After putting tap water in your iron repeatedly to make steam, you may begin to notice a buildup of lime scale. While lime scale is natural, you should descale a steam iron as soon as possible after you notice it to keep the steam channels inside the iron from becoming clogged. There are products on the market which help descale your iron, but you can do it at home cheaply with a vinegar and water solution in very little time.
Empty out your iron into a roasting pan or large pot if there is any water remaining in it. Turn the iron on and set it to the "cotton" setting.
Mix together in a measuring cup one part vinegar and two parts distilled water. Pour the vinegar and water mixture into the iron.
Turn the iron off and hold it with the heat plate facing downward over the roasting pan or pot. Allow the vinegar and water mixture to drain out of the iron into the pan.
Refill the iron with distilled water to rinse the vinegar from the inside of the iron. Let the distilled water drain out into the pan as well. The iron should be ready to refill and use as needed.