Materials

  • Plain woven cotton, at least 100 threads per inch

  • Flannel, either cotton or poly-cotton blend, at least 90 threads per inch

  • Tea towel material

  • Heavy, good quality, cotton T shirt material

  • At least one layer of non-woven industry-grade spunbond polypropylene, recommended by Health Canada and the WHO.  

​With fabric that stretches, such as any knit, for example, T shirt fabric, use a design with edge stitching to prevent the cloth being stretched when worn, which will increase the size of gaps in the material and affect filtration.  

Layers

  • 3 or 4 layers 

  • Combine cotton/flannel against the face with polypropylene for middle or middle and outer layers.

  • If you have a pocket mask that doesn't contain sewn-in polypropylene, don’t use a disposable filter, instead use a rectangle of washable polypropylene.

 

There is a trade-off with increased layers: they provide increased filtration efficiency, but also increase the resistance to breathing, which may lead to discomfort. Increased resistance with increased layers also leads to increased leak around the edges, decreasing the efficiency of the mask.

Here's a link to our longer article, How Can Cloth Stop a Tiny Virus?