Catherine Failor's book on liquid soap making promoted the method of making lye heavy KOH soap paste and then neutralizing the excess lye with borax or citric acid. Having compared the method in Failor's book with those in old soap making manuals, I have the strong impression that her method was adapted from the classic process of making "boiled" soap using fats and alkali of varying composition.
With the boiled method, you calculate the fat and alkali weights as best you can, cook the soap until it is as saponified as you can get it, zap test the finished soap paste, and then add small amounts of lye or fat as needed until the soap is sufficiently close to neutral (by this I mean no excess fat and no excess alkali.) It takes time and patience to get it right.
Failor's goal, as far as I can tell, was to make a lye-heavy soap and then neutralize the excess alkali. She could have added a little fat to neutralize the excess lye, but she wanted the soap to be as clear as possible, so instead she neutralized with borax or citric acid. It takes patience and know-how to neutralize excess lye this way -- it's pretty easy to make a mess if you get in a hurry or don't really understand what you're doing.
Many tutorials based on this "make lye heavy soap and then neutralize" method say to add X amount of citric acid solution (or borax solution) to the paste. You simply can't do that. Every batch is going to be a little different so the amount of acid required will vary. Many tutes fail to make that point really clear, so I think a lot of budding liquid soap makers have given up in frustration.
I'm with you all -- I'd rather make liquid soap with a slight superfat and be done with it. With this one change, KOH liquid soap making becomes about as easy as making NaOH bar soap, once you get a little experience.
Another issue I have with Failor and other liquid soap makers is that they cook the paste for hours. That's not necessary either. But that's another soap box that's best left for another thread and another day.
