An oldie but goodie all about the oils used to make soap.
Soap is a bit like curry. Sure you can buy straight yellow curry powder but most chefs will tell you that the very best curry is made by carefully combining lots of different spices. The end result is a dish where all the spices work to create something greater than the sum of its parts. But…it pays to know your ingredients. Too much of something in your curry (usually chili) and you’ve got a flop.
Soap making (saponification) is a chemical reaction between a base and an acid. Generally, the base is sodium hydroxide while the acid is one or more oils or fats. Common soap making oils include olive oil, coconut oil, tallow, palm oil, shea butter, and cocoa butter. Each different kind of oil will bring different properties to the soap. Every oil will have a (usually) small portion of “unsaponifiables”, that is components that do not become soap. These can nourish the skin or provide other benefits.
Soap properties are usually described in terms of hardness, cleansing, conditioning, and lather (bubbly and/or creamy). When a soap maker develops a recipe they will carefully choose the ingredients and quantities based on what they hope to achieve in the finished bar. It’s a process that is usually tweaked and refined many many times and is why most soap makers don’t share their secret recipes!
Without getting too technical, the primary reason oils contribute different qualities is due to their chemical makeup, specifically their fatty acid profile. Here are some common soap making oils and their properties in soap:
Avocado—Makes a soft bar of soap that is rich in Vitamin E, B, D, and E. It makes a creamy and conditioning soap that is gentle and mild.
Apricot Kernel—This lightweight oil is conditioning and easily absorbed into the skin. It is also great for lotion.
Castor—makes a rich creamy lather. Too much can make a bar feel sticky.
Cocoa Butter—makes a hard bar with a stable creamy lather that is moisturizing.
Coconut—makes big fluffy bubbles, cleans really well, and creates a very white bar of soap. Too much can make a soap that is drying.
Lard (pork)—Similar to tallow. Makes a very hard white bar with a stable, creamy and moisturizing lather. Some makers choose not to use it for environmental and ethical reasons or because their customers prefer plant-based products.
Mango Butter—conditioning with a rich creamy lather.
Olive—considered by many to be the “king” of soap making oils. Olive oil contributes to a soap that is creamy and mild. It does not make big bubbles and can take a long time to cure (the drying time whereby the water evaporates) but will eventually make a very hard bar of amazing soap. 100% olive oil soap is called Castile soap.
Palm—makes a very hard bar which lathers well. Some people (including myself) choose not to use palm oil because of the documented environmental impact the plantations have on air quality (burning peat bogs for planting) and orangutan communities (devastating habitat loss). There is palm oil that is supposed to be sustainably sourced but enforcement is weak.
Rice Bran—Rich in Vitamin E and anti-oxidants. Makes a mild soap with small bubbles. Similar to (and often subbed for) olive oil.
Shea Butter—Shea butter is conditioning, moisturizing and gives a silky feel to soap.
Tallow (beef)—Makes a hard white bar with a stable, creamy and moisturizing lather. Some makers choose not to use it for environmental and ethical reasons or because their customers prefer plant-based products.
So, what do you do with all of this information???
Just like at the grocery store, read the labels of your soap! There are many other soap making oils; I have tried to list the most common ones here but you may also see canola oil, meadowfoam oil, safflower oil, and sunflower oil. Like a food label, the oils should be listed in descending order. Some soap makers will list ingredients using their Latin names, which is not required by law but hopefully, they’ll have the common name in parentheses. You may also see labels written as "sodium XYZ-ate" such as "sodium cocoate". This simply translates to "soap from coconut oil". Businesses will do this if they don't want to use the words lye or sodium hydroxide on their label. It's correct but a bit of a cop-out.
Most handcrafted soap is suitable for many skin types. Folks with sensitive skin might prefer a soap with a high percentage of olive oil or rice bran oil. People with oily skin might do better with slightly more coconut oil. If environmental impact is important to you, look for palm-free vegetarian bars.
http://www.lovinsoap.com/oils-chart/ http://www.naturesgardencandles.com/mas_assets/theme/ngc/pdf/soapoils.pdf http://www.soapqueen.com/bath-and-body-tutorials/tips-and-tricks/free-beginners-guide-to-soapmaking-common-soapmaking-oils/