Grandmother & Soaper
- Apr 30, 2016
- Reaction score
- Western Illinois, USA
I don't quite understand? Batch size is directly proportional to needed amount of liquid, so the vinegar as %PPO is the same, regardless of batch size, and so is the SF increase.
You are right, and I even thought after posting that I should go back and fix that, but I didn't because it was midnight & I was too tired.
What I left out that is more important in relation to why it isn't worth the bother for me to do the extra calculations is that I use my masterbatch lye solution [50%], so what I add as additional liquid has very little impact on superfat.
Even while traveling, I bring my masterbatch lye solution along, so I rarely make up a whole new solution while on the road. I do often have to buy drinking water and I find that distilled water is often cheaper than most bottled drinking water, so that's what I buy if I am also making soap.
I've done the calculations in the past, and the SF difference really is negligible in this situation (using mb lye.)
For example, I have done this many times and a 500g of oils batch using mb lye @ 0% SF & [33% Lye], the additional liquid needed is 69 grams. If I put 69 grams of vinegar instead of water, the difference of actual NaOH is only 2.5 grams (5 grams of the masterbatch, which is half water). 2.5 grams of NaOH is not going to change the SF enough that I need to bother with adding a little extra. (It actually only increases about 3.5%, but as far as I'm concerned, it is not noticeable). If I'm off a gram or two when I weigh out my oils, I don't sweat it, neither do I for a gram or two of water. So the gram or two of NaOH is not going to make or break my soap IMO and IME.
Call me sloppy, but I don't run a lye purity test everytime I make soap either. And we all should know that there are variables regarding lye purity and scale accuracy that impact SF as well, which is why I don't feel that a gram or two is really something to worry about.
IF I was faced with completely replacing vinegar for water in my lye solution, I would not because I did that once, and the soap came out so brittle that I decided never to do that again. It was the only time I made up a fresh batch of lye solution using only vinegar and no water at all.