Join us as we perform a HTHP castile soap experiment. The Ultimate Guide to Hot Process Soap teaches students how to formulate informed High Temperature Hot Process (HTHP) recipes based on saponification and fatty acid soap science and the knowledge and use of physics. Although HTHP recipes are best made with what teach as "informed recipes", the process can still be used to make recipes low in unsaturated fats, although not as quickly or efficiently. When we add these components to other factors that accelerate the saponification reaction rate like increased chemical surface area and mixing and increased heat energy from the HTHP method, in addition to a reduction in water and reaction accelerants, we are quickly able to increase the rate of reaction and create a hot process soap in just a few short minutes.

Today we will perform an experiment that creates a fully saponified castile soap made from 100% olive oil using the HTHP method. The recipe will be made with a 28% water concentration and will be made without a crockpot, although you may use one if you prefer. In addition to olive oil, lye, and water, we will add clove oil which contains eugenol, an alcohol that has an acidic proton that acts as a reaction accelerant. We can add eugenol to recipes that are high in unsaturated fats and it will immediately react with the sodium hydroxide and increase the overall reaction rate. Because of the small amount used and the immediate reaction, there is no change in fragrance or risk of irritation.


This experiment makes plain ole fashion castile soap, but please feel free to customize it however you would like. If you want a more fluid recipe, you can cook with a water discount and then add the moisture back to the recipe after the saponification process or use a higher water concentration at the beginning. You can add milk, yogurt, sugar, fragrances or any other additives that you wish to use.

Recipe:
32oz olive oil (6% cook superfat)
8.96 ounces water (This is a 28% water concentration and is very high discount for hot process soap. It will result in a very thick soap at a faster rate. For a more hydrated soap, use 32% or 10.24oz or the full 38% at 12.16oz)
4.07 ounces NaOH
Few drops of clove (1.52.5ppt for an exact measurement, for this play batch, I just sprinkle a few drops)
You can also use finished castile soap or add stearic acid for a trace accelerant if you don’t have clove oil (be sure to calculate stearic acid in soap calculator)

Directions: Use the knowledge and directions from The Ultimate Guide to Hot Process Soap for the HTHP method (continuous immersion blender high temperature hot process)
1. Because the recipe as a decreased rate of reaction, you can use a higher starting temperature. I heat my oils to 230250F (do not exceed 250F).
2. Complete the HTHP continuous mixing process until the soap has finished with any volume expansions due to the chemical reaction and heat, then cover with plastic wrap. Do you have a weak immersion blender? Use the 22 method instead of continuous mixing. Mix for 2 minutes, cover and rest for 2 minutes. And repeat until finished.
3. Stir every few minutes until the pH has reached soapneutral. This is the perfect time to do your dishes and clean your area!.
To test, make a soap solution with 1g soap in 100g water. If you are an experienced hot process soap maker, this is not necessary; however, if you would like to test the pH of this particular soap, please be aware that the soap is very hot and it is not advisable to test using the zaptest or by holding, unless cooled, thus, my use of a cup is necessary for this example.
4. Mold your recipe (you may refrigerate or freeze if desired)
5. Cut your Castile soap AS SOON AS IT IS HARD ENOUGH! Because this soap has a low water concentration and because it is created using HTHP, it will be incredibly hard. I recommend checking after an hour. Enjoy a small sample of your castile hot process soap and cure the rest for added hardness, increased lather stability and a longer lasting, gently cleansing soap!

Video: I left the camera on the entire time when shooting this so that you could see exactly how the process works and how long to let it sit, in addition to checking the temperature and the pH of the soap. Please disregard all of the extra noises.

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The Ultimate Guide to Hot Process Soap Soap Science, Recipe Formulation, Low Temperature Hot Process and High Temperature Fluid Hot Process. With over 400 pages, our book has everything you need to know from start to finish about hot process soap making, including how to make stunning fluid hot process.

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