THERE'S A REASON OUR MASKS ARE MADE WITH 100% WOVEN COTTON
The studies are plentiful. From effectiveness and breathability to "maskne", the results are clear that a woven cotton fabric is your best bet for a reusable mask.
Studies show that knit fabrics (polyester is a knit) perform poorly when used for face masks. Knits (stretchy, think polyester and performance fabrics) are often the type of mask offered by promotional product companies. It is also more likely to give you “maskne” (see that study below). A woven cotton performed at the top of the list, next to an N95:
Polyester is also a synthetic, which makes it doubly worse:
The following is a long study on face mask effectiveness. If you go to the end of the study, you will see again that a stitched cotton mask is at the top of the list for best results:
Knits are also culprits for “maskne” (acne from wearing face masks, because of the humidity that gets built up in the masks). Cotton is one of the best choices to prevent maskne due to its breathability:
And whatever you do, do not choose a face mask with an air vent. The CDC has noted that air vents should NOT be used in masks: