Fabrics have a sizing on them, so I usually wash all fabrics before cutting and sewing. Except if using charms or jelly rolls. To test a fabric, take a piece of white cloth dampened and rub on the fabric. If the color comes off, it will probably run. Then I use the vinegar and salt method to set the color. What is "color catcher"? I've never heard of that and where does one find it?