steaming. With Polyethylene, it shrunk by 20%.

ETG: Could you spray the mask with alcohol spray? Is that going to do anything?

Songer: I vote washing, boiling or steaming. Whenever you start spraying chemicals onto it, you have to be real careful with residues and what you are then inhaling. Those solvents can also break down some materials more quickly. In general, I don’t recommend it.

A lot of people are getting little UV boxes to put their masks in to sterilize them and disinfect them. I don’t recommend that for masks. It’s good for materials that are hard and not porous, but masks have multiple layers. So the known challenge is that UV doesn’t penetrate through all the layers and all the seams. So in general, it’s not recommended because it can’t get to those middle layers.

ETG: You have a ton of this information and more on makermask.org.

Breathability Data

18.  MakerMask Breathability Testing

Photo of MakerMask Designs with Breathability Testing Results

Songer: We’ve got some breathability testing on the webpage for a MakerMask cover which is a single layer of NWPP on top of an N95. We also tested the MakerMask Fit [inaudible:234:24] design and it has breathability showing that for less than five layers of NWPP that works out. Then the data we have showing the NWPP and cotton combinations: I’ve got a picture of a whole bunch of MakerMask Surge designs as well as some of the Craft Passion designs looking at the breathability for three layers of NWPP, three layers of quilting cotton and then combinations of NWPP and cotton. We haven’t managed to get that data published yet, but all of those combinations were breathable. So this reinforces that you can do your two layers of cotton and a layer of NWPP on the outside. The filtration meets the WHO standards with those combinations as well.

Closing Remarks

19.  Thank You

Thank you.

Question and Answer Session

Participants: Dr. Jocelyn Songer, Dr. Elizabeth Townsend Gard, and Joel Sellers

Joel Sellers: We made 25 different combinations. What it really helped with was looking at what was easier to sew. The slippery stuff was all hard to sew, especially when you do it quickly. The two and three layers of polypropylene were tough on the needle. It’s heavy-duty stuff.

Songer: We have a needle recommendation up on the website of 16.

Sellers: I think it may even be an 18. We ordered a bunch of fabric any time we saw polypropylene. Some of them were woven; some were solar.

Songer: A lot of those have UV coatings on them, so that’s another flag.

Sellers: We got a lot of this stuff through Jo-Ann’s, and it had all the information about it. So you’re thinking this may have chemicals that are probably not the best thing.

Songer: Yeah. So a site that often gives that information is SailRite, which I’ve used when I make source materials for outdoor gear. I know that they have one of the lighter-weight polypropylenes. I haven’t ordered from them yet.

Sellers: One of the easiest and least expensive was the Pellon 915. It’s a non-woven, non-iron-on Pellon. It was less than $2 a yard. It sewed very easily; it was very breathable; very comfortable. What I wasn’t sure about was durability. We put some sort of quilting cotton on the inside of all of them except those that wanted just two layers of silk or satin. That was for comfort; I can’t wear that scratchy stuff next to my face.

ETG: Is the thinness a problem? We could put two or three layers of it. Is that better than thickness in terms of polypropylene?

Songer: The thicker stuff tends to hold up better and longer. If you’re putting it through the washing machine, I recommend putting it in lingerie bags. I tend to like to do an outer layer that’s one of the heavier ones, but what the WHO study and guidance show is that one of the nice things about the lighter-weight polypropylenes is that you can layer them and keep the same Q value. They specifically talk about interfacing. The material they’re using is I believe 30 GSM, which has a really high Q value so it’s good for filtration and particle filtration. They added five layers of interfacing at 30 GSM each, so that’s 150 GSM, essentially. It’s still lighter weight than a lot of other materials.

Sellers: Someone thought this was polyester, and many interfacings are, but Pellon 915 is polypropylene.

ETG: We can find out what the GSM of it is.

Songer: That’s something we can test at home, which is really useful in having conversations between sewists and scientists. You can get a kitchen skill which will measure 5 grams or less. So you take your square of fabric and see how much it weighs for a given area – either ounces per yard square or grams per meter square. Then we can at least have one of the parameters the same between us.

ETG: What’s the goal on grams to get to?

Songer: They don’t give you a goal in grams to get to. They were trying to get a certain total particle efficiency. They know from the Q value that you can layer it together and get the same ratio of filtration to breathability. To get 70% particle efficiency, you stack the layers. The more layers you stack, the more filtration you get.

ETG: You could easily do five layers with the Pellon.

Sellers: I can certainly try it. Trying to make the pleats is a little bit tricky when you have lots and lots of layers and it’s very heavy.

Songer: I’ve made a few with five layers of a 40 GSM material. That’s less thick than a shopping bag at three layers, and it is the most breathable mask I’ve tried so I’m really excited. I sent it off to get particle testing done on it. I don’t know if it will make it through five wash cycles and how the properties change over time with washing. We may be able to help solve this together if we can get coordinated so we’re doing the same sort of home experiments and sharing data with each other. There are a lot of us.

Sellers: This one is two layers of shopping bag and one layer of quilting cotton, and it’s really not a problem. It’s fairly easy to wear; it wasn’t bad to sew. Our comment was that our cotton masks are so much prettier, but that’s a minor detail.

Songer: We say it’s a minor detail, but humans are social creatures and we like to have flare and ways to express ourselves. As an engineer, I just want it to be functional; I don’t need it to be beautiful. I can select different colors; what more can you ask for? But my mom gets that extra flare in there with the cloth ties. And if you have a cloth material inside a cotton with a pattern that you like, and you roll it into the nosepiece rather than out, then you get color across the top and the bottom.

Sellers: We made some using silk and chiffon, and as always you’ve got to pin the heck out of them because they’re slippery.

Songer: The only way I could make silk work was hand-sewing it. So I have some that are two layers of NWPP with silk on the inside instead of cotton, which meets the WHO criteria. The silk and NWPP generate their own electricity. I don’t think it’s enough of an effect for it to be meaningful, but in dry conditions it works. It’s soft and comfortable, but I find that the silk is also warm. For me, both the silk and the cotton end up feeling warm because they’re absorbent and trapping that moisture by my face. It feels really nice when I first put it on and it’s cold out and I’m not worried about being active.

Sellers: We did some flannel masks in the winter, which we will never wear down here. The quilted one, I just quilted a couple inexpensive pieces of fabric. But I wasn’t sure why…

Songer: The rationale there is in both commercial masks and the WHO guidance, they ask you to put a nonwoven layer in the middle because it does well for the particle filtration, and that remains true. It’s just you then have a 2-3-inch…

Sellers: There are the two-part patterns with the seam down the center that is more fitted around the face versus the rectangular with the pleats. Does that make a difference?

Songer: The standard that the WHO references, which is the French Standardization Association, they have strong feelings about that. They say you should not have any vertical seams in the middle of it. Because if you’re concerned about all the particles that may or may not be going back and forth, having a seam going straight up through the middle in the center of the mask has holes from the needle. That’s one of the advantages of pleated masks is you don’t have a seam line up the middle. As an outdoors person, I have a lot of experience doing waterproof seams, so it is possible. But if you do have a seam up the middle, you would want to make sure that things aren’t leaking straight through it.

So the quick home test I do – I’m using water-resistant material so that makes it easier – is I go to the sink and I see if there’s water dripping through the seams. That’s not nearly as small as the 0.3 micron particles that higher-level masks get tested with, but that’s the concern there is that you’re losing efficiency by having holes going up the middle. Waterproof seams aren’t well tested yet for facemasks.

ETG: We really want to keep working with you. There’s a ton of people that are asking a thousand questions. Really, the goal is to take all these questions and the samples and think through all these things and put out something that is really made for the sewing community. It’s really important for us to know these things.

Songer: I should have met you at the beginning, too. I’m an engineer, and I’ve done the research and the science. But being able to communicate something as an engineer to other engineers is different than being able to communicate with sewists.

ETG: One more question: These masks seem to protect me a bit more. Am I right about that? I think that’s a good message that we should be getting out there that it isn’t just about…

Songer: It may act as a bit of a barrier. We don’t have the science to prove that it can protect the user. But I designed it with that in mind. I didn’t want bodily fluids to go from one side of the mask to the other side, so that’s why I focused on those water-resistant materials. I was used to thinking about you get blood or spit or anything on a mask that’s an absorbent material, then you end up with it on your face on the other side.

ETG: We have engineers and textile scientists and chemists listening. This is Becky: “I’m an engineer and a sewist and we’ll get the info out. You have got a team behind you that love you and are so excited that you’re here.”

Songer: If we can develop things together, there’s so much we can do to get things tested and make things better. Masks are better than no masks, but that shouldn’t prevent us from continuing to work to be better. For this pandemic, droplet precautions and droplet protection is working, which is awesome. And we see how far we’d have to go from where we are for something that does better at particles. There’s so many things for us to get better at, especially testing. That’s exciting and sometimes daunting and overwhelming.

ETG: This is the beginning of one conversation. We have everybody’s email; we’re going to connect to people. We will work with you. We love you. Thank you so much for your time.

Songer: Thank you, thank you, thank you to everybody who’s been pouring their hearts and souls into making masks and getting them out there. Data now shows that we are making a difference, and as more data comes out hopefully we’ll be able to get better and better.

ETG: Can we put little pieces of polypropylene in all those filter areas and just sew it back up on all the ones we’ve made? I know it’s going to have cotton on the outside, but we’ve just got a lot of these already made with holes in them.

Songer: I’m okay with that.

ETG: We’ve got a lot with filters in the middle, so we’ve got to figure out how to adapt those. And then going forward, we’ll do the polypropylene on the outside and cotton on the inside. But we’ve made hundreds of thousands of these.

Songer: I know. We need numbers on that.

ETG: We’re going to work on that. We will be in touch with you. Thank you! We all love you!

Homemade Mask Guide

At the Completion of the Homemade Mask Summit, the Homemade Mask Guide was created as a collaborative effort between sewists and scientists from JustWannaQuilt.com, MakerMask.org, WeHaveMasks.org, and The Newcomb Institute, Tulane Univeristy. Check it out below:

 Infographic. Title" "Handmade Mask Guide", Information about mask designs using nonwoven polypropylene and the WHO guidance of Fabric Masks. From: JustWannaQuilt.com, MakerMask, WeHaveMasks.org, and the Newcomb Institute at Tulane University

 

Just Wanna Quilt Podcast: COVID-19 Masks with Dr. Songer (June 15, 2020)

Logo: Just Wanna Quilt Podcast Logo

Audio: Just Wanna Quilt Podcast COVID-19 Masks with Dr. Songer (Part 1)
Audio: Just Wanna Quilt Podcast: COVID-19 Masks with Dr. Songer (Part 2)
Transcript: Just Wanna Quilt Podcast Part 1

Transcript: Covid-19 Masks: Dr. Jocelyn Songer of MaskMaker.org joins us – Part 1

June 15, 2020

Transcript edited for brevity/clarity.

Participants: Dr Elizabeth Townsend Gard, Dr. Jocelyn Songer, Whitney, and Alexa

Podcast Introduction

Elizabeth Townsend Gard (ETG), Host: We had a delightful evening with Dr. Jocelyn Songer. She is the founder of MakerMask.org and also a biomedical engineer. She has outdoor experience with backpacking and emergency services and breathing. She has been testing masks and has a strong belief as to what material we should be using for masks. We went for an hour, and then we decided we needed to chat more and chatted for another hour and a half.

So this is part 1 of 2 of a very long, in-depth conversation with Dr. Songer. She is going to be our keynote speaker for our Home-Made Mask Virtual Summit this coming week.

Opening Questions: Dr. Songer’s Background

Dr. Jocelyn Songer (JS): I’m Dr. Jocelyn Songer, and I’m calling from Orange, MA.

ETG: Awesome. We ask everybody this question: Do you have any memory of anyone sewing or quilting in your life? If so, what?

JS: Absolutely. Both my mother and my grandmother sew; my grandmother was a seamstress. She would look after me, and I pestered her forever to let me use the sewing machine, which at eight years old probably was never going to happen. But she did let me use a needle, and she and I did work together to make dolls. She helped me make little patterns, and we would go back to the drawing board a zillion times. But eventually she’d kind of zip one together and then let me do the stitching work. So I have lots of fond memories.

ETG: So what was your life like November, December, six months ago?

JS: Six months ago I was balancing my work on neuromodulation and neuro/biomedical engineering with backpacking.

ETG: Tell us a little more about both. Tell us what that is and a little bit about your path of how you got there.

JS: So my background is biomedical engineering and electrical engineering, and I’ve always been passionate about health and helping other people. I’ve maintained certifications as a first responder. I’m very geeky; I have a very science and engineering mind, so I’ve applied my energies towards developing innovative clinical tools for diagnostics and treatment.

ETG: Very cool. Give us some examples so we can have a concrete understanding.

JS: A lot of the work that I’ve done has been on hearing and balance in the inner ear. So understanding how a hole in your ear can make you lose balance.

ETG: How did you get to that? How did you want to be doing that?

JS: When I was young, I loved health and science. My mom is a nurse, so I was passionate about that. I saw a talk on the brain, and what is cooler than how the brain interfaces with electronics and electrical devices. So that is what nudged me in that direction. Early in my career, I got interested in the ear and the acoustics of sound because cochlear implants was where the brain met electronics the best. Then there were some real-world clinical challenges people were finding where this hearing and balance stuff was interacting. So I studied acoustics of sound and how it’s produced and how you hear it, and that kind of led me into the brain.

ETG: Very interesting. So you’re going along; you’re backpacking; it’s great. Then what happens?

JS: So I am asthmatic, so I have to pay really close attention to when there are respiratory illnesses getting big. I flew to a conference in January and was already concerned about COVID so I had masks that I was bringing with me. I’ve hiked across the US three times now, so I’ve had to have masks with me at all times or to be able to make DIY masks as needed because of forest fire smoke. So hiking across California, New Mexico, Oregon, Washington, Colorado, Montana where there are forest fires 24-7, and you can’t get away from it because you don’t have a house; you don’t have shelter; you don’t have running water. So you have to figure out how you’re going to make traditional and nontraditional solutions come together so you can breathe. For me, breathing is a privilege. Most people don’t think about it very often because they can just do it, but since 2009 I haven’t been able to take breathing for granted.

ETG: Me either. I had a couple of pulmonary embolisms and they didn’t go away. So yeah, not breathing is really awful. If you’ve experienced not breathing, it sucks – gasping trying to get air into your body is not fun.

JS: It changed the whole way I had to interact with the world. I had occupational asthma. I was literally allergic to my job, so my whole life kind of shifted.

ETG: What was your job that was causing that?

JS: I was doing research in a facility that had fuzzy, furry critters, and I became allergic to them over the course of five years. It happens to about 80% of people, and I was from a small subset that went on to develop asthma. But as a vet, I have all this background and real-world experience in particles and what size they are and how they disburse in travel because I wasn’t the one working with the fuzzy, furry critters I was most allergic to but certain sizes of particles travel and distribute more. I had worn an N95 daily for occupational work, so I had some real experience with how they are not always the most fun things to wear or the most comfortable. Similarly, I hiked with N95’s in the desert – reusable ones while I was backpacking. So I watch TV now and I see all these people with masks that are worn improperly just covering the mouth and not the nose, and I’m like: “Oh, I so understand that…”

ETG: It’s too exhausting; it’s awful.

JS: It’s too exhausting, and it can be uncomfortable. So you kind of shift it; in the desert I did that with the smoke because I would be hot and sweaty but I needed something, and it helped. It sort of highlights some of the differences between when you’re wearing a mask for infection control, essentially in a pandemic where the things that you do to treat with forest fire smoke or other things where you’re like, “well, if it’s preventing me from breathing through my mouth, but all that stuff is coming out of your nose…” So every time I see it on TV, I’m like: “if you can’t wear the mask…” The most important thing about a mask is your willingness and ability to wear it when you need to be wearing it. So if it’s an N95 and it isn’t perfect, that’s okay if it’s a mask that you’re willing and able to wear for the amount of time that you need to wear it.

So I feel like some of those human factors are things that don’t get talked about very much. I make my masks, and I know the science really well, which helps. I have experience as a first responder, so I’m used to thinking about these things.

Mask Research

ETG: So we’ve been doing research; we’ve been talking to different people: industrial hygienists and all kinds of other people. We’ve learned about big particles and tiny particles and electrostatic fabric versus cotton and all this stuff that tells us where we’re at.

For those that want to follow along, go to makermask.org.

You’ve got a science-based resource on creating masks. We’re doing a summit next week, and the goal is to gather everything. There’s so much science out there, and we really want to be able to make masks for our friends and family and communities – first responders if they need them again. But there’s too much science out there; it’s chaotic. So tell us about your science. You design water-resistant, non-woven, polypropylene. We just got some polypropylene that’s latex-free and can be machine-washable or disinfected by boiling or autoclaving. So tell us what that is and why that’s important and how you make your masks.

JS: I initially started from the infection control standpoint. What we know most about COVID-19 and the transmission of SARS-COV-2 — which is the virus associated with it – is that it’s mostly transmitted through droplets. There’s a whole long dialog about the different forms of transmission, but for droplets in hospital settings, it means that they wear surgical masks, gloves and gowns. The surgical masks in those cases provide droplet protection, which means they prevent water-based droplets from coming through and those masks are water-resistant. So they’re designed to block bigger particles and especially particles that are in water. That’s why I started looking for water-resistant materials is to block droplets so that you can contain your droplets to you and keep other droplets out.

