amount of Lye

[Marilyn Norgart]

I just used a different calculator and found I am using .16 less lye then I am supposed to be. I haven't noticed anything wrong with my soap but it got me to wondering what happens when you don't use "quite" enough lye. does it structurally change your soap. I did have the right amount written down but had scratched it off and wrote the lesser amount

 

[earlene]

You just have a slightly higher superfat. But 0.16 grams, if that is what is is, wouldn't be much unless it's a really tiny batch.

 

[Marilyn Norgart]

its .16 oz

 

[Andrew]

different calculators occasionally have different SAP values for oils. Your soap will be slightly more superfatted without the lye, but not by much. If you like it then i would keep doing it that way.

 

[jcandleattic]

Calculators use an acceptable SAP range and it's very rare any 2 calculators will have the exact same numbers. For consistency this is why it's good to pick a calculator you like, and stick with it.
In the scheme of things it really isn't going to change your soap so significantly that you will probably even notice. As others said. it will either increase/decrease your superfat, (depending on the calculator used) but by less than a single percentage point.

 

[amd]

It may also depend on your oil. I believe that the SAP is an average because the FA profile of soaps are averages too, as they will vary by growing season and/or mfg methods. As jcandleattic said above, it really isn't going to change your soap.

 

[Rune]

That's why it is so important to use at least 2% superfat, since your oils will have different actual sap values than the middle value you get from the lye calculator you use. You need superfat as a safety buffer, or you risk lye heavy soap.

 

[DeeAnna]

Well, yes and no, @Rune. Since most, if not all, soap calculators assume the NaOH purity is 100%, there's also a safety margin built in that's the difference between the assumed 100% purity and whatever your NaOH purity really is.

 

[Rune]

Yes, you are absolutely right about that @DeeAnna I have used superfat in the minus range once or twice because I had old lye I knew was not very pure anymore (it was lumpy). But I know how to test lye purity thanks to your Youtube video on the subject.