The shaving and skin care enthusiasts over at Wicked Edge have inspired me to write a little about our favourite foamy stuff…soap!
Let me start off by explaining how soaps work…
Soaps belong to a family of chemicals called surfactants. Soap, detergent and foaming agents are all surfactants. Most cleansers contain surfactants – don’t let the marketing fool you! “Detergent-free” or “soap-free” doesn’t make it “good” for your skin, nor does it really mean anything. Cleansers that don’t contain surfactants clean by physical rubbing or absorption, like clay powder or pumice.
Surfactants work by being attracted to both oil and water. One end of the surfactant molecule is attracted to oil, and the opposite end is attracted to water. When you lather it on your skin, the surfactant molecules join together to form bubbles. The ends of the molecules that are attracted to oil are on the inside of the bubble, and the ends of the molecules that are attracted to water are on the outside of the bubble. This traps oil (along with dirt and bacteria) from the surface of your skin inside the bubbles, and since the ends that are attracted to water are on the outside, they’re easily rinsed away.
Now on to saponified oil soaps…
Saponified oil soap needs two components, a fat and a caustic. The fat can be anything from beef fat to grape seed oil and the caustic are either sodium hydroxide or potassium hydroxide.
The reaction of the fat (specifically the triglycerides in the fat) and the highly alkaline caustic causes a chemical reaction which creates soap.
When sodium hydroxide is used, the soap becomes a hard block. Potassium hydroxide creates a gel-like soap, which is diluted with water to make liquid soap.
Different types of fat produce different properties in the resulting soap. Fats are made up of fatty acids which fall in to 3 categories: saturated, mono-unsaturated and poly-unsaturated.
Saturated fatty acids produce foamy, but generally more drying soaps. Mono-unsaturated fatty acid produce soaps with moderate foam, and are more moisturizing. Poly-unsaturated fatty acid soaps are highly moisturizing, but barely foam.
This is why most saponified oil soaps are mainly composed of either coconut or tallow (beef fat). Their saturated fatty acid content means their soap lather a lot. Soap made with grapeseed oil (which is 70% poly-unsaturated) will result in a soap that is not very foamy, but more moisturizing than a coconut oil soap.
As an aside, castor oil has its own special fatty acid, ricinoleic acid. This fatty acid creates a sticky, paste-like foam. It’s usually added to other oils to change the density and structure of the bubbles in the resulting soap.
An important by-product of the chemical reaction between the fat and the caustic is glycerin. Glycerin or glycerol is a humectant, meaning it can bind moisture from the air in to the skin. It’s a very commonly used moisturizing ingredient and is generally separated from the soap and sold in moisturizers where it can fetch a higher price!
There are also substances in fats that are unsaponifiable, this means that the caustic doesn’t convert these substances in to soap. Unsaponifiables can provide moisturizing or antioxidant benefits to the soap. For example an unsaponifiable component of olive oil, squalene is a great non-irritating moisturizer.
Saponified oil soaps are about as close to natural or organic as you can get, as long as the fats and oils that were made to use the soap are natural or organic, of course.
The easiest way to check if your soap is a saponified oil soap, is to look at the ingredient list.
The way that a saponified oil or fat is listed in the ingredients list is like so, “Sodium ____ate” where the blank is the root of the name of the oil.
For example, Sodium Tallowate is tallow (beef or sheep) fat saponified oil soap. Sodium Olivate is olive oil saponified oil soap. Sodium Palmitate is palm oil saponified oil soap. Sodium Cocoate is coconut oil…hopefully you get the idea!
Generally the name is just Sodium ___ate, if it’s 3 words like Sodium Lauryl Sulfate, it’s not a saponified oil soap. There are some exceptions, but they’re easy to recognize like Sodium Peach Kernelate (Peach kernel oil soap).
Are there benefits to using a saponified oil soap? Beyond the “naturalness” of the soap, saponified oil soaps are pretty similar to other cleansers. It does come with a built-in moisturizer, glycerin, but those can be added in to other types of cleansers as well.
A down side is that due to the caustic, saponified oil soaps tend to have higher pHs than other types of cleanser. This can cause stinging if your skin is irritated or sensitive. People who make saponified oil soap can add acids like citric acid to lower the pH of the soap, but this can also reduce the foaminess of the soap.
Another benefit of saponified oil soap is that they’re easily melted, boiled, sanitized and reformed in to new bars. There’s actually an organization called Clean the World that processes used soaps and sends them to developing nations and disaster areas to help save lives! Pretty cool!