Polypropylene

ETG: It’s a great website because you’re also suggesting what is polypropylene on there, right?

JS: Yeah. I was used to thinking about polypropylene from backpacking because all of these synthetic fabrics and high-tech materials are really popular there. But most of those materials are woven, so the big stuff goes right through it. The challenge is finding something that’s water-resistant so it provides a barrier to droplets; that’s breathable; and that you can wash, clean, sterilize, disinfect. So you have to have the trifecta there. Reusable grocery bags are nonwoven polypropylene. It’s really hard to talk about because people are like: “I’m not going to put a bag over my head!” Absolutely, don’t put a bag over your head. The key is it’s got to be breathable; if it’s not breathable, don’t use it. That’s rule number one.

It turns out that these reusable, nonwoven polypropylene bags, which I shorten to NWPP, are designed to be touching food, which is good because they meet some standards; they’re designed to be washable so they can be disinfected; and it’s water-resistant because you don’t want the wet stuff from your food soaking into the bag. So it met all those criteria, so that’s how I ended at nonwoven polypropylene from reusable bags. It’s because of that food-grade component that made me select that relative to other things. It feels like fabric, and you can find it in all sorts of sources around the house like with the food grade but in other things like interfacing, which sewists are much more familiar with.   There are lots of variations, but you can get nonwoven polypropylene in interfacing. The caution there is that most of the interfacing that people are used to is fusing interfacing.

ETG: Right, so you want non-fusible?

JS: Right, because fusible has adhesives. Breathing in adhesives is usually bad.

ETG: And stabilizer? They have stabilizer that’s not fusible.

JS: Some of the stabilizer if it’s backing that’s tear-away for some embroidery projects, a lot of that is also nonwoven polypropylene. They’re different weights. I feel like I’ve been down the rabbit hole on nonwoven polypropylene and looking at all the different kinds with different safety and engineering features because when you’re making something, you want to make sure you’re not doing more harm than good.

Whitney: I think that’s why we’re trying to do the summit is because there are so many sewists and quilters out there who want to help and make masks, but there’s so much information and some of it’s conflicting, and it’s like what do we do because we just want to do the best thing.

JS: I want people to wear the masks that they’re going to be comfortable with and that they can get or create. A lot of people have been focused on making a zillion masks and getting them out as quick as possible. As a scientist, engineer and researcher, the thing I can do is take a deep dive on all the science and come at it from the health perspective, too. But there’s so much information that figuring out how to communicate it to people who are sewing masks, wherever they are, more effectively is the thing I struggle with.

ETG examined some nonwoven stabilizer.

JS: The polypropylene in particular that I’m looking for is called spunbond. That gets into the details of how it’s made. But if you look closely at the bags, they have this little pattern to them that looks almost woven.

ETG: This one is flat.

JS: I think what you’ll find is that if you go to tear it, it tears more easily than if you had some of this other stuff.

ETG: This tears really easily. You want it to tear easily, or you don’t?

JS: You don’t want it to tear easily. If it tears easily, it’s not going to hold up as well to washing.

ETG: So for single use, it would be okay. It’s just the washing factor that you’re concerned about, is that right?

JS: Right, the durability. If you’re going to wash it and try to disinfect it to use it multiple times – especially if you’re putting it in the middle layer of a mask, you don’t know how it’s holding up.

ETG: So you just want the basic one that doesn’t have any extra bells and whistles.

JS: Right. If you’re on the webpage, there’s a section called Research Blog. If you page down in there, there’s a place called Big Four: Criteria for Community… That one dives into all of that…

Water Resistance

ETG: Tell me a little bit about the fluid resistant test.

JS: In the US, for something to be called a surgical mask, it has to be fluid resistant. The FDA has really strict conditions for what that means. There’s one specific test that it has to pass which uses synthetic blood. That’s for surgical mask classification. Most of us who are just trying to make masks for community use for friends and family, water resistant is much more easy to check at home to see if it’s going to provide some barrier to water. The simplest version is you just flick water at it and see if it beads up on the surface. If it beads up on the surface, it’s hydrophobic and water resistant, and if it absorbs into it, it’s not; it’s hydrophilic. With the mason jars, you can measure it and quantify it, which makes the scientist in me really happy.

Mask Designs and Layers

ETG: Let’s go back to the masks that you’re making. You have Cover, Surge and Fit. Let’s talk about Surge and Fit because Cover is the N95, and that’s not really where we’re at I don’t think.

JS: Although I’ll mention that WHO has released new guidance on fabric masks. Three layers, including nonwoven polypropylene.

ETG: It’s like they knew you.

JS: One of the things with the Cover is that you could use it over cotton masks if you wanted to have a layer of water resistant over materials that are more water absorbent.

ETG: So, the Surge is the pleaded masks a lot of people have been making. It’s got three layers, and it’s got the pipe cleaner across the top so you can fit it. Do pipe cleaners wash okay?

JS: If you sew them in, they’ve been rewashing fine. It’s on the Surge guidance as two; I find it works better with three because it makes it a little bit stiffer and you get a better fit.

ETG: Three together?

JS: Yeah, I push them together. What I’ve found I love to put in the nose pieces are the ties that go around coffee bags. There are a number of different things you can use to stiffen across the nose as long as it fits.

JS: I forgot to mention that when I wash the ones with pipe cleaners or any other nose bridge, I put them in a lingerie bag because otherwise they get bent a lot.

ETG: So you’re doing three layers and they’re all polypropylene. You’re not doing a cotton layer. How do you feel about cotton?

JS: The nice thing about cotton is everybody has it. For all these other materials, we’ve had challenges sourcing them. Initially, the masks that you could get people wearing as quickly as possible were the best. Cotton tends to be absorbent.

ETG: Which is bad…

JS: I think absorbent is bad for the outer layer of the mask because what I want to do is make sure that I have a water-resistant layer that isn’t going to…

ETG: So one polypropylene layer on the outside.

JS: Yeah, at least one polypropylene layer on the outside. That way if anything with moisture comes at you, it can shed and fall off, and your droplets don’t spread beyond the other side.

ETG: How do you feel about cotton on the inside?

JS: I’m okay with cotton on the inside (against the face). It’s more comfortable for a lot of people because they’re used to it. It absorbs the moisture so it kind of keeps it close to you. If people are worried about the synthetics touching their skin, cotton is good. I still recommend and prefer the nonwoven for all three layers. Part of that gets into the washing and cleaning and drying aspect. Nonwovens dry faster, whether it’s from your own moisture or from washing. It dries really quickly, so that’s less time that you have a warm, moist environment for things to grow in it. So I prefer using different weights of nonwoven polypropylene for the different layers. The default instructions say use three of the same because up until now we haven’t had a lot of variety in where we can get nonwoven polypropylene materials. So if you only have the bags, you can use that for all three. That is not as comfortable as the nonwoven polypropylene in garment bags and other sources. The inner-most layer of the mask for me is mostly about fit and comfort. I rely on those other layers to provide the barrier and filtration and all those other features and factors. I increase the number of layers if I want more particle protection.

ETG: How far do you go?

JS: The very first thing that I did after developing the masks, designing them and proposing them and researching the heck out of them was send them down to ATOR Labs in Florida to get breathability testing done on them. I have been searching for all the other testing ever since. Where I haven’t been able to get professional testing done, I’ve come up with DIY procedures to test all the critical elements. For the professional lab testing, we got ATOR Labs to work with us, and they provided breathability testing: inhalation resistance, exhalation resistance, CO2 accumulation, for all of our mask designs.

ETG: How did it go?

JS: It went well. That was what slowed the initial – I wasn’t willing to put this stuff out there until I had seen that it was at least breathable. We’ve looked at the safety data sheets, and we’ve thought about different potential hazards, and we’re confident that we’re not going to do more harm than good. I tested up to five layers of the NWPP, and they passed the breathability criteria. They also pass the French standard referenced by the WHO. I’ve got some of that data up on the webpage, though I haven’t been able to get it all written up.

Mask Fit

ETG: Tell me about fit because we’ve heard that the fit is really important; if it doesn’t fit right, the percentage of protecting goes down real fast. What are your thoughts about that?

JS: The challenge here is you have to know what it is that you want your mask to do for you. Masks are like shoes: sometimes you wear sandals, sometimes you wear sneakers, and sometimes you wear mountaineering boots. You wear them to do different things, and the same shoe doesn’t fit everybody.

ETG: We saw with the Olson masks and these other masks that are flat, they didn’t fit very well and you had to have the right face and the right mask. So we went back to surgical because we didn’t know who was going to be wearing them. We wanted my husband who has a big head and my daughter who has a small head to both fit.

Filter Pocket? Yes or No

ETG: I’m curious what your thoughts are on the whole filter pocket thing.

JS: That ties into the fit of the mask in terms of acoustics and airflow. Essentially, the air is going to follow the easiest path. So if you have a really good filter in the middle of the mask and it doesn’t go all the way to the edges of it, the air is just going to go out and through the edges. And if it doesn’t fit well on your face, the air is just going to go out the sides or up through the nose around the eyes. The nose piece is super important in that respect because if you don’t have that nose piece, the air is preferentially going to be going in and out through the space by your eyes. Pulling all the air you’re breathing past your eyes is a bad idea for infection control. All these people show these videos of them with a mask on and trying to blow out a candle, and they’re really excited because they can’t blow out the candle with the mask on. I just do a facepalm on that because I can watch the air going out the sides as they breathe because now the air is going through the mask. So if the air isn’t going through the mask, where is it going? What it means is it’s found an easier path out the sides or down the bottom or around the eyes.

ETG: So do the polypropylene ones allow the air to go in and out and not the particles? Is that the idea that it’s keeping the little particles out but the air back and forth in and out?

JS: Right, and the water out. Because the droplets contain the particles, if you’re keeping those droplets out and you have water resistant, you’re keeping the water out but allowing the air to go through. That’s your balancing act. Same thing with particles: Keeping the particles out, allowing the air to go through.

Ear Loops or Head Ties

ETG: You’re using straps and not elastic. We did, too, because it’s a better fit. The elastic was a chaotic mess in our house with big head, little head. But the straps work really well.

JS: and you can individualize straps as well so you can adjust for different head sizes. And elastic stretches, so as your face moves, the mask moves and shifts. Having the ties helps prevent that. The other issue is latex; most elastic you get contains latex. The first reason why we moved away from using elastic was because so many people in healthcare settings have latex allergies.

One of the challenges with all these masks from alternatively-sourced materials is that if you say “cotton” that describes a huge range of things; same thing for polypropylene.

Material Sourcing

ETG: There was a study that came out. They went to Joanne’s and Wal-Mart, which is totally weird. From a sewing point of view, there was not enough specificity for us to really be able to use it. This whole thing with electrostatic, man-made fabric, cotton – how do you feel about all that?

JS: I agree. One of the challenges with all our mask-making efforts regardless of which materials you’re using is standardizing so you know the material you’re using is the same as the neighbor down the street and if the guidance is applicable and useful.

ETG: I was so frustrated with the dataset.

JS: Part of that is because the scientists are doing what everybody else is doing, which is finding the materials they have now available at home.

 

ETG: I felt like there was a discourse disconnect. Why aren’t you asking the sewists? We could tell you. They found a flannel that had a percentage of – it wasn’t a 100% cotton flannel, but we all have 100% cotton flannel. Try to find one that has some percentage of a man-made thing, that’s bad flannel!

JS: As a backpacker, I’ve done a whole bunch of research into fabrics and materials to make my own gear. So I have a stack of all these high-tech fabrics that are ultra-light and water resistant and wind-proof and all these different things. That gets you into the language people use to describe fabrics. That is a real challenge. How do I translate thread count to grams per square meter? I translate everything to GSM because that’s at least a thing I can weigh at home and test and verify where my 400 thread count and your 400 thread count are still…

ETG: The New York Times Article said “batik.” So we bought a bunch of batik and we used it, but we want a little more science in the material for us.

Balancing Material Properties

JS: I think that’s a great dialog to have, though, because the important features are the weave, thread count or fiber density, and the GSM is a weight that at least allows you to normalize things. There are some studies that say denim is great, but they put a little asterisk next to it and say that you can’t breathe through it. But the take-home message is that denim is the best mask material.  But if you can’t breathe through it, it’s useless.

ETG: We had a study come out that said one layer cotton and one layer flannel. So we made these, and we sent them out, and we’re in New Orleans; people are like, “you’re trying to kill us!” There’s no way you can have flannel in the South in the summer.

JS: There’s a scale. If what you’re trying to do is get N95, the best technologies in the world for N95s are coming out of 3M, and most people who have to wear them hate them. They wear them for as short a period as they can because they’re hot, humid, and they’re not comfortable. That’s as good as you can get when you’re pouring a lot of resources into this one thing. But to get an N95 that gives you the particle filtration that’s been the focus of the conversation so that you’re blocking 0.1 micron, it is not very breathable, not very comfortable. Most people are not going to wear it well for more than 10-15 minutes before they pull it down or take it off. As soon as they do that, they’re getting 0% particle filtration. So who’s going to wear it? Where are they going to wear it? And how long are they going to wear it? And what’s the relative risk? For a really high-risk environment, you should wear more layers to give you the best particle filtration you can get. I use three layers of NWPP when I go to the grocery store. I have some that’s thicker that gives me a higher degree of protection, but I don’t want to wear that very long. When I go hiking or into the Maker Space that I’ve been helping out, I wear something that’s a little bit more breathable because I can wear that for four hours straight without taking it off and without touching it to readjust it.

ETG: There’s a whole list with chiffon silk, 100% polyester… What are we supposed to do with that? Do we add two layers outside, inside? Are we really spending $40 a yard on 100% silk? Is that better than polyester silk?

JS: It is very different, certainly. When you’re mixing and matching fabrics, the first thing I would say is to make sure that the washing instructions are going to work for all of them. Also, in terms of how it wears out, you that sew a lot, you know along the seams if you sew your chiffon to your canvas denim…

 

ETG: It’s going to pull out if you’re not careful. The weight differential is going to mess it up.

JS: When people are going down these rabbit holes on chiffon versus silk and not giving us any information about which of those materials they’re specifically talking about, a lot of that is thinking about that really fine filtration.

Electrostatic Filtration

EGT: They’re trying to do the electrostatic for the teeny-tiny drops. That’s how you keep them from getting in.

JS: That’s how you get better particle filtration while still keeping breathability.

ETG: And how do you feel about that?

JS: I feel like it’s a challenging thing that’s still very experimental. For me, it worked well because NWPP holds a charge very well like other synthetics. A study that just came out June 2 is like yay, not only do you have your filtration for lower weight and more breathable materials – 43 GSM interfacing in particular – I think that’s kind of light weight. It doesn’t hold up as well. The WHO guidance specifically says non-woven polypropylene interfacing is a good material to use. That’s based on this paper I was just mentioning which shows the particle filtration, and they show that hydrophobic materials are able to store a charge on them which cotton can’t, and unlike other materials like silk, they keep charge for a longer time. It holds a charge overnight at room temperature. They tested it at body temperature and high humidity and found that it held a charge for at least an hour, which is pretty good. That’s where the guidance for using synthetic layers like nonwoven polypropylene and polyester are coming from. If you roll them between your latex gloves and build up a charge and you do that for 30 seconds, it builds up a charge that can last an hour even in humid conditions to give you a bit of a boost on the filtration. That’s interesting and exciting. We’ll take extra boosts if we can get them. It’s specific for hydrophobic materials because if it absorbs water, it doesn’t keep the static charge.

We don’t know how that kind of treatment is going to impact the durability for reusable masks. If you’re sitting there and rubbing the heck out of it for 30 seconds every time you wear it, that’s going to break it down faster. So like many other things, there’s a trade-off there. I’m curious to see how that pans out over time.

ETG: So on Amazon we’re looking for: non-woven interfacing polypropylene, breathable, dust-proof, anti-fog. Then it’s got one that’s waterproof and one that’s not.

JS: So waterproof and breathable don’t tend to go well together. When I think waterproof, I think Saran wrap. It’s waterproof; it does a great job at blocking particles; but don’t put it over your face; it is not breathable. The most important feature of your mask is that it’s breathable and not hazardous.

Burnout

ETG: People have made a ton of cotton masks; most shops are selling those, too. We may not be making them in the crazy way we were; it got political; companies are making them; people think they don’t need to wear them. I don’t feel that way.

JS: And also burnout. I just want to say to all the people who have been sewing hundreds, thousands, no matter how many, I have seen the most heartening thing while the whole world is falling into chaos for so many reasons. I agree that spending 103 hours a week on masks for months at a time isn’t sustainable.

ETG: It was really exhausting. So going forward, polypropylene is going to be hard for people to get, I imagine. What are your thoughts about a layer or two layers of polypropylene plus cotton plus chiffon. If people are out there freaking out because they have all this cotton but no polypropylene, what do we say?

JS: I would say that the best mask is a mask that you can have, you can get, you can make. So I don’t think we should throw out these other masks. We know the science is evolving rapidly around us. For a long time, my thought is if you have some nonwoven polypropylene, if you can just make a layer of it to wear over cotton masks so you get that water-resistant, hydrophobic layer on the outside…

Mask Layering Combinations

ETG: So the outside is key. You wouldn’t want cotton and then polypropylene; you want the polypropylene on the outside?

