I don't pre-wash my fabrics. It was always too much work to wash and then press the fabric. I live in apt complex now so I don't have the convenience of a W/D. I do pre-check my darker reds, blues and purple and only had a problem with one dark navy. I prefer the starch already on the fabric when piecing. I have read and heard that you are not suppose to wash charms or jelly roils because you won't have the size or width after drying.