Here are the instructions for a better-fitting homemade mask that can filter particles 2x better than cotton created by three clothing designers

Three fashion designers have created a new homemade, surgical-style mask and are giving the pattern away for free.

Their design includes a pocket that can be filled with a material to help the mask filter tiny particles better than a mask made only from cotton, according some testing that they did.

After testing dozens of materials with rented particle-testing equipment, they discovered that certain blue shop towels, as well as a certain white industrial cloth, can help a homemade cotton surgical mask filter particles 2-to-3x better than cotton. 

Their testing also showed that the fit of the mask was crucial to having it filter particles well.

So they designed a new mask for the legions of home sewers making masks right now.

This is not an FDA-approved N95 mask but is intended to be a better-fitting alternative to some of the other patterns for surgical masks circulating on the internet.

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Three fashion designers created a homemade, surgical-style mask that can filter particles better than a typical cotton mask, according to their home particle testing, and they're now giving away the pattern and instructions for free.

Their new design uses a cotton shell and allows the sewer to add another layer into the mask to act as a filter, either by sewing the filter as a lining or by adding a pocket into the mask and putting the filter material into the pocket.

The designers spent days testing dozens of materials and found that polyester hydro-knit, found in certain brands of blue shop towels, worked best, and could filter particles twice as well as cotton. They also found that a fabric called polypropylene, used in a certain type of white, oil-absorbing shop towel, works well too.

Business Insider originally wrote about this project earlier this month and the designers — Lindsay Medoff, the CEO of boutique Los Angeles clothing manufacturer Suay Sew Shop, along with her business partner, Heather Pavlu, and her best friend from high school, Chloe Schempf — have since received an outpouring of support for their project, they say.

They have now posted instructions and the pattern as a downloadable PDF on Suay's and Schempf's GoFundMe pages (which are raising money for professional mask making in LA and Michigan respectively).

The designers created the mask after testing dozens of fabrics with particle-testing machines that check for particles as small 0.3 microns. The coronavirus that causes COVID-19 is smaller than that. However, the CDC is recommending that everyone wear some sort of mask in public, even a bandana, to help stop the spread of the disease, since any face mouth covering can block droplets that could carry the virus. The designers' goal was to find fabrics that people could buy as easily as cotton and that balanced filtration with breathability.

After testing everything from vacuum cleaning bags to commercial fabrics, Medoff, Pavlu, and Schempf discovered that stretchy blue shop towels made from polyester hydro-knit seemed to meet many of their criteria. It should be noted that this is not an FDA-approved N95 mask but is intended to be a better-fitting alternative to some of the other patterns for surgical masks circulating on the internet. (For the full details on how they went about their testing, read the original story: Using blue shop towels in homemade face masks can filter particles 2x to 3x better than cotton, 3 clothing designers discover after testing dozens of fabrics.)

Some experts are concerned that wearing unusual materials directly on your mouth as a mask could cause skin irritation or cause tiny particles of the material to be inhaled. That's why, in their latest design, Medoff, Pavlu, and Schempf created two versions of the mask.  

One version sews a filter lining directly into the mask. The second version adds a separate pocket for filtering materials. That designs allows someone to use a shop towel for filtration without putting it in direct contact with their face. The masks with a pocket can also be hand-washed and line-dried, while the masks with a filter lining cannot. 

By adding a pocket to the tight-woven cotton mask and putting in two layers of shop towels, their tests showed the mask consistently filtering out 82% of particles, although some of their tests showed it filtering at an even higher level. Filtering depends on many factors, including the mask's fit on the person.

To improve fit, their design includes a wire nose piece that keeps the mask snugly in place, elastic trim, and other sewing techniques. So, even those who don't want to add a filter to the mask may want to use this homemade mask design for its fit.

The materials the designers recommend for their mask design are:

Tight-woven cotton like quilter's cotton, tight woven muslin, or old twill pants to make the mask's shell. 

For the optional filter, the designers had the best test results with these three brands: Wypall X80 Towel, Zep Shop Towel, Toolbox Shop Towel. It's worth noting that the makers of the shop towels have not approved their towels to be used as masks, do not warranty masks made from them, nor do they recommend that their towels be used as a mask.

They also tested the Scott Shop Towel brand and while it worked better than no filter, it didn't work as well as the other mentioned brands (it filtered out 70% of particles versus 82%) 

Another option for a filter is the oil absorbent towels that Suay, a commercial clothing company, was able to buy in bulk, though it's not as easily obtained by the public. 

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