Wrong weighting of lye

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musmar.firas

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it came to my attention that one of the soaps i did is not quite right.
first I thought its only soda ash, but later i found its too solid (breaks too easily) and when tested through PH strips, i found it heavily Basic chemical.
so I'm guessing that i made wrong weighting for the oils vs lye.
Since I don't know what exactly the wrong ratio, I decided to make rebatch for it and add oils through hot process.
but how much oil i should add and what which oil?
since i though its trial and error experiment, i decided to add cheap oil (corn oil) and to add 100 gram per time.
I added oil 3 times, 100 gram first two times and 60 gram last time (added 60 grams because the bottle finished ;) ).
it took 3 hours to cock it through microwave starting from melting till last pour of oil.
still not sure if i got it right or not.

I liked to share my experience and wish if anyone can advise me if I should have done it in different way ?
 

ResolvableOwl

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Hmm. For a first, you need proper bookkeeping of your recipes and comments. Store them in a safe place, or print them out and store them together with your soaps. You just noticed how things become needlessly complicated when you don't.

Your process of repeated oil addition might lead to somewhere, but I'm not sure if it's worth that hassle. First, be sure that you can rely on measuring pH correctly, or (better) know that your soap has a positive zap test.
Then, you'll have to be sure that, after you've added the corn oil, it got fully saponified. I'd guesstimate that one hour after the last oil addition is the minimum time for the next reading.

Easier than to find out about lye excess the hard way, you might just salt out the soap.
 

musmar.firas

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Hmm. For a first, you need proper bookkeeping of your recipes and comments. Store them in a safe place, or print them out and store them together with your soaps. You just noticed how things become needlessly complicated when you don't.

Your process of repeated oil addition might lead to somewhere, but I'm not sure if it's worth that hassle. First, be sure that you can rely on measuring pH correctly, or (better) know that your soap has a positive zap test.
Then, you'll have to be sure that, after you've added the corn oil, it got fully saponified. I'd guesstimate that one hour after the last oil addition is the minimum time for the next reading.

Easier than to find out about lye excess the hard way, you might just salt out the soap.
Great Information.
it just came to my mind now, what if i added vinegar to the rebatch, wouldn't that neutralize the extra lye?
 

DeeAnna

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How do you KNOW the soap has excess lye? A zap test or a test for excess alkalinity (NOT a mere pH test) is the proof you need. You have not done either one.

And even if the soap has excess lye, you don't know how much excess there is. How can you make an intelligent decision about how much fat or acid to add?
 

ResolvableOwl

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Yes, but only if you use the right amount. Too little and some of the lye would remain. Too much, and the vinegar would attack the soap and liberate free fatty acids, that have a very unpleasant skin feel, ruin lather, accelerate rancidity, and (in case your recipe contains coconut oil) smell bad.

So if you know how much lye you have too much in your soap, vinegar (or citric acid, or even stearic acid that will be converted to soap itself) is a fair way to make your soap safe for use. But if you know this number, you could as well use oil for that.


ETA: @DeeAnna is right (and was a mer second quicker than me ;)). The only way to find out said amount is titration. In fact, when you are carrying out your corn oil additions and make proper tests on excess lye (including reaction, cure and zap test) after each step, you are titrating. You will find out the amount of excess lye – but for a batch that doesn't need to be neutralised any more 🤷‍♀️.
 
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