Originally Posted by grann of 6
I would prewash all the fabric first, though, when mixing fabrics so that any shrinkage is out of the way before assembly of the quilt.
This is good advice. I always prewash for another reason, as well: If the fabric is 'wonky' or out of shape on the bolt, it will straighten in the wash. Then cut pieces do not change shape after washing, especially if the pieces are larger.