JS: I want the polypropylene on the outside, absolutely. I think two layers of cotton inside, one polypropylene outside or one cotton, two nonwoven polypropylene; all those are fine. I would advise against the cotton sandwich where you have a water-resistant, non-woven polypropylene with cotton or some other absorbent material in the middle and then NWPP on the other side because of washing and disinfection. If you’re trying to wash something, and you trap all this warm gunky stuff in the middle, how do you make sure that is getting clean when you have two water-resistant layers on the outside? That may be fine for a disposable mask, but for anything reusable, that’s the sort of thing that absolutely needs validated disinfection and cleaning methods because that scares me in terms of what might grow in the middle.

ETG: Can you do the opposite with cotton on the outside but the polypropylene on the inside?

JS: I think that’s okay. I wouldn’t consider it ideal because anything coming from the outside is going to get trapped in that absorbent layer, and you’re holding it closer to the face. That’s the thing that I dislike about that. But you do still have that water-resistant layer in the middle that’s acting as a barrier to hopefully help keep things from going out or going in. But I have to note that the WHO and the CDC and all the guidance out there right now says that you should be using masks for source control. The only thing you’re concerned about is keeping your germs from going out.

ETG: That’s any cotton mask, then, on that level is okay.

JS: Yeah. Some of them are going to be better than others. That’s why they all say use multiple layers because one layer acts as a diffuser potentially; that gets into a longer discussion. But for what the government and regulatory officials say we should be doing, having just that nonwoven layer in the middle serves that purpose; it helps keep your droplets to you and the other droplets going the other way. If you have an absorbent layer on the outside catching everything that’s being thrown at you, and then it’s drying out, once it’s dried out it’s a smaller particle size. So I don’t recommend having an absorbent layer on the outside. There isn’t any science that I’m aware of yet that backs up my intuition and my view and analysis of why that’s concerning.

ETG: You think three layers of NWPP is the best, but if you have the masks that don’t have that, it’s okay; it’s better than nothing. And if you’re trying to do a hybrid, that’s not super key.

JS: Pretty much. I will say that in terms of what that layer is closest to the skin, I’m not sure. Having that be cotton like the WHO recommends may be just as good as having it be all three NWPP. I find it less comfortable and too warm. There are a lot of reasons why I recommend that three layer. Part of it gets into washing and disinfection.

Washing & Disinfection

JS: There’s a whole blog post that goes into way more scientific detail on that. If you have a mixture of materials and fabrics, especially the absorbent ones, when you wash them with detergent you can get skin irritation.

ETG: You have to use detergents that support allergy return. Fragrance free.

JS: The EPA has a whole site that goes into detail. But if you’re going to use detergents, keep that in mind because you’re holding things up against your face for a long period of time in hot, moist environments.

Transcript of Just Wanna Quilt Podcast Part 2

Transcript: Covid-19 Masks: Dr. Jocelyn Songer of MaskMaker.org joins us – Part 2

June 15, 2020

Transcript

Transcript edited for brevity/clarity.

Participants: Dr Elizabeth Townsend Gard, Dr. Jocelyn Songer, Whitney, and Alexa

Elizabeth Townsend Gard, Host: Let’s start with you and what you really want quilters to know as a scientists coming into this as someone who cares and has breathing issues yourself. What should we understand?

Dr. Jocelyn Songer: I think the first thing is how much we appreciate you, because all of these efforts to get masks to as many people as we can as quickly as we can would not be happening without you.

Second is that even though it’s complicated, it’s worthwhile. Keeping breathability in mind is always an important thing because we’re covering the mouth and nose. We want to do that as safely as we can. So it has to be breathable, and it has to be something that people are willing to wear for the entire time they need to be wearing it.

In terms of the science, ask questions. As long as you keep asking questions, it will force people to come up with better answers. We’re all in this together. We’re all working to create better solutions to make our families, friends, community and healthcare providers safer. We’re doing an amazing job at that even if things may not be perfect yet. Don’t let perfect be the enemy of the good.

Alexa Magyari, Host:

We’ve made all these masks. You’ve proposed a couple solutions in Part 1; one if to make a nonwoven polypropylene cover to go over a cotton mask that we’ve made. You’re suggesting that this is superior to making nonwoven poly propylene (NWPP) filters to put in the filter slot?

JS: I would say yes.

AM: Would you say that making those filters is better than nothing?

JS: Yes.

AM: Do you have any other insights into how to modify these cotton masks that we’ve already made to improve them?

JS: What I would do is if you can put one layer of NWPP and have that go over it, that will give you that extra water-resistant boost. A lot of NWPP is pretty lightweight, and one of the advantages is that it’s really breathable. So you can put a layer of it over an N95. N95’s are not the most breathable or comfortable things in the world, and it’s still breathable. We tested that, and it got a big thumbs up.

AM: So we know how we’re going to fix our imperfect masks of the past if we’re so inclined. Moving forward, the gold standard in your opinion is the three-layer NWPP. In an ideal scenario, where are we sourcing that material?

JS: That is the big challenge. The ideal material in an ideal world is medical-grade spunbond nonwoven polypropylene. There isn’t a great, easily-accessible source for that yet. We’ve got people working on that and trying to coordinate with distributors. But moving forward, that’s what we would like to do is to make it so that as this continues, there’s a place that we can point to where mask makers can obtain materials that we’ve tested and know are great.

AM: In the absence of being able to buy it in bulk, is the best thing to do to cut up my bags? Or is it better to start with the interfacing?

JS: I haven’t been using the interfacing, so I can’t personally attest to how well that works. But if it’s a separate layer, you can test that out on your own; see if it’s water resistant; see how it holds up as it gets washed. I recommend boiling or steaming to disinfect.

The reason why I suggested the reusable grocery bags if they’re unused is because if they’re designed to be touching food, that gives you an extra level of safety because those are food-grade material while other materials may not be. So if I could get it, I would go medical grade; if I can’t, food-grade is the next best. From there, I use conference bags because they’re designed to be the same structure as far as fiber density and tensile strength and weight in GSM, they’re very similar. If you’re using interfacing, you just have to make sure it’s not diffusing interfacing and that it’s free of adhesives. A lot of those adhesives are latex-based. Latex allergies and sensitivities develop over time, so the more exposure you have to them, the more likely you are to develop allergies. So breathing that in constantly close to your face…

ETG: Could create a latex allergy even if you didn’t have one because latex is not something you’re supposed to be breathing through. Is that what you’re saying?

JS: That’s what I’m saying. In general, we know there are so many bad things about inhaling adhesives. I’ll look into the latex bit a bit more, but that would be really problematic.

ETG: We had gotten into learning about H600. I think on your site somewhere you say don’t use that.

JS: Halyard H600 is not just spunbond NWPP; it also includes melt-blown NWPP. So that changes your risk profile. It’s really commonly used in clinical settings, so people have a lot of access to it. I haven’t seen breathability data on it yet. I have made some masks out of it with a single layer, and it’s a little hot and humid for my liking.

ETG: So it’s the breathability you’re worried about rather than safety. It seems like the company is freaking out a little bit that suddenly their surgical wrap is being used for a mask.

JS: There are a whole bunch of potential reasons for that, and I don’t have all the answers. I do know that for melt-blown in general when you cut it, it leaches smaller particles into the air. The particle size from the melt-blown is a size that’s really bad to inhale.

ETG: So stay away from those because we just don’t know, and they’re hard to get, anyway. We’ve tried.

JS: It’s hard to get, and in order to get improved performance on the water resistance especially, they often use surface treatments and coatings. Some of those are things you really don’t want to be inhaling. I have no data about whether or not the Halyard H600 uses that. That’s the challenge when you’re dealing with alternatively-sourced materials. You’re using things outside of the normal scope. Before I recommend things, I try to do a hazard analysis to try to determine all the safety concerns. So it’s a cautious world of more good than harm. One of the advantages of cotton is we’re very familiar it; we’ve been using it for over a hundred years; we’re not scared of it. So there are some real benefits to that.

For that spunbond NWPP, I recommend washing it first so you get anything from the manufacturing processes rinsed out at the very least. I’ve done a ton of research into the backgrounds and risks for the materials and the safety data sheets when you can find them. Mostly, you want to find stuff that hasn’t been coated and doesn’t have extra treatments; it’s breathable; it’s going to stand up to whatever your washing/cleaning/disinfection procedures are and that has water resistance and some filtration. Most of the data that’s coming out is on the water resistance of something that you can test at home by flicking water at it. There are all sorts of ways. The cough syrup cups that they give you are a teaspoon of water, which is 5ml. Just put it over a jar, pour the water on, and see if it goes through in 60 seconds. You can make that quantitative, which is nice.

For breathability, I have a DIY at home test for that as well. Some people pick it up, put it to their mouth and breathe through it, but for materials I’m not sure about, I hate the idea of putting it up to your mouth and trying to breathe through it. So I use a toilet paper tube; take an elastic band; put the material over the end; then blow a lint ball or a piece of cotton ball with it and see how far it goes. If you can’t move that lint ball, it’s not breathable.

ETG: That’s such an important component of it. So on Amazon, when I look at the sheets of polypropylene, it’s very confusing. I don’t feel totally comfortable with it. Then I went to the reusable grocery bags. How have you been finding your bags?

JS: My mom found these for me, so I’d have to ask her strategy. I know that we’ve gotten a lot of bags donated from all these conferences that have been cancelled and from grocery stores that aren’t allowed to use them right now. The savings bank in our town had several of them that they were willing and able to donate. Being able to get them on Amazon is a new thing for the past few months. As soon as people realized that they could be used for masks, they were impossible to get.

ETG: There’s a lot of nylon ones, and that’s not what you want.

JS: Right. I can look after we get off the call and see if I can find some search parameters that will help with that. We’re working with some companies to try to get more consistent materials out there more easily. It’s a pain to break down bags and cut them up into masks instead of getting it by the yard.

ETG: That would be the most ideal. I was looking at wholesale companies because you can probably go there and get stuff and just not put the logo on it. I went to one and it said 80 GSM nonwoven polypropylene. What GSM are we looking for?

JS: 80 is good for the outer layer. One of the advantages of using something that’s 70 or 80 GSM is that the melting point tends to be a little bit higher. Sometimes lower weights are made differently, so they don’t hold up quite as well. That’s been one of the challenges with some of the crafting materials is that they don’t hold up to the boiling and sterilization techniques. Most of what that tells me is that they probably have polyethylene in them, which shrinks a lot because it melts at boiling temperature instead of 100C higher.

ETG: Tell us about the thickness and GSM. Are there other thicknesses we should be looking at?

JS: I look for 60 to 80 GSM because that gives you pretty consistent properties throughout – mostly 80. If I can get it, I go for food grade and stuff that’s designed to be reusable. There’s been some challenges with olefin, which you can sometimes get by the yard. I haven’t gotten any. But the melting point of it is more like plastic.

AM: What is the set of masks that in your opinion are harmful? We’ve talked about non-breathable masks and the harm in that. You briefly mentioned single-layer masks as potentially harmful. If you could talk a little more about that and then maybe add whatever else to the list.

JS: I definitely have a Do Not Use list:

  • Anything that might have fiberglass in it; vacuum cleaner bags because they aren’t breathable. That comes up more than you would think. People think they just need to get the particle filtration to be protected; they don’t try walking up the stairs with it. So anything that you can’t wear for 15 minutes is not going to work.
  • Adhesives, latex, materials with coatings. That comes up a lot with metal-infused materials, which may have antiviral properties although frequently they haven’t been tested for that. That’s hard to do with a DIY home test. That’s often achieved with coatings, which are maybe okay to touch your skin; but just because you can have something contacting your skin, that doesn’t mean you should be breathing it in.
  • The other consideration is reusability, which means you have to have a way to clean them and you need to know that all the layers are getting cleaned. That part of the conversation I think often gets ignored because it’s not as cool as talking about the particle filtration. But can you clean it effectively?
  • So that leads you into bleach, which both the CDC and the WHO say is an okay thing to clean your mask with. All the little caution flags should be going up because you are putting it over your mouth. So if you do use bleach, which I don’t recommend, make sure you rinse it, rinse it, rinse it. One of the challenges with laundering is that if you don’t get even rinsing you can end up with more bleach concentrations than you anticipate. Though you can smell it at levels where it is well below being hazardous, most of us don’t have a good way to tell where on that spectrum things are. I don’t have a DIY test for that yet, so I say no bleach.

For disinfection, boiling works.

Microwaving is not a great idea because the nosepiece usually has metal in it, and you don’t want to put things with metal in the microwave.

AM: How long should you boil it for?

JS: I recommend ten minutes. WHO recommends one minute. That is assuming that the mask is submerged in the water the whole time you’re bringing it up to temperature; you’re boiling it for a minute; then you’re letting it cool down all the way back to room temperature in that same pot of water. If you do that, then one minute may be okay. There are a lot of variables in that. How hot is it outside? How long does it take to cool down? You’re leaving your mask inside the pot of water for this long period of time and it lends itself to forgetting about the mask in the pot of water. Then you’re leaving it sitting in a warm vat of water for some unknown amount of time, which is problematic.

So I recommend just boiling it for ten minutes and then hanging it to dry. Then you know it’s been at that temperature for a minimum amount of time, especially with masks with pleats or seams; you have multiple layers and you want to make sure that you actually get that heat level consistent throughout the entire thing to maximize disinfection.

AM: Can you give us a laymen version of why one layer is harmful?

JS: I wouldn’t say that it is harmful; I would say that it is less good, which I guess is a hedge. With one layer, you don’t get as much of a barrier, and if there are inconsistencies in the material, if there’s a needle hole through it, or there’s a seam down the middle, with a single layer it increases the odds of things just going through the seams. If there’s a little bit of damage, then that’s a failure point. Two layers reduces the risk of any individual imperfection giving you a straight route out.

AM: So it would act as a diffuser.

JS: Yes.

AM: That’s why I was asking that question. If you’re only wearing one layer, it could spread the germs out more?

JS: Not as far in front of you but maybe in a broader area in the meantime. It does depend on the kind of material. That would be my concern with a single layer; it goes to both of those.

AM: But a single layer is better than none.

JS: Yes.

ETG: Can you help us understand that study that came out with the cotton and chiffon? You guys keep chatting while I pull that up.

AM: I come from a school of public health where I was a PhD student. I came into this problem as the person that was putting all the hospital requests together so that people were donating through sanctioned channels. My big concern as someone that is worried about liability is we want to make sure that the masks are going to the administrators who can make sure they’re being used in a clinically-appropriate way. My next set of questions is about how we can start educating healthcare facilities about these masks.

Have you done that? Have you had a good response from healthcare facilities? Do you have any ideas about how we can continue to do that?

JS: Yes, I’ve been working on that and I have some ideas. One of the things I’ve been doing is keeping up with the regulatory side of things: the FDA guidance, emergency use authorizations, the triaging of supplies there, the risk alternate profiles and all of that.

That’s a challenging one. Most people don’t want to spend a lot of time looking into the regulatory side of things, but a lot of the requirements are put there to help ensure safety – especially as we get into these other, bigger issues.

So for mask makers, an important thing is the labeling; making sure that what is in the masks is known by whoever is using them, especially in healthcare contexts. We’ve talked about latex allergies already. It’s just such a big one that people aren’t used to thinking about. So having the appropriate labeling with what materials are actually in the mask is really important. And then the cleaning and disinfection instructions are required by those FDA labeling requirements. They pretty much apply to people whether they are manufacturers like Old Navy or somebody in their home making masks for their local hospital.

We talked a little bit before about knowing what the mask is designed for and what it’s going to be used for. Clarifying that is going to be important for the general public and also for healthcare facilities. A lot of the masks they need are for patients coming in the door. The requirements for what that mask needs to be are very different than what the requirements need to be if you are going to be in an operating room. And right now, the guidance and things that hospitals are looking for in masks is based on surgical masks, which can withstand synthetic blood at high pressures, and respirators, which are for airborne contaminants. Figuring out how these new classes of masks fit into that is a challenge and has been one of the things that hospitals, administrators and mask makers are all trying to address.

AM: The hospitals are asking for multilayer cotton masks almost exclusively. I think there is an opportunity to educate them about the work that you’re doing and the up and coming science and see if they have preferences for these masks taking into account the differences. I would love to move forward and think about how we can do that in case we have another round.

JS: I think you’re right there. A lot of how the adoption has been going is hospital by hospital. I know in our area we have a number of hospitals that wanted to use the MakerMask designs with the NWPP. We’ve gotten a sense of how we want to wash and disinfect them and for what the requirements and rules are. In general in hospital settings, reusable masks have not been the standard because if you’re reusing a mask you need to be able to disinfect it or sterilize it. And in hospital settings, those words mean very specific things. You actually need both cleaning and disinfection and you need to demonstrate that you are getting the level of disinfection you need. In most of the hospital context, most of the masks being made – cotton or otherwise – is a scary thing because it’s not going through the normal processes. So making masks that can be disinfected and sterilized or autoclaved is important. But it’s not the way they’re used to processing things.

