When I made my first batch of shaving soap, I didn’t do it because I wanted to sell it. I didn’t even do it because I wanted to shave with it. I did it because I wanted to understand the ingredients in shaving soap. This is perhaps one of the best skills to have in this hobby; even if it’s just peripheral knowledge you lean on. You’re not going to leave this article knowing every ingredient in the cosmetic dictionary, but hopefully you’ll leave this article understanding the basics of shaving soap chemistry and what categories of things you should look for on a label.
First, a brief explanation of what soap is. A soap is a “salt of a fatty acid”. In other words, when triglycerides – like the ones found in fats and oils – are mixed with a strong base, they undergo a transformation in what is called saponification. In so many words, saponification is what turns stuff like rendered fat (tallow) into something that cleans your skin!
For the purposes of this explanation, I’m going to separate ingredients you’ll see into 3 groups: oils/fats/butters, the lye solution, and additives.
- Oils/fats/butters (for the sake of brevity, I will refer to them as simply “oils” from now on) – these ingredients are the backbone of any soap. Which oils are used and in what quantities is what plays a large (perhaps the largest) part in performance of a soap. Each ingredient in this category contains a different makeup of fatty acids, and each fatty acid has a unique contribution to the properties of any soap. Think of it like a mixed drink. The non-alcoholic ingredient in an alcoholic beverage plays perhaps the most critical role in determining what the drink is. Like tomato juice in a bloody mary. Swap it with cranberry juice and it’s no longer a bloody mary.
- Lye solution – sodium hydroxide (NaOH) and potassium hydroxide (KOH) are the two strong bases usually found in ingredients lists. When they are dissolved in liquid, they can hydrolyze / react with fatty acids. KOH and NaOH are most commonly dissolved into distilled water, but can also be dissolved into various milks, plant-based liquids (e.g. aloe vera juice), or other stuff like beer. Going back to our mixed drink analogy, think of KOH and NaOH as the alcohol in the drink. You need it to make the drink alcoholic (duh), just like you need a strong base to make oils into soap. Some people are thrown off by seeing “the hydroxides” on a soap label, but they are 100% necessary. Again, can an alcoholic drink exist without alcohol? A soap made correctly will contain no NaOH or KOH once it’s made, though. It’s “used up” in saponification.
- Additives – this category includes additional ingredients that give the soap different characteristics. Extracts can have skin benefitting properties, chelating agents can fight the effects of hard water, fragrance adds scent, and so on. Additives are not necessary to make a soap “work”, but most all soap contains some additives. The additives in our metaphorical mixed drink would be things like garnishes and spices. The drink would be fine without them, but is enhanced because of them. The same is true in soap.
So let’s put this into practice shall we? And to do that, I’m going to use a fan favorite as our hands-on example: Cella.
The ingredients in Cella are:
Coconut Oil, Tallow, Stearic Acid, Water, Potassium Hydroxide, Sodium Hydroxide, Potassium Carbonate, Sweet Almond Oil, Tetrasodium EDTA, Fragrance
Let’s split these up into our three categories:
- Oils – Coconut oil, tallow, stearic acid, sweet almond oil
- Lye solution – Potassium hydroxide, sodium hydroxide, water, and potassium carbonate* (see my note below regarding potassium carbonate – it’s a curious addition!)
- Additives – Tetrasodium EDTA, fragrance
Though there is no standard definition of a soap “base”, I think of it as the combination of oils. So in this case, coconut oil, tallow, stearic acid, and sweet almond oil make up the Cella base. We don’t know the precise amounts of each used, but we know the order of prominence (because it’s always listed that way on the label).
One item I would point out is that the combination of coconut oil, stearic acid, and tallow is a very common and traditional shaving soap formula. All three of those are used in The Original Collection, in fact! Stearic acid is the cornerstone of any high-lather shaving soap and you should always look for it to be high on the ingredients list. Tallow is great for mild, high-lather properties and coconut oil forms a very stable lather (but can be a bit drying). In contrast to low-lather oils like olive oil, this base makes for a great shaving soap!
The lye solution is made of KOH, NaOH, and potassium carbonate. In most good-quality shaving soaps, you should look for KOH. It’s what helps to give the soap a softer feeling. NaOH makes a hard bar of soap. I’m not saying there aren’t great quality hard pucks out there, but bath soap makers are known for making mediocre shaving soaps by simply altering a bath soap recipe; and bath soap is made with exclusively NaOH. So it’s just something to look out for.
