By Dan Koeppel
April 15, 2020
That bar of soap you’re so rigorously scrubbing your hands with multiple times a day is one of the most ancient consumer products you use, with one caveat: A lot of modern soap isn’t soap at all.
Soap likely originated as a by-product of a long-ago cookout: meat, roasting over a fire; globs of fat, dripping into ashes. The result was a chemical reaction that created a slippery substance that turned out to be great at lifting dirt off skin and allowing it to be washed away.
Fat reacts with lye—a substance made in ashes that can be pretty toxic, which is why soap makers need to wear protective gear—in a process called saponification. The word possibly comes from the proto-German saipo, which means “to strain”; the Latin sebum, which translates as “grease”; or from Mount Sapo, an Italian mountain whose location is now lost to history. (The story is that the drippings and ashes from the cook fires of the gods rolled down the hill and were discovered by filth-encrusted Romans.)
Modern soap makers—at least those working in small, artisanal operations—use the same techniques. The saponification process yields a thick slurry. As it solidifies, fat neutralizes the caustic lye. “After 48 hours, you’ve got soap,” says Natalie Wong, of Vancouver, British Columbia’s Pep Soap, which offers both vegetable- and animal-fat-based bars.
The slipperiness of soap lowers the surface tension of the water you’re mixing it with. Rubbing your hands together while washing allows dirt to temporarily bond with the water and soap and get washed away. The same process occurs with most viruses and bacteria that might be lingering on your hands. Soap doesn’t kill these bugs—it slips them up, lifting them from your skin, mixing them with water, and sending them down the drain. This chemical and mechanical reaction makes soap and water more effective, in general, than waterless sanitizing gels.
For most of the 19th century and into the early 20th century, soap companies made real soap. But in the early 1900s, German engineers discovered an alternate cleaning product: a synthetic called “detergent” (rough Latin translation: to wipe away). Detergents didn’t contain soap. Instead, they used enzymes that lifted stains off clothing and skin. American companies adopted and refined detergents, mixing ingredients to create surfactants, which, like soap, allowed dirt and grease to be pulled off the object being cleaned and into water.
The result is that what you’re calling soap today probably isn’t. At least not completely. “Most body cleansers, both liquid and solid, are actually synthetic detergent products,” states a Food & Drug Administration handout that provides the legal definition of soap.
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