Soap scum, or lime soap, is attractive to mold and mildew and can become problematic if left untreated. One thing that can help get rid of it is good old-fashioned salt.
Salt is a natural abrasive, perfect for scrubbing away persistent residues without causing damage to the surface. Just don’t use it on any “soft” natural stone surfaces.
Baking soda has a base pH ideal for tackling sticky things like dirt and grease, while white vinegar is acidic and able to break down mineral compounds.
Combine one part baking soda and two parts vinegar in a bowl, resulting in a fizzing chemical reaction. Once that settles, add salt to the mixture to form a thick paste.
Using a sponge or brush, apply the paste to the affected areas. Gently rub it in, ensuring that the entire surface area covered in soap scum gets a good dose.
Wait half an hour to allow the ingredients to start the break-down process, then rinse off with water and dry. To prevent layers of scum from accumulating, use this paste weekly.