*The presence of potassium carbonate is an interesting one in this soap. Potassium carbonate is another strong base traditionally used in soap making, but not often seen anymore, and certainly not in artisan soap (that I know of). In practice, it is “weaker” than KOH or NaOH and not as effective in breaking down triglycerides into fatty acids. My best guess in how this is used is that it’s added as a “safer” reagent to make sure the pH is kept at reasonably lower levels than if the hydroxides alone were used. Theoretically, this may also reduce (or eliminate) the need for a superfat and/or reduce the cure time necessary. But who really knows! There’s always mystery in reading ingredients. It’s part of the fun!
Now let’s look at the additives. You can probably guess what fragrance is used for. Tetrasodium EDTA is one of the most popular chelating agents around. Hard water can interfere with the effectiveness of soap. If you’ve noticed a single soap of yours perform differently in different parts of the world, the water is probably the reason. A chelating agent counteracts this effect. You probably won’t see EDTA in many artisan shaving soaps, however. It’s been shrouded in a little controversy in years past about its toxicity. That being said, you shouldn’t feel the need to avoid it unless you have personal convictions for doing so. It’s perfectly safe for use and always used in very small overall quantities.
This brings up a good point about cosmetic ingredients in general. Just because it’s hard to pronounce doesn’t mean it’s bad for you. Yes, there are plenty of ingredients that shouldn’t be in soap. But some of the most common skin irritants aren’t preservatives or chelators. They are essential oils! If you’re worried about an ingredient in a shaving soap, just email the artisan and ask what that item is used for and why it was chosen.
Case in point, you might be thinking, Garrett, I just looked at my favorite shaving soap label and it looks like ALL that’s in there is chemicals! What’s going on?! What is this potassium tallowate and cocate and all these -ates?! When you see an ingredient end in -ate, think of this as the saponified version of an oil. Coconut oil is an ingredient, but when a strong base, like potassium hydroxide, breaks up a triglyceride and forms a soap, it’s no longer coconut oil. It’s something else. It’s called potassium cocoate. The reason we end each word with -ate has to do with a chemical naming convention when an organic acid loses a proton, but in layman’s terms: coconut oil + potassium hydroxide = potassium cocoate. This same nomenclature is used in all other cases as well. Tallowate (tallow), safflowerate (safflower oil), and so on.
Let’s recap a bit.
- There will be three main categories of items on a shaving soap label; the oils, the lye solution, and additives.
- High-performing shaving soaps typically have stearic acid high on the ingredient list. So be on the lookout for it.
- Though not always the case, the presence of potassium hydroxide is usually encouraging, as it indicates the soap was created by someone who understands the specific needs of a shaving soap.
- When ingredients end in -ate, it’s just a different way to list the same ingredients. Another way to think of this is listing what comes “out of the pot” instead of what goes “into the pot”.
Similarly, here’s a short list of items that you generally want to be wary of on a shaving soap ingredient list:
- The presence of olive oil. The shaving soaps that I’ve seen that contain olive oil are typically bath soap “bases” with a few extra ingredients sold under the illusion of shaving soap. In normal soaping use, olive oil does not have beneficial properties for a shaving soap.
- A well-made soap does not need preservatives because the pH is naturally high enough that it does not allow for bacterial growth.
- Propylene glycol. I don’t know much about this ingredient except that it is a natural gas bi-product. The reason I put it on this list is because it’s been in every shaving soap I suspect of being a melt-and-pour base. By “melt-and-pour”, I mean a pre-made soap that you literally melt down, add some fragrance to, and pour into a mold. I think propylene glycol must have something to do with allowing a M&P soap to be heated and re-heated easily, but I don’t know for sure. But I’ve found it to be a pretty good way of identifying a M&P. For the record, there’s nothing inherently wrong with melt and pour soap, I just have yet to use one that can stand up to a shaving soap that has been created from scratch.
I’ll leave you with this: I hope this is modestly helpful to you, but none of it is gospel. There are exceptions to every rule. I’m sure someone could make a great shaving soap tomorrow that contains some olive oil, for example. Cosmetic chemistry is a vast, deep, and expansive area of study. I don’t claim to be any expert, but I find it incredibly interesting and what I’ve outlined above has just been my own experience in making soap, trying other people’s soap, and relentlessly reading ingredient labels.
Start reading some of those labels, and maybe I’ll make a convert out of you, too! Until next time.