The fatty acid profile of an oil or fat determines the way it behaves in a soap formula. Fatty acids are the individual components that make up the oil or fat. A fatty acid is comprised of a carboxylic acid group and a hydrocarbon chain. Saturated fatty acids are solid at room temperature; unsaturated fatty acids are fluid at room temperature. Studying the fatty acid components of soapmaking oils can help you determine which oils to use for the effect you want. These are the most important fatty acids in soapmaking:

• Lauric acid: softest of the saturateds; can be harsh; good lather

• Linoleic acid: goes rancid easily; use in small amounts in combination with more stable oils; contributes mildness; conditioning; polyunsaturated (likely to oxidize)

• Linolenic: double bonds; prone to rancidity; not that prevalent in soapmaking oils

• Myristic: softest of the saturated; can be harsh; hard bar; good lather

• Oleic: long shelf life; conditioning; main component of olive oil; monounsaturated

• Palmitic: saturated; long shelf life; hard bar; stable lather

• Palmitoleic: long shelf life

• Rinoleic: castor oil; has an alcohol component; conditioning; monounsaturated

• Stearic: saturated; hard bar; stable lather

Fatty acids are components of oils. Here are the primary fatty acids in some common soapmaking oils:

• Almond oil: mostly oleic

• Apricot oil: .25 linoleic, mostly oleic

• Avocado oil: mostly oleic

• Castor oil: mostly linoleic

• Cocoa butter: .33 oleic, .3 palmitic, .33 stearic

• Coconut oil: mostly lauric

• Emu oil: .45 to .50 oleic, .22 to .25 palmitic, .08 to .10 stearic, .06 to .10 linoleic

• Grapeseed oil: linoleic

• Hemp seed oil: mostly linoleic

• Kokum butter: .03 palmitic, .67 stearic, .28 oleic

• Kukui nut oil: .48 linoleic

• Lard: .22 palmitic, .15 stearic, .41 oleic, .12 linoleic

• Macadamia nut oil: mostly oleic

• Mango butter: .33 to .5 linoleic, .25 to .5 stearic

• Olive oil: mostly oleic

• Palm oil: over .3 oleic, about .5 palmitic

• Palm kernel oil: about .5 lauric

• Sal Butter: .04 palmitic, .47 stearic, .44 oleic

• Shea butter: .5 oleic, .3 to .5 stearic

• Soybean oil: mostly linoleic

• Tallow: .9 lauric, .03 myristic, .25 palmitic, .19 stearic, .36 oleic

Some oils are excellent superfatters, such as:

• Castor oil: Used for shampoos, transparent soaps, and for superfatting cold- and hot-process opaque soap; the best superfatting agent for boosting lather.

• Kokum butter: Great for superfatting, similar to shea butter.

• Mango butter: Use in small amounts for superfatting.

• Sal butter: Doesn't get rancid, adds emollient quality.

• Shea butter: Makes a very luxe, hard bar; also great for superfatting.