I sew a lot with batiks and so do the gals in my friendship group. None of us prewash, but we do use a Color Catcher in the washer when we wash them the first time or two. So, I always wash them before I give them away to ensure a Color Catcher is used. I just made a quilt with lots of dark batiks and white batik for the sashing. No bleeding at all when washed with the Color Catcher. I don't know if it would have bled without the Color Catcher, but I sure don't want to take any chances after all the work that goes into a quilt. Don't worry. I always keep Color Catchers in the laundry room. They really do their job!!!