So with cotton, a lot of that is going into the laundering facilities that are off site in many cases. And those processes rely on bleach for disinfection. So that gets me back into whether we’ve actually performed a hazard analysis for the way they’re doing that kind of batch processing of things because most of the things you put through the laundry aren’t things that you’re going to be breathing in.

ETG: We got a recent request from our local library wanting to give out masks to people who come into the library. These kinds of requests come in all the time, and I don’t know – when you think about kids and adults and all kinds of people that are going to come in, I don’t know what the answer is.

JS: I think these are user cases where people with public health expertise really come in handy because one of the things that we really need is a massive public outreach and education campaign on how do you use a mask; how do you wear it correctly; how do you put it on; how do you take it off. Why is it that it’s not okay to pull it down below your nose? Every night on the news I see all these people with masks, and I’m going oh, no. It’s because it’s a new thing for people, so they don’t know that they need to adjust the nose bridge down and that every time they touch the front of their mask and move it around, anything that’s on their mask is now on their hands, and anything that’s on their hands is now on their face, and that’s not good. That goes back into your question about what should the library be using. What people in the library should be using is what people in the grocery store should be using, which is what the general public when they go into enclosed places should be using. That is the thing that the argument rages on. What the CDC recommends is not the same thing as what the WHO recommends is not the same as what I recommend. There’s still so much variation out there that it’s a struggle for everybody.

ETG: This is the American Chemical Society nano-study that was looking at the different layers of fabric. This is the one that’s getting all the attention that was published April 24.

JS: The WHO guidance references a new ACS nano-paper. That’s the one that’s all about the NWPP which was published June 2. It’s been accepted and is available but not in the finished format.

ETG: This one is looking at filtration where you’re looking at breathability and protection. Filtration comes into yours because the polypropylene is what is keeping things out, but they weren’t looking at breathability necessarily; they were looking at…

JS: Pressure differential is their measure of breathability.

ETG: So when you look at this, what do you see?

JS: N95 do well at 99% filter efficiency, and the pressure drop is really small, which is good. As you go up, the pressure drop is a little bit higher though relatively close. If you use a cotton quilt, they’re saying it works okay for…

ETG: This is the weirdest part: They’re saying a cotton quilt is cotton batting and cotton. I’m not sure how that pressure differential is 2.5 when you’re literally breathing a quilt in. That’s bizarre to me.

JS: It is a bit bizarre. One of the combinations that I tested early on I didn’t use a cotton quilt; I used polyester batting with a layer of NWPP on either side. It worked okay in terms of filtration. I know when I was in the desert and the forest and the smoke from the fires was nearly choking me, one of the things I tried was taking my filtered jacket up over my mouth to try to block the air that way. It filters reasonably well, and I’m surprised that their pressure difference was as good as it is.

ETG: They said the way the cotton is put together it’s got a poly urethane scrim, and that’s why it was okay. But they weren’t using polyester batting; they were using cotton batting that had a scrim.

JS: In general, it works. The challenge there is that it is so hot. This is one of those things that gets into the CO2 accumulation and diffusion, which is another can of worms. If you have a loose-fitting mask, it doesn’t matter as much; if you have an N95 cell mask with a really good fit, that batting cracks the air into this weird buffer and you get carbon dioxide diffusing and accumulation, which you don’t get if you’re just using cotton. So quilting I would still say is bad for a lot of reasons.

ETG: The other one that seemed really promising was the cotton/chiffon, and that’s gotten a lot of attention. They gave us a list of what chiffon they used, which we can replicate.

JS: I haven’t done a deeper dive into chiffons. I would have to look at that more closely.

ETG: They did give us the number, so you can look it up at Jo-Ann’s store.

JS: That’s really convenient.

Don’t use anything with spandex. The stretchy materials are bad. I guess that would be my challenge with chiffon. As you pull it tight to get a good fit, it increases the pore size – the gaps and the holes – and your filtration isn’t as good. I’d have to look again at the details.

I’ve been so sucked into the paper that just came out with the WHO guidance talking about the three layers. It’s on the MakerMask website under the Research Blog. I did a quick summary of the findings.

ETG: You must have been thrilled about this study that it really confirms what you were saying about the polypropylene.

JS: I was excited to see somebody say polypropylene in their out-loud voice, yes.

ETG: “Multilayer polypropylene material is superior or at least comparable to materials used in some medical facemasks.” Amazing. Well, I’ve already ordered some bags off Amazon, so we’ll see how that goes.

JS: Being able to have the number for Jo-Ann’s Fabric for the material you can actually get which is the exact thing is just so helpful.

ETG: They did not do that with the cotton, though. They did the same thing with flannel. They got flannel from Wal-Mart, and I can’t find it. They didn’t say what the number was, just that it was from a Wal-Mart superstore. That to me just seemed a little unscientific.

JS: That is a really interesting thing watching all the studies come out about the materials is they’re not as scientific. There’s a gap between a lot of the testing that’s being done and the real-world scenarios.

ETG: I just wanted them to be a little bit more precise.

JS: That seems reasonable to me.

ETG: What their lack of specificity does is makes me doubt their conclusions. That’s the problem I have with it. Because the little bit that I know, they didn’t get right, it makes me not trust the science.

JS: I think that’s a real challenge. They provide information on the porosity, which is good, and the thread diameter. That doesn’t translate to things we can check or verify at home and when we’re trying to source materials. I also call it the apples and oranges problem because everybody measures it slightly different ways and providing different numbers. At least for this, they provided new information on N95’s which they gathered as well. So there’s some formalization. It doesn’t translate the information into something that’s usable by you to figure out how to replicate it. How do you replicate it? How does disinfection and cleaning work? Did they get the same numbers? Can they be cleaned? That’s another big can of worms because the science is so new for that. Before, you were talking about where things were in November. Where was all the data and research for homemade masks in November? The answer was there were very few studies. The materials were even less well specified than we’re seeing in these new studies. In November, most of the science for DIY masks was 100 years old.

ETG: Who’s going to make a mask out of a tea towel? As a quilter, we’re not going out to get tea towel fabric. So there was an interesting disconnect really early on.

JS: And that disconnect makes a lot more sense when you think about it in terms of a lot of those masks were being used for air pollution and smoke, which is not the same as infection control. Nylon may give you a great fit, but how do you take those nylons off in terms of infection control? It’s stretchy, so you’re getting anything that’s on that mask all over you, and then you’re pulling it up over your face, past your eyes, over your hair, so anything that was on the outside of that mask is now on the inside as you pull it up and off over your head; or you have to put your hands in it to pull it up and off. How do you do that without getting anything that’s on that mask all over your hands and your face. I’m just going to say that for COVID, I have problems with using the nylon on the outside. For airborne stuff that you need an N95 for, I think it’s great. If I have some reusable masks for air pollution and smoke, the nylon solution seems fine. But I do not recommend that for COVID.

ETG: I think the science will get more clear. But there’s kind of this weird moment of people almost like: Oh, we’re done with this. There’s a sense of: We’ve moved on.

Masks for Kids/School

What do you think? Do you think we should still be making masks and getting ready for the fall? What are your thoughts as people come back to school? There’s a lot going on at the moment, and I’m curious where masks fit in.

JS: I think that right now is a good time for us to be recollecting and having these conversations and thinking about next steps while we kind of stop and take a breath. Try to spread knowledge about how to wear masks correctly. Try to get that to be pervasive. As we hit summer, I think we’re actually going to see another bump in demand because the masks that we’ve been using in the colder months are not as usable now when it’s really hot. Think about how we’re going to adapt to have masks that provide the best protection we can that we can actually wear while we’re out doing the things we do in the hotter months.

Our target should be to make sure that whatever mask people have on, they’re willing and able to wear it for the amount of time that they are out and about in high-risk areas.

Think about how we make asks for kids and what safe combinations for kids are.

ETG: What do you think that is?

JS: That is a good question. Everything is a little bit riskier with kids because they’re smaller. It’s scarier to be in the unknown there. We’ve been making masks for the kids, and we do scaled down versions of the MakerMasks Surge – the pleated masks. We’ve been doing them with two layers of NWPP. In general, I’m erring on the side of decreasing by one layer.

ETG: Because why?

JS: Because their lung capacities aren’t as big. They’re not exchanging as much air as forcefully as adults. There’s some data that you can break down the age ranges for, but that’s the reason. Kids are not just miniature adults. I used to teach CPR for kids and adults, and the breath size that you use if you’re doing respirations is different. Lung volumes are different, and the force at which everything happens is different. So I want to make sure that kids are something that’s really breathable.

What are the reasons that people take masks off or pull them down so they’re just covering their mouth and not their mouth and their nose?

There are usually two reasons:

  1. It’s not very breathable;
  2. It’s getting too hot and it feels kind of claustrophobic.

Both of those things happen when the mask isn’t breathable enough.

So I definitely think you’re way better off doing two layers and wearing it for the entire hour you’re out – and this is true whether you’re an adult or a kid – than having the best filter in the world that you’re only willing to wear for 15 minutes.

ETG: So putting cotton or something that’s comfortable on the inside is completely fine, but having the outside be polypropylene.

JS: That’s what I would do. Just as a reminder, the CDC says no masks for kids under two. Some other countries say no masks for kids under three. I would keep that in mind for young children or anybody who can’t take the mask off unassisted; they shouldn’t be wearing a mask.

For kids that have sensory issues, I do recommend that inner-most layer have a pair of pajamas or anything they love that’s comfortable that they’re willing to have touch their skin. Depending on  age, I would make sure they have two masks. We make matching masks for their dolls.

ETG: Can we throw them in the wash? Are they not getting clean enough that way? You did say that you were washing them in a lingerie bag.

JS: I put them in the lingerie bag so the nosepiece doesn’t get deformed. Be careful with the detergents you use, and use the hottest temperature that’s reasonable. The NWPP I hang dry.

ETG: Do you think that would be okay even if you had a cotton side of it?

JS: Yes. It takes longer to dry with the cotton.

ETG: But you’re okay with washing it in hot water and letting it hang dry.

JS: Yes. And if you don’t want to hang dry, tumble dry low.

ETG: I feel like I have some direction. I ordered the bags, and we also have some polypropylene that we got that’s very thin. I’m not sure what that is, but maybe I can putt that between. I’m going to make three layers, two layers, and two layers with cotton so that we’ll have those to test and see how people feel about them.

JS: When I go out hiking, I use a two-layer NWPP.

ETG: Because it’s too thick when you’re really exerting, and you’re not in the middle of people.

JS: Right. For me it’s a low-risk environment. I stay at least six feet away from everyone as much as possible, and it’s an outdoor space so the risk parameters are different. In the grocery store, I want a three-layer one. I’m also used to using masks, and that makes a difference because it isn’t the same. No matter how good a mask is, it’s still different. I have to remind myself when I first put it on to breath easy for a few breaths to get used to it again and not to run up the stairs right away.

ETG: I did housework in a mask just to get used to it and determine at what point does it seem impossible. Just get used to how it is.

JS: That’s the thing I haven’t heard other people talk about, either, is practice. Whenever you’re using a new tool, it takes practice. Facemasks are medical equipment.

ETG: I know everyone is going to be beyond excited to hear this because really, you are who we’ve been looking for. I feel like I have direction, which I really didn’t before.

AM: I’m a health economist and not a science person. I read all the studies and was trying to do the best approximation of what was in the study, but it was a very poor substitute. I didn’t feel like I could replicate it with any confidence. So I think this was really great to have a scientist that actually understands the materials we can get, because that’s a big deal.

JS: And this is a hard problem. If there was one set of best practices everyone could follow, we’d be doing it and it wouldn’t be as hard. It’s hard for everybody to be sorting through all this. We expect the higher-up people to be saying yes, this is what everybody should be doing. We thought we were going to get that in March, then in April, then in June. The world is still converging on best practices, and I think we’re all getting better as we go. That part is exciting.

ETG: It’s been a really interesting intersection of science and sewing that was unexpected.

JS: And DIY efforts.

ETG: You’ve spent some nice, quality time with your mom, I’d imagine.

JS: And she’s way better at sewing than I am, and we have one machine. She’s always telling me I run the sewing machine with a lead foot. Slow it down, and it’ll come out straighter.

Whitney Chatmon, Host:

When all these studies about masks are coming out, and scientific articles in general, how do you go about analyzing the research and what do you assess when you’re looking through all of it?

JS: That is a really good question and probably a whole course.

WC: I found myself recently reading some research, and I was – I haven’t taken science since I was a freshman in college.

JS: I first check to see if they’re original research and if they’ve been peer reviewed because that makes a big difference. A lot of the stuff that’s coming out is meta-analysis, which is stretching back for three decades. I read all those older papers at the beginning, and I’m curious to see what the new ones are. I would look to see if they have error bars; if they have more than one sample. A lot of them are using the same word: particle filtration. Particle filtration means about a thousand different things depending on who’s saying it. I look to see if the method they’re using is the same as anything else and anywhere else because if I can’t compare it to other things, it’s not super helpful.

WC: I was wondering given your personal history with respiratory illness, how did you view the current pandemic when it was starting and the progression of it?

JS: I think it meant that I was cautious earlier. I actually went to Las Vegas for a conference in January, and I knew I was going to be backpacking for a week in the desert afterwards without having any contact with what was going on. So I went to that prepared. I had my masks with me. I wear a mask when I fly all the time, anyway, because otherwise, seven days after getting off the plane, I would get a new respiratory illness.

Then because of my previous respiratory history, I have almost every able commercial reusable mask that was in existence before, as well as disposable masks. So I had a full set of them to be able to compare and a lot of experience with what I liked and disliked and absolutely abhorred in masks. So that gave me some context to be thinking about it about a month earlier than a lot of other people were.

ETG: COVID-19  causes blood clots in your respiratory system and a lot of other things. How did you feel about that, personally?

JS: I think like everybody else, nervous. It’s scary. I’m a first responder, too, so my first impulse was to want to get out on the front lines and help. It was really hard to not be in a position to help in the way that I wanted to help. For me, deciding to pour my heart and soul and science into these mask efforts was my way of helping because I couldn’t physically be on the front line. So I wanted to do what I could for my friends who were: the first responders, EMTs, firefighters, the people who show up on the scene and weren’t being prioritized in the triage of who needs PPE. So as a former EMT, as a first responder, I want a mask that’s going to provide me as much of a barrier to bodily fluids as I can get.

WC: Through all the interviews and things that we’ve been doing, I think the main thing I’ve found is that the people who have been getting involved with the effort of mask making, it’s become a way of coping with everything going on with the pandemic.

JS: Yeah, it’s a way to channel the energy into something positive.

WC: I had so much anxiety about everything going on. Just cutting fabric – even though it was mindless labor almost – was so calming in a way because I felt that I was helping and I was taking control.

Making Masks is Trail Magic

JS: Finding the things that you can do. As the pandemic initially was spreading, and it felt like something we couldn’t do anything about, I think for me at a secondary level – the first level was I have all this information and all this stuff about masks and my family, and all the backpacking I’ve done walking across the country three times for the Appalachian Trail, Pacific Crest Trail and Continental Divide Trail, I have pockets of family that are scattered up and down the country all over the place in rural America. They’re people who have opened their hearts and their homes and invited me in and have made me part of their family that were complete strangers. We call that trail magic.

WC: I believe it. I’m from Appalachia.

JS: So I feel like all the people who are coming together to make masks are providing a version of that trail magic on a much bigger scale. We have these resources and supplies and skills that we can put out there to try to make things just a little better even if we’re one person or one day; it’s something we can do. That part is really what renews your faith in humanity when a lot of other things in the world may not.

ETG: That’s part of why we’re doing the Summit to bring everybody together, have these conversations, but also record and celebrate. As part of it, we’re doing a giveaway: If people sign up, they get entered into a giveaway that all these companies have donated as a thank-you to the sewists who have been working so hard.

JS: A lot of people are in positions already where the need for masks isn’t as great, but that isn’t everywhere. The stuff I see on the news makes it seem like everyone that needs masks has masks, and that does not match the reality that I’m living in. The shortages are expected to continue. That gets into some of the more complicated issues of whose voices are heard and which stories are being told.

ETG: The story of the masks is really multifaceted, and I think it brings up social inequities, economic inequities, and now we’ve got politics injected into it in a really stupid way, and then all of the supply chain; so there’s just a lot to all of it.

JS: One of the questions I was not expecting was: What do you do when you get tear gas or pepper spray in your mask?

That is a really legitimate question and concern right now.

ETG: So now you need at least two masks when you go out because you’ve got to have a backup. But what do you say to that?

JS: What I say to that is there’s a lot we don’t know. I haven’t seen any studies with pepper spray and masks. But what it really means is that you should change the mask as soon as possible, especially because if you have absorbent materials, it’s going to be the gift that keeps on giving.

ETG: Polypropylene might help because it will act as a barrier more than cotton would.

JS: If it’s in a water-based or droplet-based form, it may help. Once again, this gets back into the privilege of how many masks you have. And if you don’t have a sewing machine and you haven’t been sewing your own, you may not have a dozen masks even though that’s a target that everybody should be working towards because as soon as it gets wet or dirty, you should change it.

ETG: The concern that I have is that we’re looking at these commercial masks and they’re just all over the place. A lot of them are super cheaply made and you don’t know what they made them out of. They seem kind of dangerous to me on some level. You just don’t know. There’s no rating system; there’s no requirements; there’s no standardization.

