I prewashed some fabric just last night. I had one fabric with a black background. I put it in a tub of water to see if it ran. Didn't think it did. Put it in with the rest of the fabric I was washing. A dark pink fabric appeared to run in the tub test, so I soaked it with water and Retayne. When I took the other fabric out of the dryer, I noticed that the fabric with the black background had bled a steak on some light pink fabric. Thank goodness it was only a small streak on only one part. None of the other fabric was bothered. I have enough fabric that I can cut out the streak and still have enough for my quilt. I will be soaking the black fabric with Retayne before I use it, however. I expect all my quilts to be washed, and I wash them myself before I give them away. I don't like bad surprises, and I actually think this saves me time, rather than wastes it.