I prewash all material including jelly rolls. I have found that if I take 4-5 strips and tack them in a few places, on the each end and a couple in the middle then throw them into a lingerie bag or old pair of panty hose, they don't tangle and fray so much. Panty hose are great because you can tie them off. I've done this with scraps that may have a musty odor from sitting too long. if I get material from others I always prewash.