I have prewashed a few batiks. noticed while makeing a test block that one of them bled on my ironing board so i did prewash the rest. and i wound up prewashing about a 4 yard cut last week. not because i wanted too...... but it turns out that leaving your spray basting on your ironing pad where your starch usually is........well. not a good thing, and i do tend to starch heavily. lol. got a nice clean iron also.