I always pre wash. Same reason as most that do. However my washing machine does not have a gentle cycle so I fill the machine using regular cycle for a very short time. :idea: With long lengths of fabric, not on the selvage edge, but the cut edges I sew across with a fine stitch before washing. This keeps the raw edges from unraveling during the wash cycle. Then I also have poured water into my clean bathtub with liquid gentle laundry soap, swished it around a lot, put the fabric in the washer to spin, swish the fabric in clean water and back to the washer to spin. Small pieces, ie: half yards are hung on a drying rack. Extra work, but saves the fabric. Sorry about the duplicate message. :-(