There are diagrams out there for other pure soaps. I wanted diagrams that were really clear and as easy as possible to understand for my posts in this thread, which is why I chose the three that I did.
I found a similar phase diagram for sodium stearate (the NaOH soap of stearic acid) today. The basic phase changes for sodium stearate are quite similar to potassium stearate. The main difference is the sodium soap needs the temperature to be 10 C to 15 C higher to shift from solid to gel.
I wanted to also add that the pure soap content in my recent recipes is about 80% of the total batch weight when I use 33% lye concentration. If I would soap with a 28% lye concentration (aka "full water" for a soap made with a blend of fats), the pure soap weight drops to about 75%. If you look at the "blue line" examples in the diagrams above, those blue lines are at the 80% pure soap mark. If you use your imagination to shift the blue line to the 75% pure soap mark, you can see why this one single change -- a change in lye concentration from 28% to 33% -- could mean the difference between a batch of soap gelling during saponification versus the soap not gelling.
Does that mean the soap will be soft and spongy if the soap gets hot but doesn't actually gel? My experience says it won't, as long as the soap can heat up to a decently toasty temperature and can cool down naturally. If the soap stays unusually cool during saponification -- say your soap ingredients are really cool, or you put the soap in front of a fan or in the fridge, or the house is winter-time cold -- then yes the soap may not get warm enough and may stay soft and/or spongy after saponification is over.
I found a similar phase diagram for sodium stearate (the NaOH soap of stearic acid) today. The basic phase changes for sodium stearate are quite similar to potassium stearate. The main difference is the sodium soap needs the temperature to be 10 C to 15 C higher to shift from solid to gel.
I wanted to also add that the pure soap content in my recent recipes is about 80% of the total batch weight when I use 33% lye concentration. If I would soap with a 28% lye concentration (aka "full water" for a soap made with a blend of fats), the pure soap weight drops to about 75%. If you look at the "blue line" examples in the diagrams above, those blue lines are at the 80% pure soap mark. If you use your imagination to shift the blue line to the 75% pure soap mark, you can see why this one single change -- a change in lye concentration from 28% to 33% -- could mean the difference between a batch of soap gelling during saponification versus the soap not gelling.
Does that mean the soap will be soft and spongy if the soap gets hot but doesn't actually gel? My experience says it won't, as long as the soap can heat up to a decently toasty temperature and can cool down naturally. If the soap stays unusually cool during saponification -- say your soap ingredients are really cool, or you put the soap in front of a fan or in the fridge, or the house is winter-time cold -- then yes the soap may not get warm enough and may stay soft and/or spongy after saponification is over.
Last edited:
