Should you be checking the pH of your soap? Why could it be important and how do you do it? And how and why should you neutralize your liquid soap if needed?
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 don’t find it to be as effective as a real liquid soap either.
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 also developed a couple of takes on a Dr. Bronner’s Liquid Castile Soap copycat recipe. )
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 be irritating to the skin. Soaps with unreacted lye will normally have a very 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 to a certain point. Highly alkaline and highly acidic products can be great cleansers. (Think vinegar and baking soda, or more extremely HCl or NaOH based drain cleaners.) Obviously, if it were too highly alkaline, you’d have to worry about it not eating away at delicate surfaces.
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 so they don’t 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 could end up with different outcomes each time. (Even temperature can be a factor.) 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.
Inexpensive pH test strips
In the interest of seeing how alkaline my final soap pastes were, I bought pH test strips to test the pH of the soaps. pH strips are great because they’re very inexpensive and easy to use. Because pH measures the concentration of hydrogen atoms in an aqueous (water-based) 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 may get inaccurate results. (And I haven’t really found a set concentration that you should use for testing either.)
When I first wrote this post, I showed the picture above. It showed that my coconut oil-based liquid soaps tested to be around a pH of 8 and the olive oil-based liquid soap tested to be around 9-10.
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.
Even at that time, I wrote this…
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.
In the end, I did re-test months later, and on my second attempt, I found it to read around 9 (just like the other soap). My thoughts on that? I feel that it was much more likely user error on my part when testing the first time around rather than the pH increasing with time. I probably had used too little soap paste in the water at the time of testing.
Testing pH with Phenolphthalein
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.
pH Meters
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 and other homemade cosmetics, or, especially if you want to make soap for gifting or selling, it’s something you could consider buying.
The problem with pH meters is that they usually have some upkeep so if you are only going to use it very sporadically, it may not be the best choice for you.
Testing pH with 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!
While I haven’t tried it yet, basically it is said to work like this: Take some cabbage leaves and blend them with a very tiny amount of 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.
Should you use pH Balanced “Soaps”?
This is a somewhat controversial conversation…
The argument for pH balanced cleansers
It can be confusing what “pH balanced” is really supposed to mean.
Some pH balanced products fall in a more neutral zone whereas others are made to be more acidic (like our skin).
Of course, real soap will never be neutral or in the acidic range because the soap would break down and separate at lower pH’s. Soap naturally has a higher, more alkaline pH.
When I first wrote this post years ago, I told you that I was one of those people who didn’t believe the hype about using pH balanced “soaps” (really detergents) for skin vs. using soap.
The claim for using pH balanced products is that our skin is more acidic and that alkaline products (like soap) will disturb our “acid mantle,” a covering on our skin that helps protect it. pH balanced products (like syndet bars or shower gels) use other surfactants instead that, unlike soap, can be adjusted into a more acidic range.
Is soap harmful to our skin?
First of all, I’d like to say that our skin isn’t really 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. Our skin, though, is covered with acidic secretions like sweat mixed with oils and bacteria. These form part of the acid mantle that protects our skin. If you remove this layer, your body quickly works to replenish it. That’s why, in most cases, we can safely use soap, and our skin completely recovers and becomes more acidic again soon afterward.
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 pH balanced ones formulated for atopic dermatitis, on his skin any more than necessary. I tend to save my soap for washing my hands, or for use in areas of the body where bacteria can grow and cause odors unless I’ve been working out in the garden and need to clean off dirt and grime.
Is pH the real factor?
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 isn’t going to necessarily harm it, but if something that is too acidic or too alkaline enough comes in contact with your skin, it can cause skin irritations or even burn you.
So, obviously pH does factor into whether or not something will be irritating to our skin, but, in most cases, most of us should be able to use soap on our skin without any ill effects because our skin recovers from that change in pH pretty quickly.
When should you choose a different surfactant over soap?
Despite what I’ve said above, I do think that there are times that you could (should?) consider other, non-soap, surfactants.
Infant skin is more delicate
When babies are born, their skin has to adapt from being constantly wet in the womb to the dry environment outside the womb. It takes time for their skin to develop the same protective covering as ours. A baby’s skin is more susceptible to irritation from changes in the environment and pH. Because their skin doesn’t recover as quickly as ours, I think it’s better to use another, less alkaline surfactant on their skin. That’s why I developed a pH balanced baby wash and shampoo using mild, natural surfactants for those who are looking for a mild cleanser for their children (or themselves).
