I have used Retayne since 2002 when I discovered it It is a wonderful product that prevents me from worrying that I will give someone a quilt, runner or even a potholder that runs into itself, or into other items that the recipient washes it with. Even Alex Anderson stated in one of her shows that her non-prewashed fabrics ran in the wash, and she had to seek expert help to restore her quilt. I highly recommend it.
I've used Retayne for many years to prewash all dark colors, such as reds, greens, blues and black, as well as any prints that contain dark colors. It prevents the colors from bleeding into surrounding fabrics. Well worth doing. Followthe directions carefully!