JS: All you have to do is have a label. If it doesn’t have a label telling you what the materials are and how to wash it, it is not okay. You have to be able to know what’s in it and know how to wash or disinfect it.

ETG: We’ve ordered some commercial masks, so they should be showing up at some point. We haven’t talking about shields. Tell me what your thoughts are about mask+shield. Do you think that’s a good thing?

JS: Yes. Face shields are just another piece of the puzzle. I think face shields are a good thing. The data out there says they’re not the same as masks, so a face shield and a mask is good. I am not a face shield specialist. There are other people who have done all the research and analysis there. Certainly, if you can do a mask and a face shield – eye protection is good.

ETG: Are glasses enough or do you want goggles? I’m going to be so suited up when I finally leave my house!

JS: And it’s going to be 95 degrees.

ETG: And I’m going to fall over.

JS: Here we go into another topic about heat stroke and heat exhaustion and making sure that you are hydrating appropriately. If you’re wearing a mask and/or you’re out for a long period of time, you need to drink. How do you drink without touching your mask?

ETG: We’ve seen joke ones with the straws. It’s not good. That must make you completely insane.

JS: If we’re talking about things that make me cringe, we can talk about the masks with the exhalation valves because they’re blowing all of your respiration all over everybody. We talked before about if you have just a single layer it might act as a diffuser and spread everything out, but a ventilation valve might act as a focuser.

We were talking about the straws. Anything that goes in and out through that control area of the mouth is bad.

ETG: And you know they’re going to be popular in New Orleans.

JS: Like all these things, there are better ways to do it and worse ways. How do you get the straw in without holding the bottom of the mask? Now you’re touching the mask in two places. At least minimize the points of contact. I do have some with straws.

ETG: They’re going to be on Bourbon Street, and they’re wearing a mask with a straw hole. Maybe that’s better. I don’t know.

JS: That’s that thing with why is it people are saying maybe we shouldn’t open bars. Alcohol does inhibit boundaries. People aren’t as good at paying attention, not as good at motor control. Wearing your mask while drunk.

WC: During the beginning of things really exploding, I knew people who were going to the bars, and I was like: Are you crazy? And they were like: The alcohol will kill the virus if it’s in my mouth. I’m like: Okay. That’s a strange and very risky line of thinking.

JS: It’s a common one. I shouldn’t legitimize any of it, but the proof you need your alcohol to be at for it to act as any kind of disinfectant is 160 proof.

ETG: That’s just a challenge to some.

JS: If the alcohol you’re drinking is 160 proof, then you have a lot of issues ahead of you. The chances that the behavior being engaged in while drinking alcohol of that proof is risky is high. That is true with or without COVID as an additional risk factor.

So, we’ll just say no on the alcohol acting as a disinfectant. We can dive into the data of how risk is likely to be amplified in those circumstances, but certainly it is in a lot of different ways.

So drink responsibly; wear your mask responsibly; do all the things as responsibly as you can, realizing that nothing is perfect but you’ve got to try. If we all do a little bit better as we move forward, that’s going to amplify and hopefully we get better and better and better until we get nearly there.

I’m hoping that as we go through the summer and the pace is maybe not quite as frenetic as it was at the beginning, it gives us a little bit more time to think about the whys behind the things we’re doing instead of just doing it in panic mode so that we can move forward more responsibly.

ETG: I think that’s very true. It takes time to do the science, so it’s interesting to watch what’s happening with that. To watch science work its thing, that doesn’t happen very often. My kid’s best friend’s mom asked me if I saw the ACS study on masks. This is regular conversation now, which is so fascinating and awesome in some way, right?

JS: Right. And there’s this new study that the WHO references that hasn’t made it quite into the full cycles yet.

ETG: I can’t wait to see it.

JS: The link is on that MakerMask webpage.

ETG: Well, you’re amazing, and you’ve given us so much time. We kind of super geeked out on you, and I know everybody is going to be so excited to listen to this.

JS: This is a dialog that we’re all going to keep participating in. That’s the important bit.

The post Homemade Mask Summit: Masks Unmasked appeared first on MakerMask.

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Mask-Making and Culture: The Social Context of What We Make https://makermask.org/mask-making-and-culture/?utm_source=rss&utm_medium=rss&utm_campaign=mask-making-and-culture Tue, 30 Jun 2020 01:33:05 +0000 https://makermask.org/?p=1130 In this post, we hear from Rachel Sadd (aka Crafty), who shares with us some of her experiences and observations about the social context of making masks. This is part of a series of guest blog posts where we get a chance to hear voices and perspectives about making masks more accessible.

The post Mask-Making and Culture: The Social Context of What We Make appeared first on MakerMask.

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In this post, we hear from Rachel McCrafty (aka Crafty), who shares with us some of her experiences and observations about the social context of making masks including: perception of sewists, diversity in mask making, and inequities in mask access. This is part of a series of guest blog posts where we get a chance to hear voices and perspectives about making masks more accessible.

Wow! Millions of Masks Made

As of the week of June 15th, mask-makers in the U.S. had produced 860K* cloth masks. Think about that. That number is huge even in the face of the overwhelming need. Consider all the organizing, materials, cutting, and thread snipping involved in that.

Infographic from OSMS: Worldwide Cloth Mask Production for COVID-19, March 28-June 15, 2020. (right, bottom: data table) Cloth Masks Made by Country: United States made 861K, India made 363K, Spain made 15K, Canada made 10k. (top right: bar graph) Total Personal Protective Equipment (PPE) Production Per Week, quantity in millions on the y-axis, week on the x-axis, type of PPE produced color coded in stacked bars. Majority of PPE produced according to graph is face shields, followed by cloth masks. Note, number of cloth masks made likely underreported. (bottom, left) Bar of cloth masks produced by country, contains image from chart, and small slices of data from other countries. (right) Heat maps of the US and the Globe showing areas where mask making was reported, showing data from 21 countries, with 825 separate submissions, and over 1.3 million masks made.
*Source: https://opensourcemedicalsupplies.org/impact/

Present Tense Tension

Most folks who sew know that getting the tension right is key to things going well. And navigating the context of mask making is no different.

Infographic: Present Tense Tension. (top, 3 red boxes) Validation for sewists, Diverse types of mask makers, The moment for mindful helping. (bottom, gray box) A Global Pandemic + Rapid Social Change
Factors at play

The pandemic is a tragic shared experience that has highlighted social inequity, supply chain issues, public health shortfalls, and so many other challenges in our country and around the world. The action taken to address civil rights has been profound, as has government response.  All this is happening on a scale that has never been seen before. When thinking about the social context of mask-making, I am exploring three aspects that have proved significant: perception of sewists, diversity in mask making, and inequities in mask access.

Validation for sewists

Bubbles with text: Crafty perceived as scientifically valid, Sewing as an actual skill, Sewing, including mask-making seen as more than "woman thing" by the general public, ability to effect real positive change
New spheres of influence

In the US today, handmade items often have a perception of either being low-value crafts or super high-end hipster goods. The pandemic and the rapid social change we are all experiencing has changed not only how the world sees sewists and quilters, which are predominantly women, but also how we see ourselves and each other.

One trend I observed in the maker-sphere was a realization of the level of skill that sewing takes. Inexperienced folks with skills in other areas thought mask-making was all about machine access and quickly discovered that this was not the case.

For many, this is the first time that such “traditional” or “feminine” skills have been in such dire need. Agency and action of the part of sewists showed a marked ability to help and effect change. We came through when it counted.

Diverse Types of Mask-Makers

From non-profits to church groups, and local clubs to social activists, mask makers have more than proven their commitment to harm-reduction in our communities.

What mask-makers have in common

  • Desire to help
  • Skills and time spent on sewing machines
  • Action-oriented in the face of catastrophe
  • Burn out…

What are our differences are

  • Access to resources
  • Culture of origin — many immigrants come from cultures that have strong sewing traditions
  • Religious practice or lack thereof
  • Politics
  • Working styles and language
circle graphic with text = Hobby Groups, Social Good activists, Independant home sewers, Makerspaces, Church Groups
Just a few different types of mask making groups

In the past, these differences between communities have often created silos and cliques — social divides that are being put to the test. Helping on the scale we are with supply chain gaps and grassroots efforts has different groups working in greater proximity than ever before, oftentimes trying to work with each other for the first time.

By remembering we are having different experiences, we can better appreciate each other and work together to respond to the crisis. There are many right ways to help.

Do the best you can until you know better. When you know better, do better. – Maya Angelou

We also now have an opportunity to explore thoughtfully how we are building our own mask-making communities as well as how we can be mindful about the communities we choose to serve. And make no mistake, each mask-maker is choosing what project they participate in and to whom they give their masks.

The moment for mindful helping is now

Who are your masks for?  As a significant new supplier of vital protective equipment, what are our responsibilities? What are the opportunities?

In the map below showing COVID-19 rates by Zip Code in Alameda County (CA), which areas do you think are black neighborhoods? Poor immigrant neighborhoods? Affluent white neighborhoods?

It breaks down pretty much as you might think. When I look at this map, I notice some of the highest case rates of COVID-19 in East Oakland – predominantly Black and Latinx neighborhoods, not a quarter-mile away from Alameda Island with a large population but some of the lowest rates – predominantly white, I am struck by the social and economic inequity between them.

Map of COVID-19 rates by zipcode in Alameda County, CA
Source: Alameda County Public Health Department, California. http://www.acphd.org/2019-ncov.aspx
(photo) A black 'Distill My Heart' mask made from donated spunbond nonwoven polypropylene bags, two care and use labels for masks, one in English 'Washable Mask' and one in Spanish "Mascarilla Labable", and one individually packaged 'Distill My Heart' masks (blue) with label in a ziplock bag that is ready for distribution
Distill My Heart Mask – NWPP Mask with English and Spanish Packaging Labels

When designing the Distill My Heart Mask project I and my partners at Circuit Launch had this inequity in mind. We spoke with local healthcare workers and social good organizations. We actively chose to prioritize the least resourced populations in Oakland and the East Bay.

Once we chose who we were serving, we needed to find out the best way to do it. That drove our material choices, our pattern choices, and how we packaged our masks.

We asked ourselves:

  • Who the user was and what resources did they have for cleaning and reuse?
  • What did distribution look like and were the contamination risks?
  • Who was already doing distribution of aid?
  • What was the best balance between material, fit, and production?
  • What support did sewists need? Could we recruit sewists from an already overtaxed volunteer base? What did contracting look like?

This was the result:

  • Material: NWPP supplied by American Distilling Institute conference bags organized by MakerMask.org. This provided masks with good droplet barriers that could be easily disinfected in a pot of boiling water, and rapidly dried without a dryer.
  • Open Source pattern from Common Sewing. This pattern had a range of fit, a filter pocket, and was production-proven by the Orlando Facemask Strong project.
  • Packaging and Labeling. We individually wrapped the masks for safety in distribution. The packaging is in English and Spanish. This made for safe distribution to un-housed folks and through agencies where access to laundry facilities are not likely to be available. This also made it an ideal mask during protests and was distributed to street medics.
  • Producing quality mask kits for sewists with laser cut pattern pieces, threading tools, and most importantly, a sample of a finished mask. This reduced the barrier to entry for a wide range of volunteers. Offering a piece-rate where applicable for sewing.
  • Distribution to at-risk communities through established social good organizations. This required establishing new relationships and cultivating new volunteer resources.
  • Progress to date. The Distill My Heart Project has provided over 1900 masks to under-resourced Oakland communities to date and will provide over 3400 before the project transitions to a more evergreen project run by Ace Makerspace in North Oakland.

 

Moving forward with intention

The Distill My Heart Mask project is just one case study. We (all mask-makers) now have an opportunity to explore thoughtfully how we are building our own mask-making communities, as well as how we choose what communities we serve and how. This may take investigation on your part, careful listening with a humble ear to what our neighbors need and have to offer.

And it isn’t all about equity and altruism. Under-resourced populations are more likely to have to continue working, have fewer options for social distancing, and are more likely to overwhelm inadequate healthcare systems.

We don’t have to be perfect right out the gate, but as thinking, caring people, we have a great opportunity to put our time and energies to good use in ways that build stronger communities.

Photo of Rachel Sadd, sitting at a table and smiling, with "Be Nice or Leave" in large pink letters highlighted as a banner in front of her. The color of the text matches the vibrant color of the pink streak in her hairAbout the author

Rachel Sadd, aka Crafty, is a Bay Area based artist, designer, and maker. A long-time builder of art and community, Rachel prioritizes the connection that comes from building and designing together. Her unique energy and willingness to try things inspire those around her to engage their creativity and stretch their skillsets. Equally engaged by beauty and utility, she creates projects which span genres and challenge ideas about art, craft, and culture. When she isn’t creating she brings these same values to leadership at Ace Makerspace in Oakland, CA as the Executive Director.

Links

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3 Easy DIY Mask Tests https://makermask.org/diy-mask-tests/?utm_source=rss&utm_medium=rss&utm_campaign=diy-mask-tests https://makermask.org/diy-mask-tests/#comments Thu, 25 Jun 2020 01:15:09 +0000 https://makermask.org/?p=702 In an ideal world, the safety and efficacy of all of the fabrics and materials used in handmade masks for COVID-19 would be tested using the same standards and facilities used by researchers and large manufacturers. Unfortunately, very few people have access to these resources. In this post we provide instructions for three easy DIY […]

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In an ideal world, the safety and efficacy of all of the fabrics and materials used in handmade masks for COVID-19 would be tested using the same standards and facilities used by researchers and large manufacturers. Unfortunately, very few people have access to these resources. In this post we provide instructions for three easy DIY mask tests to evaluate key features of masks materials and fabrics that can be done at home.

Illustration of supplies used in DIY mask test for droplet resistance. Stopwatch, teaspoon, cough syrup cup, and cough medicine syringe Illustration of supplies needed for DIY mask tests of breathability and filtration including: yard stick, tape, elastic band, and cardboard tube

 

Note: Boxes with additional content, tests, and information are located throughout this document. click on the “+” to expand the box for the bonus materials. Once expanded the content can be contracted by clicking on the “-“. 

The Science Behind the Tests

COVID-19 is primarily transmitted via respiratory droplets. Face masks for COVID -19 are designed to cover the mouth and the nose and act as a barriers to droplets to help reduce the spread of COVID-19. Although these fabric masks are intended for use as source control to contain users droplets (i.e. egress of droplets) some designs, such as those with water-resistant outermost layers, may help keep droplets from the outside world to the users mouth and nose (i.e. ingress of droplets). The three key requirements for Masks for COVID-19 are: water resistance, breathabilty, and filtration.

Water Resistance: Materials can be characterized by whether they repel water (hydrophobic) or attract water (hydrophilic). Hydrophobic materials can be used to help act as barriers to liquids like droplets. Hydrophilic materials that absorb liquids can help contain your own droplets for source control.

  • Hydrophobic Materials: Water beads up on the surface of hydrophobic materials and they are generally considered water-resistant. An example of a hydrophobic material used in masks is spunbond nonwoven polypropylene (NWPP).
  • Hydrophilic Materials: Water spreads out on the surface of hydrophilic materials and they are generally considered absorbent. An example of a hydrophilic material used in masks is cotton.

Breathability: Breathability tests assess the breathing resistance of a material. In other words, they measure how difficult it is to breathe through a material. Breathability is critical for materials (and combinations of materials) used in masks. Masks that are more breathable are more comfortable to wear, especially for extended periods of time. Masks that are not breathable should not be used! .

Filtration: Materials with a high capacity for particle filtration are those that prevent, or significantly reduce, particles from passing through the material. These materials are ideal for use as barriers to dusts, powders, and other minute solids that could cause or exacerbate breathing difficulty.

It is important to consider the performance of masks and materials in all three of these areas. Evaluation of any one test alone is insufficient. Quick qualitative checks may help eliminate the worst mask materials, but are challenging to quantify. In this blog post, we provide details for conducting 3 DIY mask tests that are more quantitative to guide users as they evaluate mask fabrics, materials, and layering options.

These DIY tests are not intended to replace regulatory testing and do not guarantee the safety or effectiveness of masks or mask materials. However, they may aid mask makers in making decisions about which fabrics and materials to use in their masks. The results from all three tests should be considered when selecting materials. In addition, consider the durability of the mask materials, and their suitability for re-use (e.g., cleaning and disinfection; see bottom of page). Masks that are not breathable should NOT be used!

Quick Pass/Fail Material Quality Checks

Quick qualitative checks may help get a general sense of the properties of masks and mask materials, and help to rule out materials that are likely to perform poorly. As with other tests of masks and materials, consider the results from all three checks when deciding which materials warrant further investigation.

  1. Water Resistance Check: Flick water at the mask materials, if the water beads up on the surface, the material is water-resistant. If the water quickly spreads out across the material creating a wet spot, it is hydrophilic or absorbent.
  2. Breathability Check: The WHO suggests that you can hold the material/mask up to your mouth and try breathing through it to test breathability. Caution: don’t inhale air through fabrics until and unless you have first cleaned it AND made sure there are no potential inhalation hazards.
  3. “I See The Light” Filtration Check: Hold the material up to the light, if you can clearly see the shape of the light through it, it is not likely to be a great filter material. The more light that is blocked by the material, the better filtration it is likely to provide. Don’t forget, always check breathability before using any material in masks!
DIY Calculation of Fabric Weights (gsm)

Fabrics may be characterized using a standard measurement for fabric weight, grams per square meter (gsm). If the gsm of a given fabric is not provided by the manufacturer, it can be calculated at home using a digital kitchen scale and a ruler.

