The Origins of Soap: What is Soap?


Wash your hands, young man (lady)!

It is everywhere –from bathroom signs to that age-old parental declaration—you should wash your hands. But, exactly what is soap, and how does soap, a product made from fat and ash, actually clean?

It’s in the science. Yep, I mean the science of cleaning.

As mentioned in the first article in the series, soap is made of oils and fats. These fats and oils can come from plant sources, like olive oil, and animal sources like beef fat (tallow.) Oils and fats are made of triglycerides, which are made of fatty acids (No, I’m not calling anyone a bad name!)  These fatty acids make up long chains made of a carboxylic acid group and a hydrocarbon.

pH scale showing common substances

Image via Wikipedia

Ball-and-stick model of the α-Linolenic acid m...

A fatty acid chain

When fat and an alkali, like lye (remember the whole Ph scale) come together, it creates a chemical reaction. Lye was once made from wood ash; however, today it is manufactured commercially.

 Lye is necessary to process certain
foods, like pretzels and olives.

This creates a molecule that has two ends. One end consists of hydrocarbons and the other end consists of the weak acids from the fat or oil and the alkali.

The hydrocarbons end of the molecule hates water.  It is hydrophobic. (water + fear)

However, it loves oil.

The other end of the molecule loves water. It is hydrophilic
(water + love)

When soap encounters oil and dirt, it attracts the hydrocarbon molecule. The water attracts the hydrophilic molecule. This push and pull allows the dirt to loosen and with a little manual manipulation, you and anything else you soak in it is
clean.

This is the chemical process of soap making called saponification. However, actually making soap is a little less clinical. (Although, when you
make soap you feel like a mad scientist.) The next post will be about why a person would want to.

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4 thoughts on “The Origins of Soap: What is Soap?

  1. Its like you read my mind! You seem to know a lot about this, like you wrote the book in it or something. I think that you could do with some pics to drive the message home a little bit, but other than that, this is magnificent blog. An excellent read. I’ll certainly be back.

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