GCFR is a fast acting, heavy duty hydrochloric acid cleaner for textured, unpolished, natural and manufactured surfaces, including: Flamed & Honed Granite, Flamed & Honed Limestone, Tumbled & Honed Marble, Unglazed Ceramic Tile, Cleft & Honed Slate, Porcelain Tile, Quarry Tile, Sanded Grout. GCFR removes sanded grout & mortar residue, joint cement, lime & hard water deposits, efflorescence, rust and other heavy dirt and grime. Coverage: 500 - 2,500 square feet per gallon.