I wash everything before i use it in a quilt. If it is going to shrink or the color run, I want that to happen before I put it in a quilt. Some batiks need to be treated with Synthropal. It hellps to set the dye so it doesn't run anymore. I find that dark colors like purple or navy tend to run and some reds do too. I was always told the rule is wash all or none of your fabrics in a quilt.