I prewash all my fabrics because all the chemicals that are in them give me problems. As a result, my fabrics are floppy. I spray starch them so they are very stiff - that way even if I am cutting on the bias there is no movement when I piece and very little when I quilt. Since I mostly use an accuquilt die cut machine, the stiff also means nothing moves when I cut and if the grain is a bit off it doesn't matter.