I ALWAYS prewash...no surprises. When I wash the fabric I clip the corners so when I go in my stash I know that it's been washed. When I first started sewing I made a blouse and it was beautiful.....until I washed it. So when I started quilting I always washed because I hand dye a lot of fabric and don't want to cry after I do all that work and it bleeds anyway. Even if I used retayne.