Heid

I probably wouldn't pre-wash charms or jelly rolls because you lose the edges of fabric when they are washed. But when i get fabric scraps to do paper piecing projects, I usually throw them into a lingerie bag and wash them with the rest of my fabrics (and a color catcher). If not all materials in a project are pre-washed, you could have an issue with the non-prewashed fabrics shrinking while the pre-washed ones don't, but hopefully it wouldn't be a noticeable difference. Have fun quilting!