There is a lot of uncertainty regarding how lye interacts with beneficial compounds in certain soapmaking ingredients. Will the luscious properties of fresh aloe gel or herbal infused tea survive the “lye monster?” However, it is well understood how fatty acids undergo saponification. This is why creating soap recipes is largely a mathematical formulation reduced down to fatty acid composition.
So let’s go over the common fatty acids found in soapmaking (keeping it simple).
Lauric acid and myristic acid are two saturated fatty acids that are the primary components of coconut oil, palm kernel oil, babassu oil and murumuru butter. They contribute to a very hard, cleansing, long lasting bar of soap with a big, bubbly lather. Sounds ideal, but… in too high a proportion the soap will be harsh, incredibly drying and irritating for sensitive skin.
Next up are palmitic acid and stearic acid. These are also saturated fatty acids that promote hardness, stability, and a creamy, mildly conditioning lather. Soapmaking oils high in these fatty acids are tallow, lard, shea butter, cocoa butter and palm oil. Stability in part refers to the level of water solubility in the final product of the soap. A less soluble bar can withstand wetness without melting away. A drawback of, say, a very high shea butter soap is that it will not have a big, bubbly lather nor the power to clean dirty things very well.
Ricinoleic acid is a bit of a unicorn fatty acid only found in castor oil. It has the unique ability to provide exceptionally conditioning qualities to soap while also boosting the lather and bubbles. Usually castor oil is kept to around 3-7% of a final bar, because in larger quantities many have experienced an unpleasant stickiness to the bar and a tendency to leave a residue.
Moving on to unsaturated fatty acids. Oleic acid, the MVP conditioning element of soap. Since it is a monounsaturated fatty acid, it has a longer shelf life and more stability than polyunsaturated fatty acids. The traditional source is, of course, olive oil. Olive oil is a unique liquid oil in the sense that it also contains small amounts of saturated fatty acids – thus it produces some level of hardness in soap when given long enough to cure. Oleic acid is also relatively high in tallow, lard, shea butter, cocoa butter. And canola oil, which I will get to soon! The drawback to soaps high in oleic acid, while extremely mild and moisturizing, is that they are not hard or long lasting, there is almost no lather, and the lather itself is slimy and ropy. Some perceive a residue on the skin or hair.
Linoleic acid and alpha-linolenic acid are the primary polyunsaturated fatty acids. They offer no hardness, bubbles, stability or cleansing properties but they produce a moisturizing, luxurious silky lather that feels light as a feather. Any of your luxury seed oils are high in these fatty acids, like rosehip oil, hempseed oil, argan oil, grapeseed oil and safflower oil, to name a few. Because of the double carbon bonds, these oils are delicate and prone to rancidity. (Read more in my PUFA article). Most soapmakers keep these oils to a minimum, use them as the superfat, and/or take precautionary measures like buying the oil as fresh and unrefined as possible, adding rosemary co2 extract to the bottle once opened, and storing in the refrigerator.
Two interesting oils that don’t fit neatly in these categories are jojoba oil and avocado oil. Jojoba oil is composed mainly of gadoleic acid. In soapmaking, it is used in small amounts to increase the shelf-stability and conditioning aspects of the bar. It contains a vast proportion of “unsaponafiables”: beneficial compounds that survive the lye monster unaltered. Avocado oil contains high amounts of oleic, palmitic and linoleic acid. It is a step between the palmitic/stearic ingredients and the oleic/linoleic ones. It offers a bit of hardness to the bar, and a moderate conditioning factor.
Let’s finally get to the elephant in the room. Canola oil!? Really?
Canola oil is found in almost every one of my soap recipes. It is similar to olive oil, but with slightly less oleic acid and more linoleic acid. Because I make soap with organic and/or wildcrafted ingredients, I have to be strategic with my choices lest I wind up with a $20 price point for a bar of soap. Due to the high prevalence of fake/adulterated olive oil on the market, I only trust a few sources. After many tests comparing soaps made with olive oil vs canola oil, I was surprised to admit (and especially with hair bars), that the canola oil soaps performed better. And I do have to say, this felt like a win-win. There was a part of me that simply did not align with using such an expensive and profoundly healthy ingredient for internal consumption in my soaps. So I have stuck with my organic, expeller pressed USA-grown canola oil.
Tallow tangent: After a few years of making soap, drawing up hundreds of theoretical recipes on soapcalc.com, and becoming utterly fixated on creating the perfect hair bar, I was struck by something I somehow hadn’t considered: 100% tallow soap. Tallow is an important staple in my recipes, but I guess I figured it wouldn’t be quite conditioning enough. In my rabbit holes of research I had encountered a veteran soapmaker mentioning just how conditioning palmitic acid can be, and that soapcalc.com doesn’t quite account for this in its calculator.
Dang, wouldn’t that be something if all this time the perfect soap was just a simple one ingredient soap! Not just any one ingredient, but one that is easy to source locally as well as easy to infuse with herbs. Tallow has a beautiful fatty acid composition. Just a wee bit of lauric and myristic acid account for some bubbles and cleansing factor.
The process of making the soap was easy, straightforward, no hangups. Double infused the tallow with chickweed and plantain ahead of time. Stirred in some ground oats for a bit of exfoliation. Hot processed it so I could add some raw goat milk in at the end but keep a light color. The final product was very hard, very stable, and very conditioning. But it took some effort to work up a lather and I realized it simply could not cut through grease, remove tomato resins from my gardener’s hands, or clean my baby’s poopy bum to the point where there was no poop smell lingering at the end.
Thus, I would recommend 100% tallow soap as an extremely mild body or face soap for those who don’t get too dirty 😉
More soap sagas to come!
