Hot process soap making is one of most gratifying types of soap making because the results are immediate. When soap is made in this way, the fragrance tends to be more pronounced owing to the fact that the lye is cooked out before fragrances or additives are added so the lye does destroy or morph the fragrance.
One of the challenges with making soap this way, though is that after the soap is cooked, you have only minutes once it reaches a manageable temperature and a temperature below the flashpoint of the fragrance or essential oils used, to manipulate it into the mold and finish it off with whatever embellishments you choose.
The first step to making consistent batches of hot process soaps is to get a good basic recipe that works and vary this recipe with additives and luxurious oils or butters.
Here is a basic recipe that gives amounts for 2 pound, 3 pound and 4 pound batches. This recipe calls for a coconut/olive oil/butter blend that is both mild and very sudsy owing to its base of olive oil and coconut oil. Olive oil produces a bar that is low in bubbles yet very mild on the skin, while coconut oil produces a bar that has lots of bubbles, but maybe drying to the skin. Pairing these two together, one gets the best of both worlds – lots of suds and mildness.
Next to having a great recipe for consistent batches of soap, is having a lye calculator that calculates lye and fat ratios that ensures that excess fat, rather than lye is leftover in the soap after saponification. One of the best lye calculators on the web is the lye calculator from Majestic Sage.
With this calculator, I have formulated a soap that is 50% coconut oil and 50% olive oil with the addition of 2% shea butter super fatting to make this bar more luxurious and moisturizing. Die hard purist suggest that no more than 20-25% coconut oil should be used in soaps because the coconut oil, though lending large fluffy bubbles to the soap, tends to be drying. Thus, to counter that, I have added shea butter (or any other kind of nut butter or luxury oils may be used) at 2%.
Finished batch size: 2 pounds
16oz. coconut oil
16oz. olive oil
12oz.water (6oz. liquid per pound of fats)
4.80oz. lye (allows a buffer of 6% fat to be in soap)
0.64oz. shea butter(to superfat)
Finished batch size: 3 pounds
24oz. coconut oil
24oz. olive oil
0.96oz. shea butter(to superfat)
Finished batch size: 4 pounds
32oz. coconut oil
32oz. olive oil
1.28oz. shea butter(to superfat)
Follow instructions and precautions for making cold process soap. After lye and oil are cool, say to no higher than 100 degrees Fahrenheit, combine lye water and melted oils in a large pot with about 4-6 inches head room and stir. At this point, you may stir until soap traces, but this is optional. Soap does not have to come to trace. Instead, stir mixture with a wire whisk until opaque and place in a 225 degree preheated oven. Set timer for 60 minutes. After twenty minutes, take mixture out of the oven and stir with wire whisk. Mixture may not appear any different from when it was first put in the oven, except for a pool of clear liquid floating on the surface. Stir and place back in the oven and check again in twenty minutes.
What we are looking for is for the mixture to change and become translucent somewhat like applesauce. This may take a further twenty minutes or so. At the end of the 60 minutes, check mixture. If it is not looking like applesauce, place back in the oven and let it sit for another twenty minutes. At this stage it should have passed the applesauce stage and should look like curdled applesauce. Wisk vigorously and test for lye. Depending on various factors, including oven temperature and the oils used, some mixtures take longer to cook than others. At the end of the cook, which may last anywhere from 6o minutes to 90 minutes, all the lye should have cooked out. The only discernable liquids in the pot should be soap, which appears as separated applesauce and some liquid, which may be a mixture of water and excess fat. Use a whisk to whisk these into one homogenous mass.
I usually take a small piece of soap and soap my hands with it under running water. If it stings, then there is some lye in it. If that happens, put pot back in the oven and set timer for another 20 minutes, then test again. Lye should be completely cooked out of soap. Aternatively, litmus paper may be used to test for lye. Run soap under water and create a generous lather. Run PH paper through this. A good PH for soap is anything under ten. After taking soap out of the oven, it may appear that soap has some liquid at the bottom of the pot. This is excess water and oil. Use a whisk and stir the soap until smooth.
Fragrances and essential oils may be added at this stage. First check flashpoint of fragrance/essential oil and add to soap after it has cooled ten or twenty degrees below that flashpoint temperature. Try to handle soap as little as possible and work as fast as you can. The soap will be difficult to manipulate. Combine super fat oils or melted butter with fragrance/essential oil and stir vigorously into mixture. Pour soap into plastic lined mold. The soap will be thick and not easy to manipulate into mold. Shake the mold to get soap to level into the mold and fold back excess plastic to smooth out the top of soap. If decorating top of soap, spritz with water and sprinkle on herbs, seeds, etc. Leave in a secure place to cool and set. I usually leave my soap in the mold to cool and set for about 4-6 hours. At the end of which soap is ready to be turned out and cut into bars.
Magestic Sage Lye Calculator - Good Lye Calculator
Majestic Sage PH test strips - PH Testing Strips