Every time you iron your clothes, detergents, fabric softener, spray starch, bleach and other products used on them may stick to the plate. When the iron heats up, the brownish build-up can stain fabrics and the bottom of the iron may become sticky. When I was younger, I used to see my lola [grandmother] scrape the bottom of our flat iron with a knife. She did that to get rid of the build-up. It’s not a wise thing to do because it leaves scratches on the surface.
The right way to do it [got this from the article I’ve read] is to dampen a soft, clean cloth with warm water and dishwashing liquid. Don’t forget to unplug the iron, lol. Gently wipe the cooled plate. The water and dishwashing liquid will take care of the stubborn build-up. If you think your iron needs frequent cleaning, use bottled distilled water instead of tap water when you use the steam function.