TileLab concentrated crystals mix with water to make a mild, safe to use, acid cleaner. Removes dried Portland cement grout haze and mortar residue from tile, concrete, and masonry. Safe for use on colored grouts. Removes hard water deposits, efflorescence, and also etches concrete. Use on all colors of grout, tile clay pavers, concrete and masonry. Do not use on marble or other polished stone. May etch some glazed tile. Coverage: Depending on the application, 1 lb. of concentrated crystals will make from 1 to over 12 gallon of Sulfamic acid solution. 1 gallon will clean approximately 300 sq. ft. area.