The Bio-Clean Hard Water Stain Remover removes severe hard water stains that have been there for up to 30 years with well water/ very hard water. The Hard Water Stain Remover removes all calcium and mineral deposits, rust, tree sap, paint overspray, mildew, mold, hair dye & food coloring stains. The multi-surface Hard Water Stain remover works great on shower doors, tile, chrome, porcelain, fiberglass, stainless steel, aluminum, brass- all glass, metal and stone surfaces, completely restoring the surface back to its original condition.