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How can I lower the PH in cold processed soap?
I am not a chemist. I am a handmade soap artisan that makes soap using the cold processed soap method; oils, butters, fats mixed with lye solution. My soaps have a PH of 9-10. I want to create a soap that has a PH of 6.5 to 7.5. What can I use that is safe to lower the PH in my soaps? Someone mentioned citric acid but cannot tell me how much to use. if I use too much citric acid the soap falls out of solution. Can you tell me how much citric acid to use per pound of oils or give me another option for lowering the PH? Your advice and input is greatly appreciated. Thank you.
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35 Replies
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If you lower the pH of a saponified soap this low (6.5 to 7.5) you will no longer have soap as it will cause the product to fail. So the short answer is you can’t.
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This is one of the reasons we have synthetics.
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There’s a trick to (sort-of) doing this, that depends on how pH is measured. Since pH only exists in an aqueous solution, most people measure the pH of a soap by melting/dissolving 10% of it into water or water/alcohol. If you mix your citric acid granules with a non-saponifying oil, and then stir that mixture into your soap just before you pour it, what you wind up with is high-pH soap that has undissolved granules of citric acid in it. Now, here’s the trick - when you dissolve that soap into water to measure the pH, the citric acid dissolves also, lowering the pH down to 6 or 7 by the time the pH is taken.
I’m not sure how much citric acid you should use, you’ll have to determine that yourself by experimentation. I also don’t know how badly this will affect the lather or the stability of the soap while in use, you’ll have to test that yourself also.
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@Bobzchemist - could it be a way of making preservative free cosmetics?Increase the pH then use acid granules or encapsulated acid which dissolves when rubbing on the skin to get a skin friendly pH.
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Bobzchemist, thank you for your speedy response.
I test the PH of my soaps with a litmus strip by creating a lot of lather after the oils have saponified. I test it after I take it out of the mold, usually 24-48 hours later. I’ve consistently gotten a PH of 9-10 which is what we want in handmade soaps.
All the oils, butters and fats I use are able to be saponified. There is a method of making soap, the hot processed method, where we can add oils after the majority have been saponified. ths is done to super fat the soap, to make it more moisturizing, but I do not make soap using that method.
What are your thoughts on adding citrix acid to the lye and water mixture and then adding that to my oils and butters? Will this cause the lye not react properly with oils and butters. Will it prevent saponification?
I’ve used a recipe that suggests .5 ounces of citrix acid for 50 ounces of oils. I dissolved the ctrix acid in distilled water and added it to my oils and then added the lye water. The mixture has saponified. The PH reads not quite 8 so I’m assuming it is about 7.5. I’m hoping that as the soap cures the lye will neutralize and the PH will drop.
I will try your suggestion of mixing the citrix acid with oils then adding my lye water… Thank you.
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Microformulation - how low can I lower the PH before the product fails? Dog shampoos/soaps are about 7-7.5 PH. Is this because most are liquid soaps and synthetics are being used?
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There is a lot more information on this topic in the Soap Making Facebook groups. One woman once claimed to have reduced her saponified soap to 7.5 but when challenged she could not repeat the process.
Pet shampoos using saponified soaps and synthetics can be dropped further.
I would have to defer the question. Soaps were exempted from the Cosmetic Act and like many Chemists my knowledge is more academic than practical. There are several soapers in this forum and I am sure that shortly they will weigh-in.
As @Belassi rightfully points out, the pH issues with soaps are one of the reasons that surfactants are so predominant in the industry.
Regardless, if you are going to even attempt this. I would recommend getting a pH meter, not relying upon pH strips.
You can’t add the Citric acid to the NaOH solution and then expect any significant saponification. They defies the simplest Chemical concepts.
Keep in mind that @Bobzchemist‘s method is a bit slick and arguably doesn’t give you a true pH. No offense Bob, but I read between the lines and I think that was also in the back of your mind.
And again “preservative free” comes up. Proper appropriate preservation trumps any “preservative free” method in safety. As a general rule, customers will appreciate a safe product over a trendy yet unsafe Marketing gimmick.
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Soaps are excluded from cosmetics as long as they do not make any cosmetic claims. Once soap makers make claims such as moisturizing, etc.. we move into soaps being labeled as cosmetic.
so what I get from your post is that if I use a synthetic can drop the PH. I don;t want to use synthetics.. there must be another way. Perhaps pushing the PH to the lowest limit?
those meters are hit or miss for us as well..
Fb groups are more ignorant about this than I am. That’s why I came here. I’d like to understand, as much as my less than elementary chemistry mind can understand. Thank you.
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Why don’t you want to use synthetics? It just is not possible to use cold process soap at the pH you desire. Or you can waste the next 6 months and a lot of material proving that… There are many, many synthetics with properties that make saponified soap look primitive. I make cold process soap but I leave it in the state it was intended. When I want performance at a desired pH, I use synthetics.
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The meters are much better than strips. If it is a price issue it simply is so. The litmus strips do not have the proper range.
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Money is not an issue. My soaps are not primitive looking. LOL!! I just want a soap that has more natural ingredients. I’m trying to create a shampoo bar and that’s why I’d like a slightly lower PH.
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I meant money in regard to meters. I have never heard a great argument of strips over meters unless someone was trying not to spend the money on a meter. A pH Meter with calibration capabilities is the way to go and arguably preferred under cGLP.
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What is your definition of “natural”? For example, it’s highly unlikely that the Lye you use is natural. It’s synthetically produced.
