Look what Kevin did for me! Such a nice boy. He cut a huge stack of filter fabric, and a huge stack of muslin, enough to get me through the August mask orders.
I used to use printed fabric on front and back of the masks, and then at some point I realized that a) muslin was softer against your skin, and b) muslin was notably less expensive too.
Muslin backs maybe don’t give quite as polished and crisp a look, coming out of the package, but I think they actually make for better masks overall.