This may sound odd - but I had trouble with the build up on my iron and someone here suggested running the iron over a "used" dryer sheet. And since using them -there has been no build up. I used to use a Mr. Clean Magic Eraser and they worked well too, just used them before I used the iron because you cannot use them on a hot iron. I keep a couple of used dryer sheets pinned to the end of my ironing board and just run the iron over them a couple times if I am using starch. They last a very long time.