Confused by Neutralizing Liquid soap

[Back2soaping]

Hello everyone! I am making liquid soap for the first time and have a question while reading Jackie Thompson's Liquid Soapmaking book. Going through her basic paste method in chapter 3, she says to check for neutrality in the cooked paste with phenolphthalein in step 11, and then neutralize with a citric acid solution when diluting the paste in step 13.

Why do you need to do this twice? If the paste tested ok in step 11 (meaning full saponification and no excess lye), I don't understand you need to neutralize the diluted soap with citric acid in step 13?

I thought once there is no excess lye in step 11, the soap is safe to use - or is this not the case? I am so confused and hope someone here can clear this up. Thanks in advance!

 

[Kcryss]

Not sure why there would be instructions to add Citric Acid to LS when diluting. Adding citric acid will drop the PH and cause the soap to break. @DeeAnna has an article here on adding acids and why you should not do it.

 

[AliOop]

Jackie Thompson's recipes start with a lye excess to ensure a zero SF, which is to ensure high clarity. The diluted soap then has to be neutralized with a citric acid solution to eliminate the excess lye. I don't know why she recommends doing that twice. I find the whole thing tiresome and simply formulate with 0 SF to start.

 

[DeeAnna]

I agree with what everyone else has said. If the soap tests "neutral" then there's no reason to further neutralize. If the soap tests alkaline, then more neutralization is required.

I don't have Thompson's book so I don't know how she presents this information. From what the OP is saying, however, it does indeed sound like the instructions are not as clear as they should be.

****

I am extremely skeptical that phenolphthalein, as liquid soap makers typically use it, really shows whether the soap has a true excess of lye or not. This indicator changes from colorless to pink about pH 8.2 if used correctly in a dilute solution. There is no way soap can be actual, functional soap at pH 8.2. The pH of skin-safe soap -- soap with no lye excess -- ranges from around 9.5 to 11.5.

But I'll step off my soapbox now

 

[AliOop]

I'll step off my soapbox now

Pun intended, right?

 

[Sunibee]

Not sure why there would be instructions to add Citric Acid to LS when diluting. Adding citric acid will drop the PH and cause the soap to break. @DeeAnna has an article here on adding acids and why you should not do it.

Thank you .. can I add a diluted NaOH instead of Koh as I am out of it ..

 

[AliOop]

Thank you .. can I add a diluted NaOH instead of Koh as I am out of it ..

This thread is talking about neutralizing LS that has a lye excess. If that's what you are trying to do, then you need a citric acid solution, not a lye solution.

However, if you have the opposite problem from the original poster (i.e., an excess superfat that is not diluting well), then yes, you could add a little bit of diluted NaOH rather than diluted KOH. Just know that NaOH is going to thicken your LS somewhat, and that too much could result in snot-like strings.

For future, when you are asking a question that is significantly different from the original post, it's best to start a new thread. That way, people aren't confused, and your question will get more attention, since things can get buried in threads.

 

[Susie]

Jackie Thompson uses the

I agree with what everyone else has said. If the soap tests "neutral" then there's no reason to further neutralize. If the soap tests alkaline, then more neutralization is required.

I don't have Thompson's book so I don't know how she presents this information. From what the OP is saying, however, it does indeed sound like the instructions are not as clear as they should be.

****

I am extremely skeptical that phenolphthalein, as liquid soap makers typically use it, really shows whether the soap has a true excess of lye or not. This indicator changes from colorless to pink about pH 8.2 if used correctly in a dilute solution. There is no way soap can be actual, functional soap at pH 8.2. The pH of skin-safe soap -- soap with no lye excess -- ranges from around 9.5 to 11.5.

But I'll step off my soapbox now

Jackie Thompson uses the old lye excess then neutralize method some of our members are fond of. Thank you again for bringing sanity to this situation.