Procedure

  1. Select a rectangular sample of fabric that weighs at least 5 grams.
  2. Measure the length and width of the materials in meters (or convert to meters from cm or inches)
  3. Calculate the area of the material (in square meters) by multiplying the two lengths together.
  4. Then weigh the material on the kitchen scale in grams (or convert ounces to grams).
  5. Finally, divide the weight in grams by the area in square meters to get the ‘weight’ of the material in gsm!

Materials and Supplies for DIY Mask Tests

The items listed below will be needed for each of the DIY mask tests. Additional items required for a specific test will be included in each test section.  You may reuse the same supplies to conduct all of your tests, or use a fresh set for each test.

For a deeper dive into the science behind mask materials and the importance of each test, read more at: The Big 4: Criteria For Community Mask Materials.

Materials/Fabrics to Test:

  • Cut a 4” (10 cm) square of each material/fabric for testing.
    • Paper towel
    • Woven cotton fabric
    • Spunbond nonwoven polypropylene (NWPP) fabric
    • Plastic wrap

Other Supplies:

  • Scissors
  • A kitchen scale (measures grams)
  • A glass or jar
  • Clock, timer, or stopwatch
  • Elastic or rubber bands
  • 4 – Cardboard tubes (e.g. from toilet paper rolls)
  • Yard stick or tape measure
  • Pea-sized lint ball or cotton ball
  • A notepad or table to record your results

1. DIY Mask Tests: Water Resistance

Infographic with two panels: "Benefits of Water-Resistant Materials in Mask Production." Top panel: (left) person spraying droplets from their mouth, (right) zoom in of droplet showing a virus particle in the droplet. Bottom panel: (title) Nonwoven polypropylene, (left) person wearing a MakerMask: Surge pleated mask, (right) water droplets rolling off of the water-resistant nonwoven polypropylene materials used in MakerMask designs

Objective

Use this test to determine how well a material can keep water from crossing from one side of the mask/material to the other.

Materials and Supplies:

  • Materials/fabrics for testing
  • Glass or jar
  • Elastic bands
  • A coin (e.g., a quarter)
  • Measuring cup and cold water
  • Timer
  • Graduated medicine cup
    • alternatives: syringe, pipette, or teaspoon

Procedure:

  1. Set out the four materials for testing, the elastic bands, and an empty glass.
  2. Fill a measuring cup with cold temperature water and bring it back to your workspace.
  3. Take one of the squares of material, place it over the mouth of the empty glass, and then place the elastic band around the rim of the glass to hold the material in place. (Note: a coin, e.g., a quarter, can be used to create a small dimple in the center of the mask material)
  4. Measure 10 ml or 2 (US) teaspoons of water, and pour it onto the material covering the glass.
  5. Set a timer for 60 seconds after pouring the water on top of the material.
  6. Wait for 60 seconds to elapse then, if there is any water on top of the material (i.e. outside the cup) pour it into the graduated medicine cup and record the measurement in your results table (“Repelled Amount”).
  7. Carefully remove the material from the mouth of the glass and set to one side.
  8. Pour any water inside the glass into an empty graduated medicine cup and record the measurement in your results table (“Collected Amount”).
  9. Calculate the amount of water absorbed by the material and enter the value into your results table (“Absorbed Amount”):
    • “Absorbed Amount” = “Starting Amount” – “Repelled Amount” – “Collected Amount”
  10. Dry off the inside of the glass and the medicine cup, and repeat the process for each material you want to test.
Photo of supplies used in the DIY mask test of water resistance including elastics, fabrics, and glass jars photo showing paper towel across the top of a jar, held there with an elastic band Photo of a mason jar covered with a piece of cotton for the DIY mask test of water resistance illustration of measuring tools used in DIY mask test Photo showing Hydrophilic Cotton Material with water absorbed into it Photo of Hydrophobic spunbond nonwoven polypropylene material

 

Results & Discussion

Results

Here is an example of test results for the materials listed. How do your results compare to ours?

Material

Water Measurements & Calculations

Material Classification

Starting Amount (ml) Repelled Amount (ml) Collected Amount (ml) Absorbed Amount (ml)
Paper Towel 10 0 1 9 Absorbent
Cotton Cloth 10 0 4 6 Absorbent
Spunbond NWPP 10 10 0 0 Water-resistant
Plastic Wrap 10 10 0 0 Water-resistant
Are your results repeatable and reproducible? One test is never enough. Repeat the test multiple times and take the average of the amounts (standard deviations are good too!) for each material to see if you can determine if your first results are consistent.

Discussion

Which materials had the most water in the glass at the end? These materials didn’t block water from crossing from one side of the mask to the other, and are poor barriers for water-based droplets.

  • Water-Resistant Materials: Of the four materials you tested, which ones had the most water on top of the fabric at the end? The most water resistant materials will have the most water on top of the glass at the end, and the least amount of water inside the glass at the end. These materials are the most hydrophobic, and act as a  barrier to water droplets, preventing them from passing from one side of the mask material to the other. According to the WHO guidance, hydrophobic materials can be used for the outermost mask layers, but they must be breathable. Would all of the hydrophobic materials make good mask layers? Why or Why not.
  • Absorbent Materials: Which materials absorbed the most water? These materials are the most hydrophilic and will be the best at absorbing and containing droplets. According to the WHO guidance, hydrophilic materials can be used for the innermost mask layers. In addition to being hydrophilic, materials used in reusable masks must be washable. Are all of the hydrophobic materials washable? How would you test that?

Additional Questions and Considerations

  • Curious to know how other materials may perform? Try some!
  • Do you get the same results if you use multiple layers of the same material? Try it and find out.
  • What about different combinations of mask materials and layers? Try it and find out.

A material MUST be breathable to be a good mask material. Which of these materials do you think will be breathable? Continue to test number 2 to find out!


2. DIY Mask Tests: Breathability

Illustration showing the breathability of a mask materials for fabric masks, showing air flowing through it

Objective

Use this test to determine which material has the breathability of mask materials by measuring how far you can blow a small object (high breathability = longest distances).

Materials and Supplies:

  • Masking tape
  • Test Materials
  • Elastic or rubber bands
  • 4 – Cardboard tubes (e.g. from toilet paper rolls)
  • Yard stick, ruler or tape measure
  • Pea-sized lint ball or cotton ball

Procedure:

  1. Clear a space on a large flat surface, place a strip of masking or painter’s tape on the surface (at least 1” or 2.5 cm from an edge) and then set your yardstick (or other measuring device) next to it so that the zero-marker is aligned with the far edge of the tape.
  2. Wrap each square of material over one end of a cardboard tube (four tubes in total), and secure it with an elastic band.
  3. Find a ball of lint, or cotton ball and roll a piece of it into a ball that is about the size of a pea.
  4. Place the cotton or lint ball on the far edge of the tape. This position is the ‘zero-marker’ and should correspond to zero on your measurement device (see illustrations below).
  5. Place the end of the cardboard tube wrapped with your material at the other edge of the tape (the near side of the tape).
  6. Blow through the tube using one normal breath. When finished,
  7. Measure the distance the ball rolled.
  8. Record this distance in your results table.
  9. Replace the ball at the zero-marker and repeat for each material until all materials have been tested.
illustration: supplies used for DIY testing illustration: setup for the DIY Mask Test for breathability. Includes cardboard tube with material mounted over the end, elastic band, tape, and direction of air being blown into the tube
Results & Discussion

Results

Here is an example of test results for the materials listed. How do your results compare to ours?

Material

Breathability

Distance Rank
Paper Towel 53 cm Ok
Cotton Cloth 43 cm Ok
Spunbond NWPP 76 cm Best
Plastic Wrap 0 cm Worst

Are your results repeatable and reproducible? One test is never enough. Repeat the test multiple times and take the average of the distances for each material to see if you can determine if your first results are consistent.

Discussion

Which materials were you able to blow the ball the furthest with? These materials have the lowest breathing resistance and are the most breathable (GREEN = good).
Zero inches is a FAILING score. If you are not able to breathe through the material it should not be used for face masks. For example, plastic wrap should not be used in face masks no matter how good it is at blocking water or particles because it is not breathable.

Additional Questions and Considerations

  • Is this test qualitative or quantitative? Is it repeatable?
  • How large of a breath did you use? One breath isn’t a standardized measurement since your breath and my breath are probably not the same. Is it more repeatable is you use the largest breath you can? Does it work if you use a turkey baster instead of a breath? What improvements can you think of to make this test more repeatable?
  • Would measurements of the cotton or lint ball help make experiments more repeatable across households? Which measurements would you use?

 


3. DIY Mask Test: Filtration

illustration showing red particles being partially filter by a piece of fabric for the DIY Mask test of filtration

Objective

Use this test to determine how well a material can keep particles (< 50 μm) from crossing from one side of the mask/material to the other.

Materials and Supplies:

  • Choose a powder with small particle size (e.g., baking powder)
  • A magnifying glass (optional)
  • A measuring teaspoon
  • A bowl or pan or a couple pieces of dark-colored paper
Deeper Dive: Selection of Particles for DIY Test

Although it is challenging to test materials against the small particles (<3μm) used in formal mask tests, many of the dry ingredients used for cooking have individual particle sizes that are on the order of microns. For testing masks, consider using the powders with the smallest particle sizes you have access to. The finest powders we had access to were baking powder and confectionery sugar (baking powder worked better because it clumped less).

Particle Source

Typical Particle Sizes (μm)

Corn Starch 0.5 – 10
Baking Powder 5 – 50
Powdered (Confectionery) Sugar 3 – 50
Baking Soda (grade 1) 44 – 70
Wheat Flour 200 – 300
Crystallized (white) sugar 400

Note: Particle sizes for a given ingredient may vary, however, many baking particles are passed through sceens/meshes that limit the particle size distributions according to ASTM standards (A deeper dive with more information is available in the references at the end).

Procedure:

  1. Reuse the same cardboard tubes wrapped in material from the “Breathability Test”
  2. Setup your test area with a bowl to contain any potential mess, a measuring teaspoon, and some of your powder.
  3. Hold the first cardboard tube covered with material over the top of the bowl, so that the end with the material is facing downwards.
  4. Scoop one teaspoon of powder into the open end of the cardboard tube.
  5. Using a timer, shake the tube of powder for 30 seconds above the bowl.
  6. Make note of whether you observed any powder accumulating in the bowl.
    • If powder is obviously cascading through the material, the material has poor filtration characteristics.
    • If a measurable amount of powder accumulates, measure it.
  7. Dump the powder remaining in your tube into an empty bowl. Then place the cardboard tube with the material facing upwards on a flat surface. Observe whether or not particles of the powder passed from the inside of the tube to the outside surface of the material. Write down your observations. (A magnifying glass may be used to aid observations if needed).
  8. Repeat for each material.
  9. Once you have completed the test with each tube and material, observe how much powder has passed through each material and record a rank for each material in your results table.

 

 

Illustraion: DIY Mask Test for Filtration Set Up with cardboard tube, mask material, teaspoon full of powder and a bowl down below

Photo: DIY Particle Filtration Test: 100 gsm spunbond NWPP didn't allow any particles to pass through Photo: DIY Particle Filtration Test: Woven Cotton showing lots of confectionary sugar passing through

In the video below, you will see that the setup on the left (spunbond NWPP) has high particle filtration. The powder remains in the tube and the glass below remains clear and clean.  In contrast, the setup on the right, with low particle filtration, passes a large quantity of powder through the material (cotton) into the glass below, and the material itself is covered in powder during and after the test. 

 

Results and Discussion

Results

Here is an example of test results for the materials listed. How do your results compare to ours?

Material

Particle Filtration

Rank
Paper Towel Good
Cotton Cloth Worst
Spunbond NWPP Good
Plastic Wrap Best

Discussion

Did you see a difference between the materials you tested? Ideally, we would be able to measure (quantify) the difference between the amount of powdered filtered by the different materials. However, depending on the materials tested the amount of powder in the bowl may not be measurable. In this case, observations are recorded.

Of the breathable materials, the spunbond NWPP and the paper tower performed the best and cotton performed the worst. Both spunbond NWPP and cotton come in many different variations. Some do better, some worse. How did yours perform?

As with the water-resistance test, it is important to note that even though plastic wrap blocks particles, it should NOT be used in masks. If a material is not breathable it should not be used in masks. 

Additional Questions and Considerations:

  • Curious to know how other materials may perform? Try some!
  • Do you get the same results if you use multiple layers of the same material? Combinations of mask materials and layers? Try it and find out.
  • Can you think of other ways to more quantitatively and consistently measure particle filtration with things commonly available at home?

 


Conclusion

The DIY tests outlined here demonstrate some of the core principles behind mask science.  Of course, these tests are not designed as replacements for standard laboratory testing, but we hope they can aid in your selection of mask materials, or at least give you more insights to the “why” behind the recommendations you are hearing in the news.
  1. Water-Resistance: According to the WHO, water-resistant (hydrophobic) materials should be used for the outermost layers of the mask, hydrophilic layers should be used for the innermost layer.
  2. Breathability: If a mask is not breathable, it should NEVER be used. Although breathability of each individual material is important, it is also important to verify that the combination of desired materials is breathable as well.
  3. Filtration: Particle filtration is what helps block droplets and particles from traveling through your mask. In addition to evaluating individual layer performance, be sure to evaluate the performance of your multi-layered designs.
Have you found other helpful DIY home tests for evaluating the function of masks and mask materials? Share your favorites in the comments or email them to us. The more quantitative and repeatable the better!

Illustration: Person wearing mask with clip art of additional information

Additional DIY Mask Tests Under Consideration

DIY Material Shrink Test (Washing/Disinfection, Quantitative)

Mask materials/fabrics should be cleaned according to manufacturer’s guidelines. If manufacturer’s guidelines are not available test a set of samples of mask materials/fabrics using the methods proposed for cleaning/disinfecting the mask. All mask materials should be able to withstand high temperature > 60°C washing through multiple cycles according to the WHO guidance. For MakerMask designs, disinfection by boiling or steaming is recommended (For more information about cleaning and disinfection see: Fabric Face Masks: Cleaning and Disinfection.)

Method: As a simple test of mask material suitability for boiling/disinfection:

  1. Cut out five or ten squares (5 cm x 5 cm) of each material to be tested.
  2. Then either boil (submerge in boiling water for 10 minutes) or steam (at 15 psi, 121°C for 15 minutes) the material. For more information on these disinfection procedures and a deeper dive into the science behind them check out: The Deeper Dive on Fabric Mask Cleaning and Disinfection
  3. After treating, measure the dimensions of each square and note any obvious changes in material properties.
  4. (Ideal) Repeat the 3 DIY tests of the materials before and after cleaning/disinfection.

Infographic: MakerMask Recommended Mask Disinfection Methods. Boil: submerge in boiling water for 10 minutes. Autoclave: follow facility infection control policies and autoclave (steam) at 15 psi, 121C for 15 minutes.

Results: We evaluated 4 material types, three 40 gsm bandage materials donated from Hollister (a,b,c), and one 90 gsm material sourced from a reusable conference bag (d).

  • a) 40 gsm translucent white spunbond NWPP
  • b) 40 gsm tan spunbond NWPP
  • c) 40 gsm beige spunbond polyethylene
  • d) 90 gsm navy blue spunbond NWPP from reusable bag.

After one 15-minute steam disinfection cycle (e.g., Instapot), all ten samples of polyethylene (c) decreased in size from 5 x 5 cm to 3.5 x 3.5 cm. However all 40 samples of spunbond polypropylene remained the same size over the course of five disinfection cycles. Caution: Significant off-gassing/odor resulted from steaming the polyethylene. Do not steam polyethylene. In general, if off-gassing is a concern, use the lowest effective temperature disinfection/sterilization methods. Recall, longer durations of heat exposure are required at lower temperatures. 

Photo: Squares of PP in the center stack shrunk when washed at sterilization temperatures.

DIY Durability Quick Test (Washing/Disinfection, Qualitative)
  1. A quick qualitative test of the durability of a materials/fabrics for mask use is to check to see how easily the material tears. If it tears easily, it isn’t likely to stand up to very many uses/cleaning/disinfection cycles.
  2. Another way to look at durability, is using a fingernail to scratch along the surface of the material, if a lot of fibers are easily dislodged, it is unlikely to hold up to the wear and tear of reuse. If small fibers are released and become airborne, it may pose an inhalation use to mask makers and mask users.
  3. Finally, using the same set-up used for the DIY mask tests for water resistance, coins of known weights can be added on top of wet materials, and the weight at which the coins rupture the wet material and fall into the jar below, or the weight at which the elastics can no longer hold the material across the jar can be calculated. If the coins successfully perforate the wet material, the material is not suitable for use in reusable masks.
DIY Hydrostatic Head Test (Water-Resistance, Quantitative)

Recommended as a pre-test for fluid resistance (ASTM F1862) for proposed surgical masks. This is a home DIY version of one of the water resistance test used to assess the water penetration resistance of surgical drapes and gowns.