I agree with @Microformulation. pH strips are not something a serious formulator would use. They are not accurate enough & don’t comply with GMP.
Mixing Sodium Hydroxide with Citric Acid will produce Sodium Citrate which will interfere with the saponification reaction. It’s not a good idea.
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Then the synthetic lye and fragrance oils are the only things I use that are synthetic. I’m trying to create as natural a product as possible using chemical free ingredients.
Many artisan soap makers are just regular people from all walks of life. Many are housewives. Some were taught how to make soap by their family members. I can’t speak for all but I am as serious as I can be about producing a good product. I want to and need to understand more especially about the chemistry that’s why I’ve chosen to enter the lions den here. I’m just looking for answers to things I do not understand. I want to make a shampoo bar of soap with a lower PH.
Handmade soap artisans use several methods for testing their soaps to make sure the lye is neutralized. there’s the “zap” test which is really antiquated; soap makers touch their tongue to the soap and if they get a zap the lye is not neutralized. PH test strips which are not 100% accurate give us a number. Phenolphthalein which changes color but does not give us a number is used by some but it is poisonous and then there is red cabbage, which also does not give us a number, it just changes color. Some have reported using a PH meter and claim it is not very accurate. I have no doubt that the issue is user error.
My query is about using citric acid to lower PH. I want to go as low as I can before the soap falls out of solution. There must a threshold of some sort. I gather from these responses that no one here really knows the answer so I will experiment and see how far I can go before my mixture falls out of solution.
Do not mix lye directly with citric acid. Noted.
Thank you all for your time and responses.
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One last thing is that handmade soap artisans are not regulated, unless we make cosmetic or medical claims. we don’t need to follow cGLP or GMP regulations. What are those? We don’t even have to put ingredients on our labels if we are just making soap for cleansing.. there’s very little oversight from the FDA for handmade artisan soaps.
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You can best find out about Good Laboratory Practice and Good Manufacturing Practice via Google.
Google is your friend.
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Even though it is not a Cosmetic, I would suggest if you are making a retail product you follow cGMP. This would be a good idea even if you are making widgets.
Your position is reckless and dangerous otherwise!!!!
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I see that you are trying to make a soap based shampoo bar.
Remember that soap produces an unpleasant precipitate (scum) in hard water which, trapped in hair, can be very difficult to remove and give very much unwanted dullness, and a lack of a feeling of cleanliness.I notice that a large portion of the USA has hard water. Not everyone has a water softener.
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I did say that my method was a trick, right? It’s a gimmick - a way of saying that you have a pH-neutral soap without actually having a pH-neutral soap.
I think I need to get into basic chemistry for a bit so I can explain. “Natural” soap is what you get when you react a plant or animal oil (triglyceride) with a strong base, usually Potassium and/or Sodium Hydroxide (Lye). It’s a two-step reaction. First, the triglyceride gets broken up by the base into 4 pieces - 3 fatty acid molecules, and 1 glycerin molecule.
The second step is the reaction between the fatty acid and the base (lye) to make a salt (soap). The problem you are having is that this step is reversible - if the pH of your soap drops much below 9-10, the reaction goes the other way, and it turns back into fatty acids. Fatty acids are just pieces of oils, remember, and they do not clean at all.
This is why we keep telling you that you can’t do what you’re trying to do. At a pH of 6.5 - 7.5, it is not chemically possible for soap to exist. It simply can’t be done, not by you, not be me, not by anyone.
If you dissolve too much citric acid in anything during your soapmaking process, you will destroy your soap (as you’ve seen).
You are correct when you say that we don’t know the answer to how much citric acid you can use before your soap reverts to fatty acid. That’s because the answer is different for every single oil and combination of oils out there - they only way to find this answer out for your particular formula is to experiment with different acid levels yourself.
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By the way, there are some good and knowledgeable Facebook Soap groups that cover this. The posters have more experience and practical knowledge in these areas than you give them credit for or likely have yourself at this point.
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Here is the soap reaction that @Bobzchemist was talking about. This reaction can go to the right (to produce soap) or to the left (to produce a triglyceride). When you lower the pH you make the reaction go to the left. -
This is what has prompted my query. A very well known reputable and established soap maker wrote this. In the article the claim is that the soap she gives a recipe for ends up with a PH of 7.5 because of the addition of citric acid. She closes by suggesting the use of a vinegar rinse for the scum build up, also quoting a very reputable source in the cosmetic chemistry industry.
https://www.soapqueen.com/bath-and-body-tutorials/cold-process-soap/sudsy-shampoo-bars/ -
Because of my experience with many fb groups saying things like lye heavy soap will neutralize over time, etc.. I’d rather come to a chemist to get the facts.. Soap making is fairly unregulated, as I’ve mentioned. I do not want to be reckless or lie about anything I do. I’d rather not create it if it will cause damage or harm. so based on all these responses I have to say that the the claims in the article of a shampoo bar having a PH of around 7 are a farce. thank you for clarifying this for me.
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When did SoapQueen become “a very reputable source in the cosmetic chemistry industry?” It is a blog featured by Brambleberry with no citations and no credentials.
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soapqueen has always been one of the reputable sources for handmade soap crafters. Yes, she blogs and makes many instructional videos for soap crafters as well as other beauty aids.
I got my answer from people who took the time to explain and for that I am thankful. You are misinformed if you think the fb groups have the depth of knowledge that cosmetic chemists have. Very misinformed….
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