Hair, shampoo, and shampoo bars
Our skin is a living tissue that can adapt pretty well to changes in pH, but our hair is a bit more sensitive to harsh changes. Our hair is mostly dead and doesn’t have the same sort of recovery mechanisms.
Because people are looking for a more natural solution to washing their hair, many have turned towards soap-based shampoos and “shampoo bars” that are really just soaps marketed for using to clean your hair. Most people will find, though, that eventually, soap will damage their hair. Its high pH will end up lifting the cuticle of the hair shaft, which can leave hair looking dull and leads to damage. That’s why a vinegar rinse is normally recommended after using a soap-based hair cleanser. The idea is that the vinegar will help reseal the cuticle.
Unfortunately, that may not be enough to prevent damage. I, personally, can’t use soap-based “shampoos” without my hair feeling like straw. That’s why I have shared a few shampoo recipes on the blog like a clarifying shampoo and a shampoo bar.
Laundry soap vs. detergent
Many have chosen to make soap-based laundry “detergents,” but soap-based cleaners may not be the best option for laundry. This is especially true if you have hard water at home. The minerals (mainly magnesium and calcium) in the water react with the soap to form an insoluble substance that can build up on the fibers of your clothes.
This buildup, or “soap scum,” can leave clothes looking dingy over time.
That’s why I usually use my homemade laundry soap for spot removal and use my homemade laundry detergent for daily washing.
Do you really need to test the pH of your soap?
While you normally don’t really need to know the precise pH of a homemade soap that you will be using for yourself, there are a few reasons/times that it may be good to have a ballpark idea of the pH of your soap.
Troubleshooting soap problems with a pH reading
If your soap is cloudy, it may be that it has too many unreacted oils or that the pH is too low, falling towards the neutral range. While a neutral pH might be better for your skin, soap can’t really be effective at a neutral pH. Instead, it has a tendency to fall apart back into its original components. This will leave you with a cloudy mixture that isn’t very good at cleaning.
The other issue with lowering the pH too far is that the mixture would be much more prone to microbial growth. Liquid soap normally has a high pH that makes it an inhospitable environment for most unwanted bacteria and mold. Soap with a higher pH is generally self-preserving.
On the other hand, if your soap isn’t as mild as you would have liked, it may have a pH that is too high. A soap that causes irritation is likely to have unreacted lye and is also likely to have a higher 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 liquid Castile 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 to 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 try making 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 a while 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 the 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 is 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.
If you’re wondering about how much to add, I’ve seen it said in several places 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 you are trying to lower the pH of your soap and it begins to get cloudy, you should probably stop adding whatever 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 questionable/controversial ingredients like borax or boric acid, when possible.
I 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 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 (not that I think it should), you could start out with an easy, basic beginner bar soap instead. 😉
Catherine
I am wondering what would happen to a liquid soap if it’s over fattened? I think maybe the ph would be “neutralized” at around 9.5? Would the sequestration time separate the extra fat and could we somehow extract only the soap?
Tracy Ariza
Hi Catherine,
The reason most people don’t superfat liquid soaps is that they will usually be cloudy and most people are trying to achieve a transparent liquid soap. If that isn’t important to you, you can definitely experiment with it! I’d love to know how it goes!
Jayeshkumar khemrajbhai Raval
Hello Dear..My Liquid Handwash soap is 7 PH..How is best or not???
Tracy Ariza
Hello,
If it has a pH of 7 it’s probably not a true soap and will be a wash of other surfactants. That isn’t a bad thing and works better for some people’s skin.
I have more information about other surfactants here.
Does it state the ingredients?
abera lobango
i wonder your actvity , i am abera lobango from ethiopia and i am chemistry laboratory assistance in wolkite university ( ethiopia) , now i wnat to start my own business in liquid soap prparation , but i have shortage of income what you can help me
Tracy Ariza
Hello Aberam
I don’t have any experience with selling soaps, so I can’t really help with that. You’d have to look into the applicable laws in your country to know what you’d need to do to legally sell your products.
