I also use the shout color catchers when I prewash my fabrics. I was shocked how much some of the fabrics bleed.
Also I even wash my fat quarters. I use those knit zipper bags that you use for fine fabrics undies etc. It's great because they don't all tangle up in knots.
I use the color catchers in almost every load of wash since a long time ago I turned my husbands underware Pink. He wasn't to happy. Also if you can hang your fabric on a clothes line to dry it is alot easier to iron. Kathy kjym