With masks sold out during the coronavirus outbreak, many people will have to make do with what scientists claim is “the last resort”: the DIY face mask.

Data shows that DIY and homemade masks are effective at capturing viruses. But if forced to make our own mask, what material is best suited to make a mask? As the coronavirus spread around China, netizens reported making masks with tissue paper, kitchen towels, cotton clothing, and even oranges at times!

The Best Material for Making a Homemade DIY Mask

Researchers at Cambridge University tested a wide range of household materials for homemade masks. They tested how well these materials could capture virus-sized particles in comparison to a surgical mask. They shot Bacillus atrophaeus bacteria (0.93-1.25 microns in size), and Bacteriophage MS virus (0.023 microns in size) at different materials to see how well they coped.Effectiveness of household materials at making DIY homemade masks

Not surprisingly, the surgical mask performed best, capturing 97% of the 1-micron bacteria. Yet every single material filtered out at least 50% of particles. The top performers were the vacuum cleaner bag (95%), the tea towel (83%), the cotton blend shirt mix (74%), and the 100% cotton shirt (69%).

Homemade Masks vs. Viruses

That test used bacteria that were 1 micron large, yet the coronavirus is just 0.1 microns – ten times smaller. Can homemade masks capture smaller virus particles? To answer this question, the scientists tested 0.2 micron Bacteriophage MS2 particles.

On average, the homemade masks captured 7% fewer virus particles than the larger bacteria particles. However, all of the homemade materials managed to capture 50% of virus particles or more (with the exception of the scarf at 49%).

Are Two-Layered Masks More Effective?

If the problem is filtration effectiveness, would the masks work better if we made two layers? The scientists tested virus-size particles against double-layered versions of the tea towel, pillow case, and 100% cotton shirt.

Overall, the double layers didn’t help much. The double-layer pillowcase captured the same amount of particles, and the double-layer shirt captured just 2% more particles. Yet the extra tea cloth layer boosted performance by 14%. That made the tea towel as effective as the surgical mask.

This data shows the tea towel and vacuum cleaner bag are the best materials for capturing particles. You may therefore think that these materials are best for making DIY masks. But the researchers came to a different conclusion.

The researchers concluded that the best materials for a homemade face mask are the pillowcase and the 100% cotton t-shirt. Why?

Don’t Forget Mask Breathability

The answer lies in breathability. In addition to particle effectiveness, the researchers tested the pressure drop across the fabric. In other words, how easy it is to breathe through the fabric? They compared breathability to the breathability of the surgical mask.

Although the tea towel and the vacuum bag captured the most particles, they were also the hardest to breath through. With two layers, the tea towel was over twice as hard to breathe through as the surgical mask. In contrast, the pillow case, t-shirt, scarf, and linen were all easier to breathe through than the surgical mask.

Researchers’ Pick for Best-Performing Homemade Mask Material

Based on particle capture and breathability, the researchers concluded that cotton t-shirts and pillow cases are the best choices for DIY masks.

Are there any other materials we can use? The Cambridge researchers left out one common material: paper towel. Read more about how well paper towel masks can capture particles in our follow up blog post.

Bottom line on making DIY masks with household materials

Test data shows that the best choices for DIY masks are cotton t-shirts, pillowcases, or other cotton materials. These materials are able to filter out approximately 50% of 0.2 micron particles, similar in size to the coronavirus. They are also as easy to breathe through as a surgical mask, which makes them more comfortable enough to wear for several hours.

Doubling the layers of material for your DIY mask gives a very small increase in filtration effectiveness, but makes the mask much more difficult to breathe through.

Read more on DIY masks:

Still not sure if DIY masks really work? See the real-world test data on the effectiveness of homemade DIY masks to find the answer.

Are you already convinced that DIY masks work? Then learn how to make a DIY mask here [coming soon!]

Paddy graduated in aeronautical engineering from Bristol University, and now runs Smart Air’s operations from Beijing. He’s an advocate for open data, free information and transparent business.

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This content was originally published here.

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