A recent study testing the effectiveness of cloth masks made with a variety of fabrics found that adding 2 layers of natural silk, 2 layers of 90% poly/10% spandex chiffon or one layer of 65% cotton/35% poly flannel to a high thread count cotton mask resulted in protection that is only “slightly inferior to the N95 mask above 300 nm, but superior for particles smaller than 300 nm.”
The study also found that a “quilt, a commonly available household material, with a fibrous cotton batting also provided excellent filtration across the range of particle sizes (>80% for <300 nm and >90% for >300 nm).”
Why it Works
The study authors explain that the silk, poly chiffon and flannel are electrostatically charged which causes them to attract small droplets.
Cotton, meanwhile, provides a mechanical barrier to droplets. Combining a high thread count cotton with an electrostatic fabric creates a hybrid mask that is more effective than either fabric alone:
“Combining layers to form hybrid masks, leveraging mechanical and electrostatic filtering may be an effective approach. This could include high thread count cotton combined with two layers of natural silk or chiffon, for instance.”
Avoid Poly Satin and Synthetic (Poly) Silk as well as Low Thread-Per-Inch Cotton
The scientists tested “the performance of over 15 natural and synthetic fabrics. They report that “[s]everal fabrics were tested that did not provide strong filtration protection (<30%), and examples include [97% polyester and 3% Spandex] satin and synthetic [100% polyester] silk.”
They also noted that low thread count cottons do not provide as good a mechanical barrier to droplets as higher thread count cottons. In their tests, “a 600 TPI cotton [sheet] performed better than an 80 TPI [quilter’s] cotton” and they recommend that “[f]abrics that are porous should be avoided.”
A Good Fit is Essential
The study found that having a good fit with little to no leakage is essential for effective protection, noting that “gaps between the contour of the face and the mask as caused by an improper fit will affect the efficiency of any face mask.” In their tests, they found that leakage can reduce the effectiveness of a mask by over 60%.
Our initial foray into mask making was to make N95 mask coverings that we donated to Johns Hopkins Hospital using a specific mask shape requested by the hospital:
While we’re continuing to make and donate masks for medical workers, based on the recent study, we’ve started experimenting with masks that have two layers of natural silk sandwiched between two layers of cotton, a placket over the nose to hold a removable wire allowing for better fit, and a filter compartment.
We’ve also been playing around with different (and more comfortable) ways to hold a mask in place other than with elastic or cloth ties. We thought it would be fun to share what we’ve come up with so far.
In this design, the straps are stretchy, but fixed and not adjustable.
In this design, the lower jersey straps tie. The upper is like a headband.
Feel free to leave your comments! Once we’ve finalized our designs, we’ll be offering limited quantities of our masks for sale. And as we learn more about research into cloth mask materials and designs, we'll keep you posted.
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In order to help you estimate the fit you want, we list our model's measurements and the size she is wearing below each photo or under "Specs" on the product page.
Note: "Hip" = Lower hip/largest point of hip
XX-LARGE / 2X