*MUNDANE MYSTERIES is sponsored by Airtron Heating & Air Conditioning.

We all know that washing our hands is important. But, much like towels, can bars of soap that we use to clean ourselves get dirty, too?

First, what is soap? Usually made of sodium or potassium salts from fatty acids & alkaline solutions, derived during a process called “saponification”, soap’s chemical makeup involves things called polar heads & non-polar tails. It’s a great emulsifier, which means it’s good at dispersing one liquid into another. So, when you wash your dirty hands with soap & water, those soap molecule tails are repelled by water but attracted to oils, which in turn attract dirt. Then, those tails cluster together & form “micelles”, which trap the dirt & oil. Those micelles are negatively charged & soluble in water, so they repel each other & remain in the water, where they’re easily washed away.

So, basically, soap gets your hands clean by latching onto grease, dirt, and oil more strongly than your skin does. Now, yes…you’re washing all those loose, dirt-trapping, dirty soap molecules away when you use soap…but does a bar of soap sitting on the bathroom counter or liquid soap in a bottle also get contaminated with microorganisms? The answer is “yes”, soap can, and indeed does, get dirty, though it isn’t really much of a problem. A few studies have been done where bars of soap, intentionally covered with E. coli & other bacteria, were given to test subjects who were told to wash up. None of those studies found any evidence of bacteria transfer from the soap to the subjects’ hands. Yay science!

Dirty soap can’t clean itself, however. So, how does a contaminated bar of soap get clean? The same way your hands do: a good, old-fashioned scrub-a-dub-dub. The friction from your hands rubbing against the soap, combined with the flushing action of the running water, removes any harmful microorganisms from both your hands and the soap & sends them down the drain.

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