How Does Soap Scum Form?

Jeff Wysaski

Soap scum is public enemy number one when it comes to keeping a bathroom clean. This chalky, scaly layer of white or gray film accumulates over time and can be found anywhere that soap meets water on a regular basis.


Whether it's mucking up your bathtub, shower, faucets or kitchen tile, knowing the facts about soap scum can help you combat the problem.

What Is Soap Scum?

Many people assume that soap scum is simply soap residue that has accumulated on a particular surface. The truth is that soap scum is actually a mixture of soap and minerals found in water. These minerals give soap scum its scaliness and make it difficult to scrub away.

Common minerals that contribute to soap scum include calcium, magnesium and sulfates. Water with high levels of these minerals (known as hard water) produce greater amounts of soap scum. Many people who encounter hard water in their homes install a water softener.

Do You Have Hard Water?

Discovering whether or not your home plays host to hard water is an easy endeavor. Simply put, if you have a hard time working soap and water into a lather, you probably have hard water. The frequent applications of sponge and bathroom cleaner to your bathtub are another indication.

Minimizing Soap Scum

Beyond installing a water softener, there are other ways to curtail soap scum. Some tips include:

Use liquid soap: bar soap contains talc, which facilitates the formation of soap scum. Add dish soap to baths: a small amount of liquid dish soap in a bathtub helps hinder the formation of soap scum. Clean regularly: a weekly tub scrubbing may not reduce the frequency of accumulation, but makes removal easier.

Removing Soap Scum

An ammonia-based solution is often the best way to remove soap scum. Most commercial bathroom cleaners that boast soap scum removal also work. To get rid of the soap scum, simply spray the cleaner onto the affected area, let is sit for a few minutes and then use a sponge or stiff bristle to wipe out the soap scum. Be sure to rinse the area well to ensure the soap scum is washed down the drain.