New WHO and Health Canada recommendations not recommend a three layer mask with one layer of polypropylene material and two layers of tightly woven material such as cotton.
Choices for Tightly Woven Cotton
This is by far the most popular fabric for mask making. It is readily available, durable, washable, and comes in a huge variety of prints. This is an excellent easy to sew choice.
Poplin is usually sold for shirts and other apparel. It is usually slightly higher thread count but made with finer threads making it a bit softer and more breathable then quilting cotton.
Cotton shirting is a plain weave fabric similar to quilting cotton except it is a little bit lighter weight. While quilting cotton is usually 140-160 grams per square meter shirting is usually 100-120 grams per square meter. Shirting is also sometimes higher thread count but not always.
Sheeting is similar again to quilting cotton, the only difference is usually in thread count which is sometimes higher. I do not recommend using sheeting with a thread count over 300 as it's not possible to breath through such a densely woven fabric. Using a higher thread count specifically violates the recommendations by health Canada.
Lawn is a very finely woven fabric, it always has a very high thread count and is woven with very fine threads making it very light weight / semi-sheer. This makes it one of the softest fabrics and makes excellent soft mask lining.
Chambray is often worn like denim and is also woven with a white weft for contrast. Unlike denim, which would be far too heavy for a mask, chambray is fairly light weight and can give you mask the "denim" look.
Find out cottons for masks here: https://riversidetextiles.ca/collections/mask-fabric
Choices for Polypropylene / Filter Layer
Basic polypropylene can be washed and sewn directly into your mask. However caution should still be used when putting heat near polypropylene fabric. They generally cannot be ironed as this fabric has a low melting point.
Not all polypropylene is washable either. There is significant concern around people using melt-blown polypropylene which degrades quickly and of which small fibres can easily be inhaled and embedded in wearers lungs. Always use spunbound polypropylene that is labelled as washable. More informations can be found here.
Filti is a filtration material that has provided a level of filtration comparable to n95 material. It is a base layer of spunbound polypropylene with a nanofiber filtration layer on top. This material is best as a filter or as a short term mask that is sterilized in the oven between uses until it becomes visibly soiled. This is because the nano-fiber layer can be damaged by the washing machine. Filters can be inserted into masks and re-used until they become soiled by sterilizing in the oven.
Our filtering layer materials can be found here: https://riversidetextiles.ca/collections/mask-filter-material