liquid soap ph

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visar0990

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I've been experimenting on liquid soap lately, but there are a few things I'd like to know which I haven't been able to find anywhere on the internet, and I suppose you could give me some useful information on the subject.

I know that in handmade liquid soap either citric acid or boric acid is used in order to neutralize any unreacted potash that may be present at the end of the process and reduce the pH. But even so the pH still remains high in the finished product. What I would like to know is whether it is possible to obtain a pH level of around 5.5 starting from a handmade potash liquid soap, and if so, how. If not, what is the minimum pH value that can be obtained?
 

The Efficacious Gentleman

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The pH of any real soap that is not lye heavy will depend on the oils used to make it. One recipe can have a pH higher or lower than another. Which is why pH is actually not important in soap making.

The important thing is excess lye - more lye than is needed to saponify all of the oils.

You can have a pH of 9, 10, or even 11 or 12 and the soap can be totally safe and lovely. As long as there is no excess lye.

Edit to add - you will never get to pH 5.5 with any lye-based soap. It will always be alkaline, not even neutral. Acidic is totally out of the question
 

DeeAnna

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"...What I would like to know is whether it is possible to obtain a pH level of around 5.5 starting from a handmade potash liquid soap..."

Absolutely not possible. Susie is correct.

"...If not, what is the minimum pH value that can be obtained?..."

The minimum pH for a lye-based liquid soap is the lowest pH that doesn't cause the soap to break down and separate. That will typically lie in the pH range given by The Gent, depending on the fatty acids in the soap.

Some people have attempted to make a soap around pH 7, but they have to add surfactants to keep the product looking and functioning like liquid soap. By that time, it's not really a lye-based soap anymore; it's a syndet (synthetic detergent) mixture.

The term "potash" as used in a soaping context, means potassium carbonate (K2CO3). Most modern liquid soap is made with potassium hydroxide (KOH). KOH is more correctly caustic potash, just as sodium hydroxide (NaOH) is caustic soda.
 
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visar0990

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Thank You everyone.

Can you please explain me,is there a way to know if I have excess Koh on my liquid soap?
 

Susie

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When the soap is in paste form, you wet your finger, rub it on the paste, then touch it to your tongue. If you get something akin to a shock from a battery, you have excess KOH. This is known as the zap test. It also works on bar soap. You can also simply touch the tip of your tongue to the soap paste.
 
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