I prewashed some blacks the other day and they ran a lot, color catchers were not the answer. I put the fabrics in a large sink with hot water and Retayne, then rinsed in cold, and that solved the problem. I did the same with a red and white finished quilt in the bathtub, since the red was running, and I had washed it several times before I put it in the quilt. Retayne in the tub might be the way to go if you are concerned.