Originally Posted by babalu
I don't prewash jelly roll or charms, but I do wash and dry fat quarters. One quilt store owner told me that it's fine to mix prewashed with unwashed, because there isn't as much shrinkage in fabrics as there once was (thus the switch from 45" wide to 42"). I've never had a problem combining the two! Good luck!
I'm not sure if that's the exact reason for the switch from 45" to 42" but there are fabrics that I would not mix because they shrink a lot more than others. JMHO.