Dry Treat Acidic Cleaner is a heavy-duty cleaner for removing efflorescence, rust stains, timber tannings, grout haze and mortar stains from natural stone and porcelain. For use indoors and out, this patio cleaner has an advanced formula produces no toxic fumes and brief contact does not burn the skin. Dry Treat Acidic Cleaner should not be used on acid-sensitive stone like limestone. Before buying, we recommend that all customers read our Product Guide.