The hot-process method differs from cold-process in that external heat is applied
after the fats and oils are mixed together. Instead of allowing saponification to take
place during the molding stage – which takes a long time – saponification takes place
before the soap is molded. The hot-process method was commonly used when the
purity of the lye soap-makers were able to obtain was in question. Also, if you want
to use a natural lye solution, such as potash, instead of 100% lye, hot-process is the
best method to employ. This is because the hot-process method requires less exact
measurements than the cold-process method, because saponification is “forced”
instead of taking place on its own. Therefore, it is unnecessary to know the exact
concentration of lye in the mixture, so less than pure lye can be used.
In the hot-process method, the mixture is heated over a double-boiler, or in a
crock-pot, during the trace stage, and the soap is, quite literally, “cooked” to achieve
more rapid neutralization. The crock-pot method is the easiest because the
temperature is easily regulated, and the soap is less likely to burn. The amount of
soap you can make will vary based on the size of your crock-pot, but ideally, you want
the crock-pot to be about half full. Any less, and the soap may burn; any more, and it
may boil over if the temperature is too high. The ideal temperature will vary based
on the oils you use, and by each individual crock-pot. Just like stoves, some operate at
a higher temperature than others. If you are unsure of the temperature at which
your crock-pot operates, use a meat thermometer to test the mixture. It should be
between 176-212°F, or just below boiling. The soap should be completely saponified
in 15-20 minutes. For experienced soap-makers, it is possible to tell when
saponification has completed by tasting the soap (it shouldn’t make your tongue tingle,
or burn), or by determining visually when the soap has reached a gel texture,
characteristic of complete saponification. It is also possible to determine whether
saponification has completed by testing the pH of the soap.
Unlike cold-process soap, hot-process soap can be used immediately after it has
cooled and hardened, because it should be completely neutralized already; therefore,
there is no curing time necessary. However, it is still a good idea to cure the soap,
instead of using it right away, because the soap may still be soft or spongy, and may
not lather properly, or last as long.
WARM-PROCESS (OR OVEN HOT-PROCESS) METHOD
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