I prewash and have found even some expensive batiks bleed and bleed and bleed. So, no more of those for me. For Father's Day, bought my husband two pairs of jeans (what he needed, not wanted) and could see that they probably should be prewashed. He was amazed at all the color that came out on the Color Catcher! We washed them twice and the Color Catcher picked up dye both times.