They make special products to remove that stuff from your iron, but I found a tip once (I think in Love of Quilting) about using dryer sheets & have been using them ever since. Sometimes it take a couple - use on a hot iron & wipe down the bottom of your iron. Always make sure you have a paper towel or some scrap fabric to iron on to remove the stuff. It kind of turns yellow/brown/black so make sure you get it off BEFORE really ironing anyting.