I have done alot of prewashing by hand in a large white sink, and you'd be surprised how many fabrics bleed, both from quilt shops and big box stores. There isn't a color out there that I haven't witnessed bleed. The white sink and smaller amount of water, as compared to a full washing machine, really show up the bleeding. I use the hottest water I can get out of the tap and rinse until the water is clear or nearly so.