When hard water mixes with soap (and other residues like dirt, body oil, and bath products), it can result in a gray or white film that is known as soap scum. It's usually found on shower doors, ...

No matter the material or price tag, no bathtub is immune to dirt, especially soap scum. "In short, soap scum is the hardened fats from soap bars ... binding to the calcium and magnesium in the water, ...

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