MakerMask

3 Easy DIY Mask Tests

Photo: DIY Mask Testing Setup for Fabric Materials. Photo includes spunbond nonwoven polypropylene mask, teaspoons, scale, elastic band glass, and cotton ball

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.

 

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.

 

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.
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

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:

3 Easy DIY Mask Tests

45 thoughts on “3 Easy DIY Mask Tests

  1. I would strongly recommend to first decide on a cleaning method, then apply that method to the fabrics you want to test and only after having done that: do the tests!
    Why? Because I found out none of the polypropylene that I could get in The Netherlands (be it bought by the meter, packed as squares or as reusable shopping bags) was still water-repellent/ hydrophobic after washing it. Really none of them! I asked people in other countries to follow my working order: same results!
    So: apply cleaning method to test samples first, then test! Otherwise basically your test results are useless!

    1. I recommend cleaning/disinfecting all materials before working with them. What cleaning methods are you using? I saw your photos over in the OSMS threads. For the most part I boil or steam. I see decreased water resistance with repeated disinfection cycles, but the difference doesn’t seem to be as dramatic as what you are seeing. I’m also wondering if the new procedure using lower temperatures and less moisture saturation (putting the mask in a paper bag and using moist heat 65C/150F for 30 minutes in a multicooker) helps preserve the water resistance for more cycles.

  2. Pingback: Spirit Self Health
  3. Dear Reader,
    Thank you for the wide collection of information for use by those of us sewing masks. The 7 inch x 9 inch pleated mask we currently make and use has a layer of high-count cotton nearest the skin, followed by two layers of polyester charmeuse, and a top (exterior) layer of a light-weight water-repelling polypropylene material (GSM unknown). It is readily breathable. Would this 4-layer mask likely succeed as appropriate to wear in public?
    Sincerely,
    Sstephen Baig

  4. Hello there! I could have sworn I’ve visited your blog before but after
    looking at a few of the articles I realized it’s new to me.

    Regardless, I’m definitely pleased I found it and I’ll be book-marking it and checking back often!

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