Are pH balanced soaps better for your skin? Learn to test the pH of your soap and how to neutralize liquid soaps if you need to.
Checking the pH of your liquid soap: The Why…
Unlike bar soap recipes that tend to use excess oils to chemically react with all of the lye, leaving you extra conditioning oils for your skin, liquid soaps are usually calculated to use either the exact amount of oil for the lye, or even use a “lye excess” instead.
Why would you not add extra oils to liquid soap?
Liquid soap recipes are calculated without excess oils to keep the final soaps clear. Having too many oils in a liquid soap will turn the soap cloudy at first, and can even lead to separation if there are enough of them.
Some people like making “liquid soaps” by dissolving bar soap in water, but every time I've tried it, I've just ended up with a gloppy mess that looks gross in a glass soap dispenser. The soap mixture always separates into two layers, one being opaque and cloudy, and it just doesn't look very nice.
I personally think that if you want a liquid soap, you should just go ahead and make real liquid soap instead because you'll have a much nicer final product. It can be intimidating, but once you get over the fear factor, I think you'll find that it is a rewarding hobby. If you're interested, I have a recipe up for a liquid castile soap using only olive oil, and a liquid coconut oil soap.
I decided to risk a bit of cloudiness in my recipes, and worked them to use an exact amount of lye for the oils used so that if people didn't want to bother with “neutralizing” their soap, they wouldn't have to.
What does it mean to neutralize liquid soap, and why would you want to?
Because liquid soaps are often made with excess lye, the final soap can have leftover, unreacted lye which can also mean that it has a high pH due to the alkaline/basic nature of the lye.
If you plan to use the liquid soap for cleaning around the house, having an excessively alkaline soap isn't really a problem. In fact, it may even be working to your advantage.
If, on the other hand, you want to use your homemade liquid soap for cleaning your face and body, any unreacted lye, and extra alkalinity could lead to skin irritation. In the recipes I posted, I haven't found it to be a problem for me. I purposely calculated my soaps to not have a lye excess. That said, by calculating the recipe to be “exact,” we are playing in a zone where the final outcome of the soap can be easily swayed by a number of factors. Perhaps the scale you use isn't very precise or maybe my KOH has more or less water in it than yours and that affects how our soaps turn out. Even the same person using the same recipe with the same equipment can end up with different outcomes each time. You may end up with a cloudy soap, or you may end up with a slightly harsh one.
That's why a lot of people feel it is important to test the pH of your soap.
How to test the pH of soap
There are several ways to test the pH of your soap. Unfortunately, there is a lot of confusion about it because it is very difficult to get an accurate pH reading of soap at home, outside of a laboratory.
In the interest of seeing how alkaline my final soap pastes were, I bought pH test strips (they're very inexpensive and easy to use) and I used them to test the pH of the soaps. Because pH measures the concentration of hydrogen atoms in an aqueous solution, you will need to dilute the soap paste in distilled water to be able to test it with strips. Even when diluting the soap with distilled water, though, testing with test strips isn't necessarily very effective. If you don't add enough soap to your water, or you add too much soap to the water, you'll probably get inaccurate results. (And I haven't really found a set concentration that you should use for testing either.)
In the photo above, you can see that one of my liquid soaps tested to be around a pH of 8 and another tested to be around a 9. A neutral pH is 7, and anything higher than that is more on the alkaline/basic side, while anything with a lower number falls more on the acidic side. Most soaps tend to fall in the pH range of 9-10.
Let's take a closer look. I seriously doubt that the coconut oil soap is really at a pH of 8, because at a pH of 8 it would most likely be very cloudy already. I'm guessing it is higher than that, but since I've already been using both soaps without any problems, I'm not too concerned about finding the exact pH of these particular soaps.
Phenolphthalein is another indicator of pH that is often used by soapmakers, but that I haven't personally tried yet. It's a liquid that changes color depending on the pH of whatever you are testing.
More accurate testing can be done with electronic pH meters. You can find inexpensive electronic meters like this one, or more accurate probe pH meters that can test the pH of your soap. They are more expensive than the other alternatives, but if you plan on making more liquid soaps, or, especially if you want to make soap for gifting or selling, it's something you should consider buying.
