Fatty Acids In Soap: Stearic Acid

Fats and oils are made up of fatty acids. Each possesses its own unique blend. Usually, our goal is to make a bar well-balanced for bathing, and it is the reason we mix oils rather than using just one oil. We take advantage of the properties of each oil to create that ideal bar. A bar that is hard and long-lasting, but lathers well and cleans without drying the skin is the goal of most soapmakers. Exceptions to this are not uncommon, but this is the standard.

The fatty acids we are concerned with for soap making are: lauric, myristic, palmitic, stearic, ricinoleic, oleic, linoleic and linolenic acids. Each brings certain properties to the process of soapmaking and the finished product. We will discuss one fatty acid per post.

Previous posts dealt with lauric, myristic and palmitic acids.

Let us talk about stearic acid. Stearic acid makes for a hard bar with stable, creamy lather. The oil highest in stearic acid is surprisingly, soy wax, boasting a whopping 87%! All butters are high in stearic, as well. Mango, cocoa, shea, kokum, sal, illipe, you name it, is high in stearic acid. Animal fats contain a respectable percentage, as well.

The hardness and creamy, stable lather from stearic acid make it a must for shaving soap. It is also preferred for hardening soaps high in fatty acids that would not create a hard bar by themselves. Soapmakers sometimes add it to high olive oil soaps, as well, to make the soap harden faster.

Stearic acid, in combination with lathering and conditioning oils, contributes to a great bar.

Join us next time to learn about the unique ricinoleic acid.

Until next time, may your days be filled with bubbles and wax.

Beth Byrne For Making Soap, Cosmetics & Candles Magazine