Materials: clear rigid tube (or other clear vessel with open top and bottom), sharpie, ruler, razor blade, elastic bands, mask materials, funnel, cold water, glue gun (optional). The clear tube should be at least 20 cm tall. For the DIY test, the open-ended tube was crated by using a razor blade to cut off the bottom of a ‘bubble stick’ tube. A glue gun was used to coat the bottom of the tube to close gaps and create a smooth mounting surface for mask materials at the bottom of the tube. Then, the ruler was used to measure 10 cm and 20 cm up the tube.

Procedure: Materials were affixed to the bottom and water was poured through the funnel into the tube up until the point that water began dripping through the material at the bottom. The height of the water column was then recorded in cm H20 to indicate the pressure at which water penetrated through the mask materials.

Example Results: Three layers of 100 gsm spunbond NWPP was able to support > 20 cm H20, whereas 3 layers of 80 gsm spunbond was able to support < 15 cm H20.

photo: DIY hydrostatic head test evaluating spunbond NWPP and a 20 cm water column

DIY Blood Gases Test (Breathability, Quantitative)

Although quantitative DIY mask tests of breathability and CO2 accumulation are challenging in home settings, a simple DIY test monitoring the functional breathability of your mask may be possible at home by monitoring blood oxygenation saturation levels (O2 sats) using a pulse oximeter. Conveniently, pulse oximeters for home use are widely available online for ($20 – $50). By monitoring your heart rate and 02 sats before, during, and after mask use of specified duration and/or activities you may be able to gain insight on the breathability of your mask. Ideally, both your heart rate and O2 sats will be the same with and without the mask during a given activity. If the mask is negatively affecting functional breathability, I would expect to see decreased O2 sats and/or elevated heart rates relative to unmasked conditions.

Note: This test is to satisfy your own curiosity and in no way is an endorsement of, or instruction for, clinical or human testing. Human testing requires special considerations of CONSENT and PRIVACY and RISK and ETHICS and cannot be recommended or endorsed by the MakerMask team. Insert ALL disclaimers here.

Photo: Example Pulse Oximeter for DIY Mask Tests of Blood Gases

DIY Vacuum Suck Test (Filtration, Semi-Quantitative)

Pour a fixed amount of powder of known particle size into a bowl. Cover the end of a vacuum with mask materials of interest. Try to suck up as much of the powdered material as possible during a fixed amount of time (e.g., 15 seconds or 30 seconds). Then, measure the amount of powder remaining after the fixed time interval. For qualitative assessment, visually inspect the inside of the face mask material for powder residue when done. Caution: Check with vacuum manufacturer for suitability for this use; materials that are not breathable may damage vacuum cleaner function.

Additional Information and References

Kitchen Particle Size Additional Information

Kitchen particles are passed through sieves (meshes) to ensure that the particles, or grains, of the dry materials all fall below specified maximum sizes. The distribution of particles sizes is typically centered well below the maximum mesh size used to filter them.

Table containing the conversations from ASTM standardized mesh sizes to microns

References:

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Masks for the Blind During the COVID-19 Pandemic https://makermask.org/underserved-communities-masks-for-the-blind/?utm_source=rss&utm_medium=rss&utm_campaign=underserved-communities-masks-for-the-blind https://makermask.org/underserved-communities-masks-for-the-blind/#comments Wed, 17 Jun 2020 22:44:31 +0000 https://makermask.org/?p=889 In this post, we hear from Matt White, who shares with use some of his experience and observations about masks for the blind. This is part of a series of guest blog posts where we get a chance to hear voices and perspectives about making masks more accessible. With government agencies around the country and […]

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In this post, we hear from Matt White, who shares with use some of his experience and observations about masks for the blind. This is part of a series of guest blog posts where we get a chance to hear voices and perspectives about making masks more accessible.

Matt White with his Seeing Eye dog Yoshi, with a full pack, backpacking on the Appalachian Trail in Pennsylvania

With government agencies around the country and around the globe adopting policies that recommend, or in some cases mandate, the use of masks by the general public to limit the spread of SARS-CoV2, it is important to consider, and address, mask accessibility issues faced by underserved communities.

Full disclosure, my name is Matt and I am blind, have been since birth. Although in many ways my experience with masks during the COVID-19 pandemic is similar to that of my sighted peers, I’ve observed some areas where accessibility could be improved, and discovered some unexpected challenges being faced by some people within the blind community.

In this post, I share some advice for mask makers based on my personal experience, and discuss the need for additional research to investigate emerging concerns about the effect of face masks on spatial awareness.

Advice for Mask Makers

My advice for the maker community is to strive to make information and designs as accessible as possible. When writing instructions, do your best to make the text stand alone, with images as supporting material, not the core of the presentation. Describe your product using phrases that make sense tactilely as well as visually.

More specifically, to improve accessibility for people with visual impairments take into consideration:

Information Access: Do words alone convey all of the important content in your social media posts? On your website? Include descriptive captions of all the images, memes, and diagrams shared. For web design, use well-captioned images, pay attention to text lay out, and use headings to make navigation more logical.

Tactile Cues: Can you put on, and take off, your mask correctly in the dark with your eyes closed? If not, consider making some changes to the mask design.  Indicate which side goes up using queues that are interpretable by blind and other tactilely oriented consumers. If there are differences between the inside and outside of the mask, those should be indicated as well. Finally, be descriptive when providing orientation directions for your product.

Masks for the Blind: The face mask on the left includes a tactile cue, a sewn on strip of bright yellow piece of fabric on the outside top of the mask... The mask on the right doesn't include extra tactile or visual orientation cues

My Experience with Masks

My specific experience has shaped my perspective on finding information about mask designs, wearing masks, and mask maintenance. When it comes to information access, finding mask designs isn’t an issue, there are tons of DIY mask designs out there. The problem is that the majority of the information about mask designs is conveyed with images, photographs, and diagrams that do not translate well into text.

Similarly, a lot of the information and instructions for wearing masks correctly (i.e. donning and doffing) is provided exclusively with visuals and embedded within infographics. Without previous mask experience, it probably would have taken me a while to sort out what I was supposed to do with the strange piece of cloth with strips hanging off the edges that people call a mask.

Luckily I had prior hands-on experience with masks so already knew how to safely put on/take off masks. As a result, when my MakerMask: Surge arrived, I pulled it out of the box and was able to identify the various components of the mask to correctly orient it: the nose bridge should be a stiffened section at the top of the mask, the pleats should be designed to fall down and away from the nose (logical since you don’t want gunk collecting in the pockets created by the pleats), and that the seams would be palpable on the inside of the mask and not the outside.

Masks for the Blind: Matt White sporting a blue nonwoven polypropylene face mask for COVID-19, a MakerMask: Surge, outside of his Washington D.C. apartment

Mask Maintenance

For mask maintenance the cleaning/disinfection is not much of a challenge; if you can boil pasta, you can disinfect your NWPP mask. Although I have to admit, I use my Instapot to disinfect my mask, which is even easier. Inspecting the mask for wear and tear is more of a challenge. Most instructions direct the user to “visually inspect the mask for wear and tear,” which doesn’t work for me. Instead, I take extra care with hand hygiene and palpate the mask, feeling for holes, areas where the material is thinning or fraying, or any other signs of changes to the texture and quality of the materials.

Miami Lighthouse for the Blind’s technology manager Jorge Hernandez walks in Miami with a long cane. COURTESY MIAMI LIGHTHOUSE FOR THE BLIND

Emerging Questions: Masks and Spatial Awareness

For most people, the sense of sight predominates their spatial awareness and the strategies they use for navigating through their daily environments. However, cues from other senses including tactile cues from touch, auditory cues from hearing, and olfactory cues from smell can all be used for spatial awareness (e.g., the perception of the relative locations of oneself and other objects in ones environment) and navigation.

Masks for the Blind: Man wearing sunglasses and face mask for COVID-19 navigating with white caneNavigating while blind relies on a few different skills, some taught, some learned. Typically, a person who has formal “mobility training” is taught to use a cane. The iconic white cane is held out in front of the blind person and is used to detect objects in the path of travel. One of the standard techniques involves keeping the cane’s tip in contact with the ground, sweeping it back and forth, with the goal of locating obstacles, drop-offs, that sort of thing. The cane tip can also be lifted slightly off the ground and tapped.

A cane is an extremely useful tool for finding obstacles, but it does not tell you much about your environment unless it actually collides with something. This is where another skill comes into play, something that I usually call “passive sonar” but that is more commonly known as echolocation.

As you are moving through your environment, sound waves are constantly moving around, emanating from their source, bouncing their way to your ears. As this article points out, “Some blind humans have developed echolocation, as a method of navigation in space.”

The way this “perception of far space” generally works is that a blind person (or a sighted person trained not to override this sense) hears the sounds as they bounce off of objects in their environment, including themselves. The brain processes these sounds, and helps construct a map of the environment, letting you know that there is, for example, an open space to your left, that a tall and narrow object is in front of you, or that there is some sort of object moving away from your right-side.

So, what does this have to do with wearing a mask? Starting in late April, I began reading accounts from blind people on social media indicating that their sound-based spatial awareness seems to be compromised when wearing a mask. Blind mask wearers report having difficulty perceiving distances to objects, leading to unfortunate head-meets-pole incidents, among other oddities.

This immediately sparked my curiosity, if for no other reason than that I, as a blind mask wearer, had never experienced any such issues. I responded to a few of the comments, asking for more information—what type of mask was it, what was it made of, how was it attached, etc.

Armed with a handful of responses, I reached out to Dr. Jocelyn Songer, founder of MakerMask.org and a long-time friend. With her background in auditory research, I thought she might have some ideas on what was causing the altered perception. One potential cause came to mind, that the cotton material of the typical homemade face mask was likely to absorb quite a bit of sound, altering the perception of sound and interfering with the blind person’s spatial awareness. She also suggested that olfactory spatial cues would be modified by the masks (you don’t smell other people, e.g. perfume and cigarettes, until they are closer to you), as would any tactile cues from the face (like the warmth of the sun, or wind, on the face).

Matt White and his Seeing Eye dog Yoshi hiking on the Appalachian Trail, at the Mason Dixon Line, with Dr. Jocelyn Songer

Since MakerMask designs rely on non-woven polypropylene (NWPP), Dr. Songer thought it might be useful to send a handful of NWPP masks out to blind people reporting these issues. The hope is to see if there will be an appreciable difference in the wearer’s spatial awareness. At this point, we are still in the information gathering phase. I am hopeful that working with the MakerMask team to investigate or identify solutions for unique challenges like this, we can address the issues facing the blind and other underserved communities.

Additional Information and Perspectives

There is very little information about the experiences of other blind people navigating during the COVID-19 pandemic. We found this one video discussing COVID-19 from the perspective of a blind woman in Hong Kong, but it wasn’t very accessible for English-speaking blind audiences (it had English subtitles, but no transcript or English audio). The link to the video, as well as the transcript (thank you Dr. Songer) are included below:

Coronavirus: Trying times for the blind and visually impaired who rely heavily on sense of touch (posted April 16, 2020) by the South China Morning Post:

“Simple coronavirus prevention tips such as: place the coloured side of your mask to the front” or “keep a safe distance from others” are impossible to follow for people who are blind or visually impaired. Individuals from Hong Kong’s blind community recently explained how their dependence on non-visual environmental cues, including sound or touch, becomes even more challenging when the world is fighting a deadly Covid-19 pandemic.”

Transcript of Video
[Lin, a blind woman in Hong Kong navigating in and around the city with a cane] “My life is heavily affected by the coronavirus pandemic. Obviously, I alawyas need to wear a mask when I go out. Before, I wouldn’t wait until my hands were foamed up with soap as I washed them. But now, I have to wash my hands all the time. And I don’t grab as many handrails on stairs and escalators. I used to hold on, but not now. I feel them with my cane, and then take a step when I feel it’s right. But sometimes I still must hold the handrail. I received a message saying that it’s safer to use my left hand to touch things and the right hand to eat but I don’t think that works. I usually need my mobile phone to tell my location, or for apps to help me read signs in front of me. I find it hard to use separate hands for touching public and personal items.”

[Shanshan Kao, the reporter ]Lin started losing her sight 20 years ago, to the genetic disorder retinitis pigmentosa. Lin says her vision now is like looking through thick, dirty glass.

[Lin ] “I can hear if a person is wearing a mask, unless the mask is too thin. Sometimes there might be a group of people standing in the middle of the road, and I want to stay at least two meters away from them, but the direction I want to go is blocked by a wall. I know where the people are when they walk, but I don’t know where to go to stay clear of them. If I take a lift (elevator) at a new place, and if the buttons are covered by a piece of plastic, I can’t feel the Braille. This should be for the ground floor.”

[Shirley Tsang, Director, Rehabilitation Services, The Hong Kong Society for the Blind.] Actually, the coronavirus affects the visually impaired just like it does everyone else. But instead of only worrying about avoiding infection, they must touch things while they are out. So that means they have a higher chance of coming in contact with microbes.

[reporter ] The Hong Kong Society for the Blind offers audio information and Braille pamphlets about Covid-19. They include tips on how the visually impaired can better protect themselves against the disease.

[Shriley] “We usually receive anti-pandemic tips online through news reports, but they are not enough for the visually impaired. They mention things like the correct way to wear a mask is with the coloured side to the front, but many blind people can’t see the color of the masks. Or how can they keep everything clean when they return home after being out using a guide dog or a white cane? General tips to fight infection don’t cover challenges like this.”

 

Link

References

  • Flanagin VL, Schörnich S, Schranner M, et al. Human Exploration of Enclosed Spaces through Echolocation. J Neurosci. 2017;37(6):1614-1627. doi:10.1523/JNEUROSCI.1566-12.2016

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Masks for Children During the COVID-19 Pandemic https://makermask.org/underserved-communities-masks-for-children/?utm_source=rss&utm_medium=rss&utm_campaign=underserved-communities-masks-for-children https://makermask.org/underserved-communities-masks-for-children/#comments Wed, 17 Jun 2020 22:44:17 +0000 https://makermask.org/?p=871 In this post Hope Metzler discusses masks for children including: six considerations for making and/or buying masks for children, information about when children should and should not wear masks, and an in depth look at the alternatives to masks for infants. This is part of a series of guest blog posts where we get a […]

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In this post Hope Metzler discusses masks for children including: six considerations for making and/or buying masks for children, information about when children should and should not wear masks, and an in depth look at the alternatives to masks for infants. This is part of a series of guest blog posts where we get a chance to hear voices and perspectives about making masks more accessible.

6 Considerations for Making or Buying Masks for Children

We all want the very best for our children, and that includes the masks that we make or buy during COVID-19.

Now that the initial rush to make simple, effective masks is over, makers are beginning to get very creative with their masks, often because our children are very vocal in their preferences for colors, action figures, favorite animals, popular characters, etc.  However, there are several considerations I encourage you to remember as you make or buy a mask for your child.

Two children wearing fabric masks diving the thumbs up

There is no one correct mask for every child. However, there are considerations that you should keep in mind:

1. Will Any Pattern Do?

The mask should be made from a pattern designed for children, so that there are not large gaps around the face.  Remember that time you put your child in an adult shirt and it was so cute?  The neckline dipped low, the armholes were huge and it hung down to their knees.  We want a mask that fits the child all around their face — nose to chin and from cheek to cheek.

Child wearing oversized t-shirt Masks for Children: Child wearing properly sized face mask with banjo bear print

2. Nose Wire or No Nose Wire?

This is an interesting debate.  Some schools that are preparing for reopening do not want the nose wire, which is understandable if the wire is removable or sharp. However, the nose wire is considered a critical piece of face masks:

  • To hold the mask in place while talking
  • To close the gaps around the nose
  • To prevent the child’s eye glasses from fogging up from their moist breath

I am a fan of the flexible closures used on 12 ounce bags of coffee.  They are two wires wide and covered in a plastic coating, almost like a tiny railroad track. Many makers cut the closure in half for a child’s mask.  And when sewn into the mask or into a channel along the nose, they become part of the mask and not something the child can pull out to use as a sword for a mini-fencing match.

Coffee bag, scissors, and bag closures for mask nose piece
Coffee closures make an excellent nose piece for face masks.

3. Ties or Ear Loops?

Most experts agree that young children should wear ear loops. Unlike ties which have a tendency to slip or come undone, the loops are placed behind the ears and do not move.  The concern with the ties relates to the same concern with anything tied around a child’s head.  Should the tie slip down while playing and become loose, the tie could get caught and become a strangulation hazard.  Children with glasses or hearing aides could use an extender behind the head.  Search for ear loop extenders for more examples.

Masks for children: View of mask from back with button ear loop extender
Ear loop extenders help to lift the loop off of the ear. This relieves pressure on the ears and makes room for hearing aides or glasses.

 

4. Beads to Make Ties or Loops Adjustable?

The use of beads on masks for children fall under the same guidance as small parts in toys for young children.  They are choking hazards because children love to put things in their mouths.  Think of it this way, children that are too young for small parts in toys, are too young for beads on their mask.

Back view of mask ties with bead adjuster
While beads might be used to make a tie or loop adjustable, they are not considered safe to be used on masks for small children.

