Calcium, Lime and Rust Stain Remover breaks up deposits quickly, removing stains and buildup. This professional-grade, concentrated acidic solution removes rust stains, limescale, hard water stains and calcium deposits. Use on stucco, cement, porcelain, glass, fiberglass and brick, making it ideal for use on toilets, sinks, tubs, shower heads and glassware. Mix with water and apply to surfaces with a brush, sponge or cloth. Then rinse with clean water.