This product uses biodegradable organic acid salts to quickly remove hard water residue, rust stains and soap scum. For best results, remove water from toilet bowl or urinal. Pour 1 or 2 ounces of cleaner and allow to remain in contact with scale for 5 to 10 minutes. Brush or mop and thoroughly clean vitreous areas. Flush bowl and then rinse mop. Do not use on other than vitreous surfaces.