Chanel
Can the paste neutralize naturally by sitting for a certain amount of weeks?
Tracy Ariza
Hi Chanel,
That’s an interesting question and would really depend on the recipe you are using. I purposely make my recipes so they don’t need neutralizing, but if the tiniest bit of lye were to remain, it may be able to neutralize with time.
I read, long ago, that with bar soaps, with time, a lye-heavy bar of soap may actually be able to “neutralize” itself. That’s because the remaining lye somehow reacts with the surrounding air. I can’t remember what was formed in the process, but it was one of the reasons given that soaps could become milder with time. (My first batch of soap, many years ago, was lye heavy. It stung my skin when I used it, but when I found a bar a year later, I was able to use it with no burning, so I was researching why that was possible.)
I’m not sure, but I would guess that a liquid soap paste could have a similar type of reaction with the surrounding air. As I don’t remember the exact reaction, I’m not sure if the difference in lyes used, KOH vs. NaOH, would make a difference.
As said, it’s mostly a guess based on what I’ve seen and read in a bar soap type application. It would also depend on how “lye-heavy” the soap is, to begin with.
Patricia Miranda
Hi Tracy! I am a beginner in this soap making and I am so happy I came across your website. I live in a hot country and the temperature here goes from 32° celsius during the day to 26°C at night. Is there anything in the procedure that I should change because of this? I am going to make your liquid soaps and bar soaps as well. Thank you!
Tracy Ariza
Hi Patricia,
No, you should be fine!
I actually love making soap in the summer and rarely make it in the winter. I don’t like having to melt solid oils to make soap, so it saves me a step. Plus, I like working outdoors and find it simpler to do in summer.
With liquid soaps, if you are using a slow cooker, it doesn’t really matter, but for bar soaps the heat is doing you a favor.
I will say that heat also helps move the process along a bit more quickly. That’s usually a good thing (unless you are trying to make some sort of elaborate pattern with a soap).
I’d love to be in a country where it is hot year round. Ha! I’m such a baby in the winter. 😉
Jessica+Tan
I’m not sure if it’s of interest but, i just added 5ml chamomile extract to 250ml liquid soap, it lowered the pH significantly with no separation, as it’s an extract i’m not worried about the preservative issue.
Tracy Ariza
Interesting. Actually, I’ve since talked with some cosmetic formulators that are always testing their products and they were telling me that the reason that you don’t need a preservative with liquid soap is really its higher pH. One told me that most products with a pH of 9 or above or 4 or below don’t need a preservative and can be kept up to a year without one. I found that quite interesting. It makes me wonder about what happens, though, when you lower the pH of the soap with other additives.
Maria
Hi Tracy, great post! I already made the liquid coconut oil soap and came across this post. If preservation is a problem, what do you think of using Grapefruit seed extract? As far as I know, it’s a natural preservative that can be used for cosmetics. For more information, please check this link:
https://www.elemental.eu/en/648-grapefruit-seed-extract.html
Tracy Ariza
Hi Maria,
I need to update this post! I’ve since talked with cosmetic developers who assured me that liquid soap doesn’t need a preservative because of its high pH. I was told that in a product with a pH above 9 or below 4, you should be fine to not use a preservative and keep it for up to a year.
As for the grapefruit seed extract for other products, it isn’t really a preservative, so it sort of bothers me that they’ve marketed it as such. It may help, and work in conjunction with other preservatives, but I definitely wouldn’t use it on its own. I remember reading about it years ago when I bought it to try to use to preserve a product myself, but ended up not using it after what I had read. Basically, it came down to the fact that it was able to preserve certain formulations, but it had nothing to do with the GSE in itself but was instead due to the preservatives used to help preserve the product in and of itself. The more I read, the less “natural” GSE sounded, and I doubted its efficacy, so I just didn’t use it.
