I mostly use inexpensive sheets that are 80%cotton with 20% polyester, and find them excellent to use, and feel lovely and soft. I have quilted using a tougher 60% poly sheet and it was awful, with no give and it kept skipping stitches. Mytwo-needle coverstitch machine won't sew that fabric at all, it's like parachute fabric. Had a call from the owner of that quilt last night. She washed the quilt and found the poly backing is pilling, so now is wanting it replaced, or covered up.