Fats and oils come from many different plants or animals around the world, and each one adds unique properties to soap. Properties are determined by which fatty acids are in an oil. There are many fatty acids, but these are the most common and important to soapmakers.
These fatty acids and their properties include:
- Lauric Acid: Provides hardness, cleansing, and bubbly lather
- Linoleic Acid: Provides conditioning
- Myristic Acid: Provides hardness, cleansing, and bubbly lather
- Oleic Acid: Provides conditioning
- Palmitic Acid: Provides hardness and a creamy lather
- Ricinoleic Acid: Provides conditioning, bubbly lather, and a creamy lather
- Stearic Acid: Provides hardness and a creamy lather
Oils can be readily available in grocery stores, such as canola, coconut, palm, or olive oil. Other oils are exotic, at least to certain areas of the world, and can be expensive, such as shea and mango butters and emu oil. Almost any vegetable/fruit oil can be used in soap.
Even after you have selected your oils, you cannot simply pour them into a bowl and mix them with lye. This is because each oil has a saponification value, or SAP, which is the amount of lye required to turn 1 gram of the oil or fat into soap. The SAP values have to do with the fatty acids of each oil. All of the vegetable and animal oils have them, but they are a little different in each plant or animal type.
The American Oil Chemists Society (AOCS) publishes the standardized SAP value range for most oils. There is a range because there may be slight differences from one crop to the next. You will learn more about selecting oils and using SAP values in the recipe lecture.