Fatty Acids In Soap And What They Mean

Fats and oils are made up of fatty acids. Each oil possesses its own blend, the fatty acid profile. Usually, we seek to make a bar with qualities that are well-balanced for everyday bathing, and mix several oils to take advantage of the dominant properties of each oil. We want a bar that is hard and long-lasting, but one that lathers well and cleans without drying.

Certainly, not every bar matches this set of characteristics. Many are developed for special purposes and situations; but for the most part, this is the ideal.

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

Myristic Acid

Last time, we discussed lauric acid, the medium chain fatty acid that gives us hard, lathering soap. This time, we will discuss myristic acid. If you missed it, here you go.

Myristic acid is somewhat unique in that no oils are actually high in myristic other than nutmeg butter, which comes in at 83% myristic acid. Instead, the oils high in lauric acid also possess myristic acid in lesser percentages, ranging from the teens to 26% that mirror lauric acid’s properties.

Look for the common high-lauric oils– coconut, babassu and palm kernel, as well as the less known, less available, murumuru, tucuma and cohune butter. They are high enough in lauric acid, but are accompanied by myristic acid. As a result, oils with significant percentages of myristic acid and lauric acids create the same kind of bar that lauric acid does—hard, cleansing and bubbly, but a cleansing value that could be considered harsh, as well as a bar that “melts” in the bath or shower more quickly than we typically like.

The common usage rate of 20 – 30% assures the qualities of lauric/myristic, but in a low enough percentage that most users are not bothered by the cleansing value. Other oils are added, of course, to make the bar last longer and to provide other important characteristics.

Of course, no usage rate rule is actually a rule. Exceptions abound for a number of reasons, so consider them as guidelines only. Let experience and purpose guide the actual formula.

Stay tuned! The next blog post is all about palmitic acid.

May your days be filled with bubbles and wax.

Beth Byrne, for Making Soap, Cosmetics & Candles

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