Ferric oxide is a carrier that can also be found in bath products and makeup. A carrier does just what it sounds like - it helps carry a product to a surface by thinning or thickening the formula or simply ensuring even distribution of the other ingredients in the formula. We use ferric oxide because without a carrier, the product would not work with the same consistency across a surface. It can also be used as an abrasive, making a formula slightly gritty to help remove tough stains from surfaces. Ferric oxide will not harm most surfaces, but before using any abrasive product on a particular surface, you should test it on an inconspicuous place.