I've always been a pre-washer because I want to check to make sure colors won't run and that everything is preshrunk. I made a scrap quilt recently using prewashed reds, and still had some run. Fortunately, the blue Dawn worked to remove the red color run on my white background. But now I buy Retayne in large amounts and pretreat every fabric which shows any likelihood of running. It's not cheap, but it's well worth it to me to know my quilt (that I've poured time and effort into) won't be ruined when washed by either me or a recipient. It also doesn't take a lot of Retayne to treat a fabric. Color catchers don't set dyes, so I find them of very little use, other than to show me that a fabric's dyes are not set when washing. Blues, reds, purples, and greens seem to be the worst offenders, but I also had a light yellow run. The price of the fabric doesn't ensure that the dyes won't run.