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Hot Process Soap
COURTESY OF: Lynn Watts, BayFrame House Herbal Soaps

I make my soap using a hot-process method, an adapted method I use, and I've never had a batch separate or fail. I got the information for hot process or 'cooking soap' from a web site for old-timey methods of doing things.

These instructions assume you already know how to handle lye and calculate the amount of lye to use for your recipe. You can use your usual recipe and just finish the soap by using this method.

EQUIPMENT: Tall enamel pan or other narrow, tall soaping pot (not aluminum) Candlemaking thermometer or other thermometer to 400 degree F. range Tall plastic spoon rated to temperature above 330 degrees F. Large rectangular plastic container with lid Wax paper or non-melting plastic wrap Long bladed non-serrated knife

MAKING SOAP: I use an enamel pan (very tall) and put the fat into it and melt it, then turn off the heat. Then I mix the water/lye in a plastic container and let both cool to between 90-100 degrees. If the oil is already liquid (like olive oil) I heat it to about 90 degrees and mix the water/lye with it. I add the lye/water to the fat in the enamel pan slowly, stirring briskly. I follow whatever the recipe says about how long to achieve a trace.

COOKING THE SOAP: After it traces, I turn on the heat and slowly raise the temperature (using a candlemaking thermometer that goes up to 400 degrees) to between 250F and 330F degrees, stirring the whole time. I turn on the overhead fan to disperse the heat. The temperature range depends on the type of oil used. Olive oil wants to go all the way to 330F, while coconut/palm/olive oil blends don't need to go so high, somewhere between 250-270F. I keep it in my enamel pot to "cook" the water out of the soap and accelerate the saponification process. I stir pretty continuously, and leave a the thermometer in the mixture to monitor how it's doing.

A water-based mixture will not go above 220 degrees (that's why double-boilers won't burn things), but as the water evaporates, the fats that are left get hotter. The oil will actually boil. At some point little soapettes will start forming, so I know I'm getting close. Looks like grits on the spoon. Before it hits the wall and becomes too thick, I put the pot in a sink full of cold water to cool down. When you see the bubbles starting to come up through the soap at about the same place all the time (like making custard), it's time to stop. The water evaporates, the lye/water and fat traces and saponifies, and within an hour or so I have some VERY HOT soap. It's like cooking a recipe for food, you can "tell" when it's ready. As long as it's gotten above 220 degrees you've gotten past the boiling point of water and the water will have become steam and be gone. Different oils react differently - olive oil likes a higher temperature than coconut/palm, for instance.

SAFETY: Remember, though, to be CAREFUL. At first you're working with a caustic mixture that you're raising to a high temperature. By the time it reaches 250 degrees, it's usually not caustic any more, but it is VERY HOT!!! Don't let it bubble up on you, or spill it on yourself while it's still very hot. I have accidentally spilled the cooled-down mixture on myself while filling the molds, and it does not have lye in it any more, it cools down to just pure white soap. But even without the active lye, at over 220F it is hot enough to burn you if you are careless. BE CAREFUL and don't burn yourself.

BLENDER METHOD: I tried an experiment once and ladled some out into the blender at 220 degrees and it traced and made soap immediately. Poured that batch directly into my small molds, let sit 24 hours and unmolded. It was wonderful.

COOLING THE SOAP: I keep stirring while the soap cools back down. To speed up the cooling process, you should put the pot into a sink nearly full of cold water (doesn't have to be ice water). Otherwise, it will keep cooking from its own internal heat. As it cools, it will thicken up and make an almost-finished basic soap before it goes into the mold. Even with olive oil as the fat, I've never had a problem getting it to thicken up.

FINISHING THE SOAP: The cooked method removes the extra water. When it's cooled down to around 100F, I add any essential oils or fragrance oils and pour into a giant rectangular Rubbermaid container. I squish it down (with gloves, just in case) to remove any air bubbles or gaps, and after I put plastic wrap or wax paper right on top of the soap I squish it down some more. Leave it for 24 hours, then score rectangles with a knife. Next day or two I dump it out, break apart on the score lines, and there it is. FINISHED BASIC SOAP.

CURING THE SOAP: I've never had separation, lye pockets, curdling or other problems. I've also never had soda ash on my soap. I don't wrap the soap to keep it warm, I just stick it under the sink. I have "hot processed" with just veggie oil (olive, palm, coconut, safflower, canola, sunflower), olive oil and lard, and just lard using this method, and all the soap came out very white and hard. After unmolding and cutting, it needs to cure for 2-3 weeks to get hard and finish firming before using it. But if you get impatient to try it, you can try it a little earlier to test the lathering and scent. I almost always do!

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