Understanding How The Fatty Acids In your Soap Oils and Butters Affect The Quality of Your Soap

by | Oct 15, 2021 | Uncategorized | 0 comments

The oils and butters we use in our soap making have different qualities – cleansing, lathering, hardening to mention a few. Knowing which qualities the oils have enables you to create the type of bar that you want and also helps you to substitute oils. The types of fatty acids in the oils and butters determine their quality in soap. One you understand which oils add lather, moisturise and harden your bars, you are able to start substituting oils to get the characteristics you want in your bar.

All the oils and cosmetic butters that are used in soap are made up of saturated and unsaturated fats. These fats have different qualities.

What is The Difference Between Saturated and Unsaturated Fatty Acids?

The 4 saturated fatty acids are lauric, myristic, palmitic and stearic. They will accelerate trace and will saponify more easily than unsaturated fats. Myristic and lauric acid fatty acids are more soluble in water, so they are excellent cleansers. These two fatty acids create soaps that produce a fast-forming, full and bubbly lather. Palmitic and stearic acids will create a hard, stable soap, with a creamy lather that lasts.

The 4 unsaturated fatty acids are oleic, linoleic, linolenic, and ricinoleic. Unsaturated fatty acids will be slower to trace and slower to saponify. They are less soluble and produce a milder and more creamy lather. Unsaturated fatty acids are softer in nature and decrease the hardness of the bar. Ricinoleic acid is different from the other three unsaturated fatty acids and increases the rate of trace and increases the rate of lather formation.

Lauric Acid

This is a saturated fatty acid that contributes hardness, cleansing, and big fluffy lather. Babassu, Palm Kernel, and Coconut Oil are all extremely high in lauric acid. However, too much lauric acid in a formula can feel drying unless properly balanced with a high superfat or high unsaturated fatty acid content.

Linoleic Acid

This is an unsaturated fatty acid that contributes to conditioning and moisturising and helps to create a silky lather. Luxury oils like Evening Primrose, Passion Fruit, Watermelon, Wheat Germ, and Hemp oils contain a lot of linoleic acid, but are usually too expensive to use in high amounts and have too short a shelf life.

Linolenic Acid

This is an unsaturated fatty acid that contributes to conditioning and moisturising and is typically very low in soap formulas. It’s found in high percentages in luxury oils such as Pomegranate Seed oil, but it’s also found in Flax, Kukui, and Hemp oils. There’s a small amount in Olive, Rice Bran, Canola, and Sunflower oils.

Myristic Acid

This is a saturated fatty acid that contributes to hardness, cleansing, and fluffy lather. A lot of exotic oils contain high amounts of myristic acid, such as Murumuru Butter, Tucuma Seed Butter, Monoi de Tahiti Oil, and Cohune Oil. However, Coconut and Babassu Oils contain a reasonable amount as well.

Oleic acid

Oleic is an unsaturated fatty acid that contributes to the conditioning and moisturising abilities of a soap. Oleic acid is what makes olive oil loved by soap makers. However there are oils that contain far more oleic acid than olive oil does, including high oleic Sunflower, Safflower, and Canola oils and the more expensive luxury oils like Hazelnut, Marula, Moringa, and Buriti oils.

Palmitic acid

This  is a saturated fatty acid that contributes hardness and stable creamy lather. It is found in large quantities in palm oil as well as tallow and animal fats. Cocoa butter is also a good source, containing 26%.

Ricinoleic Acid

This is an unsaturated fatty acid that contributes to conditioning and moisturising properties, and the stability of lather. It is believed to add a little slip and glide to the lather. Castor oil is the only readily available soap making oil known to contain ricinoleic acid, as it contains a huge 90%. Unfortunately there are no substitutes for this oil, as it has such a unique make up.

Stearic acid

This is a saturated fatty acid that contributes hardness and stable lather in soap making, similar to palmitic acid. It is found in Kokum, Illipe, Sal, Mango, and Shea butters. A commonly missed oil that contains a large amount of stearic acid is hydrogenated soybean oil.

Fatty Acid Properties In Soap

The table below gives you the properties of the different fatty acids and the oils and butters that have these fatty acids as their primary (largest) component and their secondary (second largest) component.

How To Use Fatty Acids To Substitute Oils in Your Recipe

If you use the chart below you can see how much of each type of fat is in each oil. This is an average amount as the composition of oils can change with weather and environment from year to year. This chart was made up from information from soapcalc.net, where you can find a larger range of oils and you can also suggest oil profiles to be added to the site. In this chart you can find substitutes for oils by looking at the composition of the oils and finding others with similar makeup.

I hope you will find this information useful. Remember to take notes when trying new recipes, so you can remember what was successful and what was not. There’s nothing more infuriating than finding the perfect recipe and then not being able to remember which one it was!

Author - Shona O'Connor

Author - Shona O'Connor

Soap Maker, Course Creator & Blogger

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