Soap and hand washing go together like sunscreen and a day at the beach. Psychologists suspect that washing hands with soap is a major formative block of a civilized person’s ego. My earliest childhood memory is of my mom standing in the doorway of our bathroom, arms akimbo, her head at a slight angle, looking at me as I turn around to make my way out the bathroom after washing hands. I halt as she quizzes: “Did you wash your hands with soap?” “Yeeees?” – I reply. “Let me smell them.” A rhetorical demand, obviously…
Of course, nobody ever bothered to explain why hands had to be washed with soap. I mean, it is supposed to kill germs, but so does clean water. What does soap actually do? Let us have a look.
You should be pleased to find out that soap is a well-established time tested product. Ancient records of soap recipes can be traced back to centuries prior to the beginning of the Common Era. However, we should be careful when drawing conclusions form this. All this ancient soap may not have been, and probably initially was not, used for washing human body surfaces.
It turns out the main function of soap is degreasing. Soap is a chemical; its molecular structure is such that it is able to bind water to oil – an impossible feat if attempted unaided. It is literally a connector piece, one end of which latches onto a water molecule, and the other grabs onto a molecule of fat. The more soap is used, the more grease is suspended in water. The mechanism is simple and can be applied to washing clothes, dishes and, of course, skin… and hair.
Still, despite its simplicity, even pure soap can differ in its composition at the molecular level. Every soap molecule carries a fatty acid that the soap making process breaks off from oils used as the initial raw ingredients for the soap. These fatty acids differ in length. Yes, actual physical length due the different number of hydrocarbon (CH2) atoms joined together in a chain. These fatty acids also differ in shape (some are straight – these are called saturated fatty acids, some are curved – unsaturated). Depending on what ingredients are used, any given soap bar will be composed of a bouquet of fatty acids. Shorter saturated acids yield harder, better cleaning soaps. Longer unsaturated acids produce gentler, less drying soap. The former is great as a general purpose cleaner, the latter is better for personal hygiene applications.
It should come as no surprise that the longer chain unsaturated fatty acids are often found in expensive plant derived ingredients. Some exotics that produce luxuriously rich and gentle soap are walnut oil, wheat germ oil, peach kernel oil… You get the idea. On the other hand of the spectrum are commercial industry staples like abundant (but often non-sustainable) palm oil and more expensive (but environmentally friendlier) coconut oil.
Another product of natural soap making process is glycerin. Glycerin attracts moisture and is a cosmetic ingredient with proven skin softening qualities. Glycerin (in its purified form) can be found in food, where it acts as a preservative and a humectant. Most large scale soap manufacturers remove glycerin from finished soap – it messes with their molding process and shortens soap shelf life. Artisanal soap producers usually leave glycerin be, which makes their soap gentler and less drying.
Oh, almost forgot. Some products that masquerade as soap aren’t actually soap. They can be called hand wash, hand cleaner and other silly names. The active ingredients in these products are man made crude oil derivatives. They are bad for the environment and can be carcinogenic. It is a good idea to read the label on those.
Phew… This about covers the basics of soap, what it is and what it does. Next, let us ponder whether soap and shampoo are at all necessary. The answer is less obvious than you might think…