I only tried making soap at home once, and it didn't go well, so I've stopped ...
The problem I am pondering is possible misinformation on all of the soap making lists.
Most of the people just trust to the lye tables
Might work adequately well, for very specific, limited recipes. Probably best for fats like olive oil, which have a very defined composition, and less good for animal fats, especially mixed sources.
or at most, tongue the finished soap for the so called zap test.
A hah ha ha. Oh wait, you're serious. Yikes.
The more advanced makers put a drop of phph on their bars and if it does not turn pink it is deemed safe to use or sell.
Hmmm ... no, that's not what I've suggested in this thread.
My experience is that it almost never turns pink even if the pH is over 10 on a meter unless stirred into the bar with a bit of water and then it almost always does turn pink.
Fresh soap is rarely under 10 and frequently takes days or weeks to get there if ever.
Now this I like hearing, I'm glad you've put effort into learning something, and applying it to your hobby.
Not being a chemist, I am reluctant to point out to the nice ladies that their tests are invalid the way they are doing it.
Suggestion: Wait until they complain they are being burnt. Then suggest they should dissolve their soap in water and check its pH with a meter. Then you will have helped them, without challenging their preconceptions.
As it turns out pH 10 is perfectly safe but they all claim their soap is nominally pH8 because it passes the phph test.
Erm. No. That's not correct.