The Chemistry of Soap

Have you ever noticed that if you walk down the soap aisle of your local store, the word soap doesn’t actually appear on any of the product labels? You’ll see things such as “bath bar,” “beauty bar,” “moisturizing bar” and “body wash,” but not the word soap.

The reason for this type of labeling is that these products aren’t actually soap and they cannot legally claim to be! So what exactly are they, you might wonder? They’re actually detergents. The manufacturers have removed some of the desirable by-products formed from traditional soap making and replaced them with artificial lathering agents, fragrances and synthetic chemicals.

But why would manufacturers do such a thing?  And what does this mean for your skin? To answer these questions, we first have to understand how soap is made and the chemistry involved.


(Our real soap! Honey oatmeal, lavender and peppermint soaps hand crafted in the apothecary.)

The Chemistry of Soap

Soap is made from a chemical reaction called saponification. In simple terms, a fat reacts with a base to form soap. But lets dig a little deeper and explain what happens on a more detailed level.

fats: Animal fats were traditionally used throughout history by soap makers, but vegetable oils can be used as the source of fat also. The molecules we are interested in are the building blocks of these fats and oils, called triglycerides

base: The base that is traditionally used in soap making is called sodium hydroxide. It’s commonly known as lye. The chemical formula for sodium hydroxide is NaOH and this is a very strong base!

reaction: One triglyceride molecule reacts with one base molecule to produce one molecule of glycerin and three fatty acid salts. These fatty acid salts are your soap molecules! Glycerin is a by-product that happens to be a humectant, meaning it draws water to your skin making it a great, natural moisturizing agent.


how soap cleans the skin:

Soap is able to clean our skin through it’s duel nature of being attractive to both water and oil. Each soap molecule contains one end that is attracted to water while the other end is attracted to oil/grease.  In this way, soap molecules are able to gang up on a molecule of grease and surround it, trapping it into a ball called a micelle. This little soapy ball of grease is easily rinsed away down the drain with water:



If we now go back to answer our questions about store-bought soap, we can see that glycerin is a desirable by product. Manufacturers will often remove the glycerin and replace it with synthetic ingredients because the glycerin is valuable and can be sold to be used in moisturizers and other beauty products.

If you are interested in keeping your bath and beauty products simple, safe and more natural, we highly recommend trying real, hand crafted soap. They produce a thick, luxurious lather and leave your skin soft, naturally. You can read more about our soaps here.





2 thoughts on “The Chemistry of Soap

  1. Hi – Take it from a chemist, the chemical reactions that you show are wrong. You are missing C=O on all of the long structures.


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