There is another popular way of measuring pH amongst soap makers: red cabbage.
Even before I knew that testing pH with red cabbage was a thing, I accidentally “discovered” its pH reading ability on my own, and used it to my advantage to make a magical, color changing, natural food coloring.
I now know that my magical food coloring can also be used to test the pH of soap!
Basically it works like this: Take some cabbage leaves and blend them with distilled water, and strain out the leaves to get a purple juice. It will be more concentrated if you use the brightest, thinnest parts of the leaves. Once you have the cabbage juice, you can put a few drops on a small piece of your soap or soap paste. If it turns blue, your soap should be relatively safe to use without irritation for the most part. If it turns green, your soap is probably on the lye- heavy side, and you should consider “neutralizing” it if you plan to use it for face and body.
pH Balanced Soaps
This will probably be a controversial conversation, but I have to admit that I'm one of those people who doesn't believe the hype about using pH balanced “soaps” or detergents. I'm not even sure what “pH balanced” is really supposed to mean. Some pH balanced products have a pH in a more neutral zone whereas other pH balanced products are made to be more acidic. Of course real soap can't really ever be neutral or in the acidic range because the soap would break down and separate.
These products claim that using pH balanced products is important because our skin is more acidic, and that alkaline products will disturb our “acid mantle,” a covering on our skin that helps protect it. Most are detergents of sorts whose makers advise against using soap at all because soap falls normally falls between a pH of 9 or 10, more on the alkaline side of the spectrum.
First of all, I'd like to say that our skin isn't acidic, per se. Solids and oils don't really have a pH. You see, as I said above, pH is a measure of the concentration of hydrogen atoms in an aqueous (water) solution. Yes, our skin does tend to be covered with acidic secretions in the form of sweat mixed with oils and bacteria, but even if you remove this layer, your body quickly works to replenish it.
That doesn't mean, of course, that you shouldn't be careful about what or how you clean your skin. I don't think that one should overuse soap (or any cleaning agent) of any kind, be it “pH balanced” or not because you don't really want to disrupt the skin's protective layer any more than need be. My son has atopic dermatitis, and one of the first recommendations of the dermatologist was to not use soap or cleansers of any kind, not even the ones that are formulated for atopic dermatitis, on his skin any more than necessary. I tend to save my soap for washing my hands, or for using in places where bacteria can grow and cause odors, unless I've been working out in the garden and need to clean off dirt and grime. As for my face, I prefer bar soaps, like my activated charcoal soap, to liquid soaps because they are usually more conditioning because of the excess oils used in their formulation.
Let's get back to talking about pH, though…
I started studying the pH of soaps when I was developing a soap for my dog. Dog shampoos are usually a lot more expensive than human shampoos, claiming to have a special pH for dogs because the pH of dogs' skin is different than ours.
That said, when tested, the pH range of both shampoos for dogs and humans were all over the place. I'll get more into that conversation when I post my dog soap recipe, but I will say that I don't think that the pH is the main factor in if a soap will be irritating or not to our skin. Instead, certain ingredients will be more or less irritating to different people. I also believe that when it comes to homemade soaps, possible irritation isn't so much about the pH of the soap as it is if there is any unreacted lye left in the final product. That's why there are a lot of soap makers that solely rely on the “zap test” rather than check for pH.
The zap test is the idea that if you touch your tongue to a finished soap or soap paste, that you will feel a “zap” on your tongue if there is any unreacted lye in the soap. The proponents of the zap test tend to ignore pH, and focus on if there is unreacted lye or not, and how the soap actually feels when used. I tend to agree with them.
Getting back to pH again…
When it comes to skin, many people either use vinegar (acidic) or baking soda (alkaline) to help soothe skin irritations. (While others find that either can irritate their skin.) Having substances with a pH that is different from your skin, or non-neutral pH's coming in contact with your skin aren't going to necessarily harm it. On the other hand, if something that is acidic or alkaline enough comes in contact with your skin, it can cause skin irritations, or even burn you.