 

5. Fabric?

It is recommended to have at least two layers of fabric. Ensure that the child can breathe comfortably for the length of time needed for your outing. The WHO recommends an inner layer of moisture absorbing fabric and an outer layer of water-resistant, nonwoven material, such as nonwoven polypropylene (NWPP) (see makermask.org/research for the science behind using NWPP). While adult masks often use more layers, young lungs may have a harder time breathing through thicker masks.

Fabric Masks for Children: Girl wearing a mask with dinosaurs on it

6. Can I Add Decorations?

The rule of thumb is to allow for breathing through the nose and mouth without restriction.  It is best to leave off applications, iron-on pictures, and any added decorations that block airflow in front of the nose and mouth.  Exceptions might be screen-printed fabrics, small details around the edges of the mask, or an application to the cheek.

Gluing on sequins, buttons and beads is not recommended for two reasons:

  1. We do not want kids breathing in any toxic fumes from the glue.
  2. Decorations could fall off and become choking hazards
Masks for Children: Dragon shaped novelty mask with extended face parts added to front of mask.
Added decoration or large parts on the front of a mask can reduce the breathability. These should be considered novelty masks and should only be used for home playtime.

Masks for Children: Additional Considerations

When Should Children Wear Masks?

Children should wear masks if they will be around other people, especially in cases where social distancing isn’t possible. As with adults, masks are not a substitution for social distancing or good hand hygiene.

Cincinnati Children’s Hospital provides a video for kids (below) as well as additional tips to help kids wear face masks (click here):

Is it OK for children have play dates now? According to Juan Dumois, M.D., a pediatric infectious diseases physician at Johns Hopkins All Children’s Hospital:

The pandemic has not ended, so any activities that involve close contact with other persons outside your family entail a risk of getting infected. Although most children are not getting as sick as adults with COVID-19, they can bring it home to the adults in the household who may be more likely to be hospitalized for it. With that said, it is still a good idea to have children minimize contact with other kids and conduct social distancing outside the home. If they will be around any other people, they should wear a mask. This is even more important in situations where social distancing isn’t possible.

What About Children with Special Health Concerns?

Although fabric masks are generally considered appropriate for children, the Academy of Pediatrics provides this advice about children with special health concerns:

Children who are considered high risk or severely immunocompromised are encouraged to wear an N95 mask to best protect themselves. Families of children at higher risk are encouraged to use a standard surgical mask if they are sick to prevent the spread of illness to others.

Face Coverings for Children during COVID-19 - Ideas to help children be less scared of masks.
Face Coverings for Children during COVID-19 – Ideas to help children be less scared of masks.

When should masks be avoided?

In general, the Center of Disease Control (CDC) says that people that cannot safely remove masks unassisted should not wear masks, but provides only one specific recommendation concerning children and masks, that they shouldn’t be worn by children under the age of 2. However, the Academy of Pediatrics provides guidance on three additional situations when children, regardless of age, should not wear masks. Summarized below, these recommendations suggest that children should not wear face masks:

  1. If they are under the age of 2 years, due to risk of suffocation
  2. If the only face covering available is a possible choking or strangulation hazard
  3. If the child has difficulty breathing with the face covering or is unconscious, incapacitated or otherwise unable to remove the cover without assistance.
  4. If wearing the face covering causes the child an increased risk of getting exposed to the virus because they are touching their face more often.

Masks for Children: DO NOT place a face covering on an infant or toddler age birth to 24 months old.

5 Reasons Why Infants Should Not Wear Masks

Many mask makers have very good intentions with making masks for infants and toddlers, but there are very good reasons why we do not want to cover an infant’s airway (mouth and nose) with cloth from 700 Children’s – A Blog by Pediatric Experts:

  1. Baby’s airways are smaller, so breathing through a mask is even harder on them.
  2. Using a mask on an infant may increase the risk of suffocation. Masks are harder to breathe through. A snug fit will give them less access to air, and a loose fit will not provide much protection.
  3. If the infant is having a hard time breathing, they are unable to take the mask off themselves and could suffocate.
  4. Older infants or young toddlers are not likely to keep the mask on and will likely try to remove it, as well as touch their face more.
  5. There are no N95 masks approved for young children.

An adult wearing a mask pushes a covered stroller down the street on Commonwealth Avenue in Boston during the coronavirus pandemic. JONATHAN WIGGS/GLOBE STAFF

7 Tips for Protecting Infants During COVID-19

Instead of using masks for infants, the American Academy of Pediatrics recommends placing infants in carriers, and then covering the carrier with a blanket:

If you must go outside or to a place where you are not able to practice social distancing with an infant, cover the car carrier with a blanket, which helps protect the baby but gives them the ability to breathe comfortably. Do not leave the blanket on the carrier in the car or at any time when the baby and carrier are not in direct view.

The Nationwide Children’s Hospital in Columbus, OH has more specific advice, suggesting 7 things you can do to help protect infants and children:

  1. Limit exposure and avoid unnecessary public contact.
  2. If going out is essential, cover the infant carrier (NOT THE INFANT) with a blanket, which helps protect the baby, but still gives them the ability to breathe comfortably. Do not leave the blanket on the carrier in the car or at any time when the baby and carrier are not in direct view.
  3. Keep your hands clean. Frequent hand washing with soap and water for 20 seconds is optimal, but hand sanitizer, with at least 60% alcohol is the next best substitute.
  4. Clean frequently-touched surfaces such as doorknobs, handles, light switches and electronics often.
  5. Teach older children to avoid touching their faces.
  6. If you cannot leave the young infant at home and you are pressed to go into the public, keep the outing short and always follow the 6 feet distancing rule.
  7. Remember to always wash your hands (and any siblings’ hands) as soon as you return home.

Masks for Children: Four Children wearing masks in a lin

Final Thoughts:

Making or buying a mask for a child can be fun!  There are so many exciting fabrics to choose from and most likely your child will want several choices.

Can they have a fun, crazy animal mask for play time?  Of course!

But when you are headed out the door to a place where social distancing will be difficult, then that is the time for the “outside” mask.

And leave our furry, novelty mask at home.

Illinois Chapter, American Academy of Pediatrics Infographic on Face Masks for Children. https://illinoisaap.org/

Edit (2020 August 27): For more information about masks for children, check with local, regional, and national guidance. Links to guidance from the CDC and the WHO are provided for your convenience below:

About the Author

Hope Metzler, M.Ed.

Hope graduated from the University of Maryland with a Masters in Special Education with a concentration in Early Childhood. She has been working with children for 30 years. As a military wife, she has moved around the world and has been a special needs consultant, training & curriculum specialist, special education teacher, and early interventionist. Her undergraduate work included deaf education and she is fluent in American Sign Language.

 

Additional Resource Topics From Around the Internet

Research Articles

  • Esposito, S., & Principi, N. (2020). To mask or not to mask children to overcome COVID-19. European journal of pediatrics, 1–4. Advance online publication. https://doi.org/10.1007/s00431-020-03674-9

 

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WHO Guidance on Face Masks Changes https://makermask.org/who-guidance-on-fabric-masks/?utm_source=rss&utm_medium=rss&utm_campaign=who-guidance-on-fabric-masks https://makermask.org/who-guidance-on-fabric-masks/#comments Sat, 06 Jun 2020 11:46:38 +0000 https://makermask.org/?p=814 Surprising New Guidance from the WHO The WHO guidance on face masks for COVID-19 has changed to include the recommendation that the general public use fabric masks in public settings where physical distancing can’t be achieved and provides specific guidance on mask layers and materials. According to the World Health Organization (WHO), the ideal fabric […]

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Surprising New Guidance from the WHO

The WHO guidance on face masks for COVID-19 has changed to include the recommendation that the general public use fabric masks in public settings where physical distancing can’t be achieved and provides specific guidance on mask layers and materials. According to the World Health Organization (WHO), the ideal fabric mask for use by the general public consists of three layers, where two of the three layers are water-resistant (hydrophobic) materials such as polypropylene, and the third layer in contact with the face is an absorbent (hydrophilic) material such as cotton. Dr. Maria van Kerkhove, a WHO epidemiologist stated on June 5, 2020 that,

With those three layers, and in that combination, that fabric can actually provide a mechanistic barrier that if someone were infected with COVID-19, it could prevent those droplets going through and infecting someone else.

In this post we highlight key points pulled straight from yesterday’s guidance (click here for the full WHO June 5, 2020 guidance) that we wanted to share immediately. Stay tuned! A more in depth review and commentary is underway…

[Update August 2020] An overview of the WHO Guidance on Masks for Children has been added (click here for the August 21, 2020 WHO Advice on Masks for Children)

Key points from the new WHO guidance:

Fabric masks are defined as masks made from woven and non-woven fabrics.

Non-medical (also referred to as “fabric” in this document) masks are made from a variety of woven and non-woven fabrics, such as polypropylene.

Use of fabric masks is encouraged in public settings where physical distancing cannot be achieved, especially enclosed spaces such as grocery stores, schools, churches, mosques, buses, planes, and trains.

“WHO has updated its guidance to advise that to prevent COVID-19 transmission effectively in areas of community transmission, governments should encourage the general public to wear masks in specific situations and settings as part of a comprehensive approach to suppress SARS-CoV-2 transmission.”

Situations where the general public should be encouraged to use fabric masks

from: WHO Advice on the use of masks in the context of COVID-19, June 5, 2020

Situations

Populations

Areas with known or suspected widespread transmission and limited or no capacity to implement other containment measures such as physical distancing, contact tracing, appropriate testing, isolation and care for suspected and confirmed cases. General population in public settings such as grocery stores, at work, social gatherings, mass gatherings, closed settings, including schools, churches, mosques, etc.
Settings with high population density where physical distancing cannot be achieved; surveillance and testing capacity, and isolation and quarantine facilities are limited. People living in cramped conditions and specific settingssuch as refugee camps, camp-like settings, slums.
Settings where a physical distancing cannot be achieved (close contact). General public on transportation (e.g. on a bus, plane, trains)
Specific working conditions which places the employee in close contact or potential close contact with others e.g. social workers, cashiers, servers.

The ideal combination of materials for fabric masks include 3-layers with a water-resistant (hydrophobic) outermost layer. 

The ideal combination of material for non-medical masks should include three layers as follows:

  1. an innermost layer of a hydrophilic material (e.g. cotton or cotton blends);
  2. an outermost layer made of hydrophobic material (e.g., polypropylene, polyester, or their blends) which may limit external contamination from penetration through to the wearer’s nose and mouth;
  3. a middle hydrophobic layer of synthetic non-woven material such as polypropylene or a cotton layer which may enhance filtration or retain droplets.

Nonwoven spunbond layers offer adequate filtration and breathability.

Recent data indicate that two non-woven spunbond layers, the same material used for the external layers of disposable medical masks, offer adequate filtration and breathability. Commercial cotton fabric masks are in general very breathable but offer lower filtration. The filter quality factor known as “Q” is a commonly used filtration quality factor; it is a function of filtration efficiency (filtration) and breathability, with higher values indicating better overall efficiency.

 

The new data in the WHO guidance about the benefits of hydrophobic fabric mask materials like nonwoven polypropylene comes from Zhao et al (published June 2, 2020). They evaluated the filtration efficiency and breathability of common household materials used in masks (cotton, silk, nylon, polyester and polypropylene) and found that hydrophobic materials like spunbond nonwoven polypropylene had better overall performance than cotton. Not only that, unlike absorbent materials, the hydrophobic materials we able to hold an electrical charge (static electricity from rubbing the NWPP on latex or nitrile gloves for 30 seconds), which boosted their performance even further! At room temperature the boost in particle filtration from static electricity lasted overnight and at body temperature and high humidities the effect lasted over an hour!!!
Figure 1. Adapted from Zhao et al 2020. The full article is available at: https://pubs.acs.org/doi/pdf/10.1021/acs.nanolett.0c02211

Masks made with spunbond nonwoven polypropylene and cotton may be boiled or steamed.

Non-woven polypropylene (PP) spunbond may be washed at high temperatures, up to 125°C. Natural fibres may resist high temperature washes and ironing. Wash the mask delicately (without too much friction, stretching or wringing) if nonwoven materials (e.g. spunbond) are used. The combination of non-woven PP spunbond and cotton can tolerate high temperatures; masks made of these combinations may be steamed or boiled… Where hot water is not available, wash mask with soap/detergent at room temperature water, followed by either

  1. boiling mask for one minute OR
  2. soak mask in 0.1% chlorine for one minute then thoroughly rinse mask with room temperature water, to avoid any toxic residual of chlorine.

Caution: Do not use elastic material for masks.

It is preferable not to select elastic material for making masks; during wear, the mask material may be stretched over the face, resulting in increased pore size and lower filtration efficiency throughout use. Also, elastic materials may degrade over time and are sensitive to washing at high temperatures.

Masks should be handled carefully and washed frequently.

Masks should only be used by one person and should not be shared. All masks should be changed if wet or visibly soiled; a wet mask should not be worn for an extended period of time. Remove the mask without touching the front of the mask, do not touch the eyes or mouth after mask removal. Either discard the mask or place it in a sealable bag where it is kept until it can be washed and cleaned. Perform hand hygiene immediately afterwards. Non-medical masks should be washed frequently and handled carefully, so as not to contaminate other items. If the layers of fabrics look noticeably worn out, discard the mask.

Guidance and practical considerations for fabric mask production and management

from: WHO Advice on the use of masks in the context of COVID-19, June 5, 2020

Fabric Selection:

  • Choose materials that capture particles and droplets but remain easy to breathe through
  • Avoid stretchy material for making masks as they provide lower filtration efficiency during use and are sensitive to washing at high temperatures
  • Fabrics that can support high temperatures (60oC or more) are preferable

Construction:

  • A minimum of three layers is required, depending on the fabric used: an inner layer touching the mouth and an outer layer that is exposed to the environment.
  • Choose water absorbing (hydrophilic) materials or fabric for the internal layers, to readily absorb droplets, combined with an external synthetic material that does not easily absorb liquid (hydrophobic).

Mask management:

  • Masks should only be used by one person.
  • All masks should be changed if soiled or wet; a soiled or wet mask should not be worn for an extended period of time.
  • Non-medical masks should be washed frequently and handled carefully, so as not to contaminate other items.
  • Clothing fabrics used to make masks should be checked for the highest permitted washing temperature, which is indicated on the clothing label.
  • Non-woven polypropylene (PP) spunbond may be washed at a high temperature, up to 140oC.
  • The combination of non-woven PP spunbond and cotton can tolerate high temperatures; masks made of these combinations may be steamed or boiled.
  • Where hot water is not available, wash mask with soap/detergent at room temperature water, followed by either i) boiling mask for one minute, or ii) soak mask in 0.1% chlorine for one minute and then throroughly rinse mask to avoid any toxic residual of chlorine.

WHO Guidance for How To Wear a Fabric Mask Safely: The Do's.

The WHO Guidance on how to wear a fabric mask: The DON'Ts

WHO Advice on Masks for Children (Update August 2020)

When it comes to important design considerations for masks for children, the WHO advice simply states that,

“The design of face masks for children should take into consideration the overall quality of the fabric, suitable breathability and comfort” and child-friendliness (appropriate size, colours, design, etc.) to help improve their acceptance of and use by children.”

However, the WHO provides more detailed advice about mask use among different age-groups:

Age

WHO Advice on Masks for Children  (August 21, 2020)

< 5 Children < 5 should not wear masks for source control “Based on the expert opinion gathered through online meetings and consultative processes, children aged up to five years should not wear masks for source control. This advice is motivated by a “do no harm” approach… The rationale included  consideration  of  the  fact  that  by  the  age  of five  years,  children  usually  achieve  significant  developmental milestones, including the manual dexterity and fine motor coordination movements needed to appropriately use a mask with minimal assistance.”
6 – 11 May be Recommended In Some Situations “For children between six and 11 years of age, a risk-based approach should be applied to the decision to use of a mask. This approach should take into consideration: 1) intensity of transmission in the area where the child is…; 2) social and cultural environment…; 3) the child’s capacity to comply with the appropriate use of masks and availability of appropriate adult supervision; 4) potential impact of mask wearing on learning and psychosocial development; and 5) additional specific considerations and adaptions for specific settings.”
> 12 Follow Mask Advice for Adults “WHO and UNICEF advise that children aged 12 and over should wear a mask under the same conditions as adults, in particular when they cannot guarantee at least a 1-metre distance from others and there is widespread transmission in the area.”

It is important to note that this guidance is different than the guidance currently provided by the CDC, which advises the use of masks for children over the age of two when social distancing isn’t possible.

CDC Advice for Children > 2

(July 21, 2020)

WHO Advice for Children < 5

(August 21, 2020)

Children 2 years and older should wear a mask over their nose and mouth when in public settings where it’s difficult to practice social distancing. This is an additional public health measure people should take to reduce the spread of COVID-19 in addition to (not instead of) the other everyday preventive actions.”  “Based  on  the  do  no  harm  approach,  if  the  lower  age  cut-off  of  two  or  three  years  of  age  is  to  be  used  for  recommending  mask  use  for  children,  appropriate  and  consistent  supervision,  including  direct  line  of  sight  supervision  by  a  competent adult… This is both to ensure correct use of the mask and to prevent any potential harm associated with mask wearing to the child.”

Additional Links/Information

Check appropriate regulatory agencies for local, regional, and national guidance.

For More Information about Mask Designs Considerations for Children Check Out:

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