Mix solution in a plastic container using clean, warm water. Don't mix in metal container. Wear rubber gloves and eye protection. For removal of light mineral deposits and Portland cement grout haze or mortar residue on unglazed quarry or glazed tile with colored grout, mix 2 to 3 oz. (57 to 85 gm) with 1 gallon (3.78 L) of water. Mix 6 to 12 oz (170 to 340 gm) to 1 gallon (3.78 L) of water for unglazed tile or masonry that has gray-colored grout joints. For etching concrete or heavy-duty cleaning of old concrete, mix a minimum of 12 oz (340 gm) to 1 gallon (3.78 L) of water. Note: Do not use on marble or other polished stone. This product may etch some glazed tile. Test solution on a small, inconspicuous area before proceeding. Don't allow product to contact metal fixtures.