So while I prefer soap to “pH balanced” detergents, and don't think pH testing of soap is usually necessary, you will want to know how to troubleshoot any soap that is irritating to your skin. A soap that causes irritation is likely to have unreacted lye, and it is also likely to have a high pH. A soap with a pH far enough above 10 will very likely be irritating to most people, and that's what we're trying to prevent by “neutralizing” a liquid soap.
How to neutralize a liquid soap
Saying that you are “neutralizing” a soap is a bit of a misleading term, because the goal is not to get the soap into a neutral pH zone. Doing so would inevitably break down the soap. We are really just looking to bring the pH of the soap down slightly.
There are a couple of ways to help bring the pH of a highly alkaline soap down closer to a more neutral range.
Using citric acid to neutralize liquid soap
From reading the ingredients on Dr. Bronner's soap, it appears that their soaps are neutralized with citric acid.
As a very general guideline, around 4 grams of citric acid should bring down the pH of a Kg of soap paste by around .5. Of course, all of this is highly dependent upon how much water is in your water paste. Because citric acid is, well, acidic, it's very easy too add too much citric acid, especially with small batches. It's best to err on the conservative side, adding it little by little. Adding too much will first begin to make the soap look cloudy, and will later cause it to separate. You could, of course, check the pH between additions, but remember that pH readings can be inaccurate.
Unless I was worried that my soap was too alkaline because it was causing skin irritation already, I personally wouldn't do anything to it. In the case of an irritating soap, though, I would make a weak solution of citric acid and use it during the second dilution of my soap to gently lower the pH slightly. (Click on the link to read more about how I dilute my soaps.)
If you do see things starting to separate, stop adding the citric acid solution and allow the soap to sit for awhile before trying to combine everything back together again. If need be, you can finish diluting the soap with more distilled water.
Using borax or boric acid to neutralize liquid soap
While a lot of people are concerned with the safety of boron containing substances and avoid using borax or boric acid, it may be the most common way that liquid soap makers in the US neutralize their liquid soap because it is considered the easiest. Plus, it has the extra advantage of helping to thicken your liquid soap, as long as it's not made with coconut oil or other solid oils. Borax, when dissolved, already has a pH in an ideal soap pH range, so it's less likely to bring the pH down too far too quickly. Citric acid is a lot more acidic, and it's easy to go overboard really quickly.
Some countries in Europe have banned boron containing substances in cosmetic and soap use, so it may not be as common in Europe. It was recently brought to my attention, by a friend who used to use boric acid for killing ants and cockroaches, that boric acid is no longer sold in pharmacies because sale to the general public is now illegal here in Spain. I'm not sure if that is true or not, but it does appear that the pharmacy I once bought it from no longer is willing to sell it. Borax can still be bought from soap making suppliers and other online stores, though.
To neutralize with borax, dissolve 2 parts borax to 3 parts water. So, for example, you could dissolve 2 ounces of borax in 3 ounces of water. Many people say that you should add it when the soap is warm; others say it doesn't matter. I haven't done any neutralizing with borax, so I'm not sure if it matters or not.
I've seen suggestions about how much to add. One suggestion I've seen in several places is that you should add 1/2 to 1 ounce of the solution for every pound of soap paste. That said, you should keep in mind that the amount added really depends upon what you are beginning with, and how much you need/want to lower the pH. If your soap begins to get cloudy, you should probably stop adding no matter what you are using to neutralize your soap.
Last thoughts on pH and neutralizing soap.
This is one of those confusing areas of soap making with numerous opinions and conflicting information. Because I started making soaps as a “greener,” more biodegradable and less toxic alternative to commercial detergents, I also like to avoid using things like borax or boric acid, when possible. I also decided to calculate my liquid soaps without a lye excess, at the risk of possibly attaining a cloudier soap, to avoid having to do much in the way of pH testing and neutralizing, and also in the interest of simplification. I've spent hours upon hours researching the topic, but I still feel I have a lot to learn. This post is basically sharing my thought on the topic based on research and experimentation up until now, but I'd love to hear what you have to say. I hope that this will at least help you gain a better understanding of the topic overall while you experiment with liquid soap making. Of course, if the thought of making liquid soap scares you after reading all of this, you could start out with an easy, basic beginner bar soap instead. 😉