Soap scum, also known as lime soap, is a white, chalky residue that appears as a white or gray filmy layer that covers the surfaces around our showers, bathtubs, and sinks. It is made by calcium stearate and magnesium stearate, among other materials, mixing with hard water. Hard water contains calcium and magnesium ions, which react with the surfactant anion to give these metallic or lime soaps. Soap scum can be found on shower curtains, bathroom fixtures, bathtubs, shower doors, tiling, and more. It is formed into a solid substance when soap is being used in hard water. Homes with mineral-filled hard water are much more likely to have soap scum buildup, which can be difficult to remove if left for too long, as soap scum continues to build up each time the area around it is used. Soap scum also includes body oils, dead skin, hair, and whatever dirt may be floating around your tub.