As a general rule, the gel is safe to use on any non-absorbent hard surface, but ALWAYS do a spot test before doing a full application. A spot test involves placing a small amount of gel in an inconspicuous area for up to 24 hours to be 100% certain that no damage will occur to the area you are trying to treat. We have tested it on painted walls, tiles, metal shower frames and manufactured stone bench tops with no issues.