Tracy Ariza
I actually decided to do a quick Google search and found this…
It’s interesting to see the comments section too. One reader claimed that for her it preserved a product that wasn’t touched for up to 2 months (based on her own testing), but she said it wouldn’t pass a challenge test (used before selling a product) and that if you touch the product, the mold spores, etc., would start to grow. It’s an interesting debate. I don’t have the ability to test for microbes at home, so I try to make sure I use preservatives with a good track record to stay on the safe side. 😉
Nasria
Halal Homemade Laundry/Dish Liquid Soap
Ingredients: One Jar of 84 fl oz Kirkland Organic Virgin Coconut Oil(approximately= 80 ozs)
KOH potassium Hydroxide(Lye) 19.98 oz
Water 66.65 ozs
Melt the oil and pour in a large stockpot steel container to cook on stove top for faster process. Mix lye in separate plastic or glass or steel container. Once it is clear add it to oil. No need to wait for it to cool down. Stick blend till hardens enough. stick blender does not work anymore. change to wooden strong thick spoon. Put the soap mixture on the stove top on low to medium heat. Stir occasionally for an hour or so. once the paste has started to become more Vaseline like or almost clear add water to dilute. I add about 4 gallons to dilute. Cook for half an hour and turn off heat. Let it cool down to warm touch and add essential oils of your choice. I put 1.5 oz of lemongrass essential oil and 1.5 oz of Eucalyptus essential oil for fragrance. If you add essential oils in hot liquid they will mostly evaporate. That would be waste of perfume and money. Buy 5 gallons water bottle with spout and large opening from any water selling store and store your liquid soap in it. I put my bottle on top of washer where I can easily dispense liquid soap right into front loading machine. My cost $20 including essential oils for very concentrated 5 gallon soap with out any harsh unnecessary chemicals.
Enjoy this free recipe from professional soap-making software.
Tracy Ariza
Thank you, Nasria for sharing your recipe. I have several up on the blog too, if you are looking for other options. 🙂
MissE
Hi Tracy, love this! I was wondering if you got to try this for lowering pH of your liquid soap? I want to use something natural too. Also, have you ever added botanicals and if you did, at what stage would you suggest adding it and would it then need preservatives?
Thanks!
Tracy Ariza
Hi MissE,
I’ve actually been studying this again lately, and have wanted to get around to updating this post with my new thoughts.
The main concern I have with lowering the pH of soap is the problem with preservation, that you mentioned. I talked with a cosmetic chemist who said that liquid soap doesn’t need a preservative because it has a high pH (above 9). If you start lowering the pH too much, not only could it fall apart, but we’re starting to head into the problem of needing a preservative.
When adding botanicals, we have a similar problem. You could probably get away with adding some, depending upon what you are adding, but we start heading into a problem territory for preservatives. Botanicals are notoriously difficult to preserve, especially with the more natural preservatives, and unless you are actually testing your products, it’s difficult to know how safe they will be. For now, I’m quite happy with the liquid soaps, as is, with the addition of already preserved store bought essential oils and extracts.
For pH issues, I’ve been experimenting with natural surfactants and will write more about those very soon!
MissE
Hi Tracy, thanks for taking the time to respond at length. What kind of extracts do you have in mind? I was thinking of maybe steeping a handful of dry rose petals or something in the water with the soap paste but maybe not? I really don’t want to wade into preservatives (yet) so I think I’ll just back off.
Your thoughts are valuable!
Tracy Ariza
Sorry- I overlooked this!
Well, any time you make an infusion like that you are raising the risk of it not being properly preserved. That isn’t something that would change the pH really, probably, so you may be fine relying the on the high pH of the soap. The problem is it’s impossible to know for sure.
If you wanted something with roses, I’d suggest using rose water as part of the water to dilute the soap instead.
If you want to infuse real roses into something, I’d probably infuse dried rose petals into the oils for making the soap. (Although at that stage you could also make a rose tea to use in that stage without problems.)
It’s the diluting stage that I see the most problematic. I cringe when I see body wash recipes that mix milks with other botanicals and use no sort of preservative. I’m not sure how long those sorts of things can really last. You can only rely so far on the pH of the soap, I think. I prefer to err on the side of caution.
MissE
I have to agree! Can I email you for more of this conversation?
Tracy Ariza
That’s fine, but I’d prefer to discuss here so that others can benefit from the conversation. 😉
MissE
Ok. 🙂
Hafiz Kadir
A very comprehensive + authoritative explanation about the process. Way to go,Tracy!
Tracy Ariza
Thanks, Hafiz. 🙂
Claudia
I can’t thank you enough for all your knowledge, time and information that you share. Keep up the great work!
Tracy Ariza
Aww, thanks Claudia!