I often will throw in a half color catcher in the second rinse. If the whole color catcher has picked up a lot of the color in the wash & first rinse, the second rinse sheet often comes out white. Then I know the fabric won't bleed anymore. Sometimes the half sheet will pick up some color. Then I'll rinse again with another half sheet and hopefully that one will stay white. If not, then I have a big decision whether to use that fabric in a quilt.