In Part 1 we discussed the ingredients, the equipment you’ll need, a few safety rules, and how to calculate how much lye to mix with your fat, depending on the fat’s saponification value. Here we’ll discuss how to combine the ingredients and form the soap.
I have a secret tip for making sure your soap has the aroma you intend. Remember in part 1 we discussed calculating how much lye to use to react with the fats, and then subtracting 5% of that amount to make sure not all the oil reacts. The trick is this: save a bit of your aromatic oil for the last step, after mixing all the other oil and lye. That way any oil remaining unreacted in the mixture will be the oil that has the aroma you like. For instance, if you want it to smell like lavender, add essential oil of lavender last. If you want it to smell like olive oil, add the olive oil last.
See the step by step instructions below.
Mixing the Ingredients for Soap
- Mix the lye and water by pouring the lye into the water, not the water into the lye. See Part 1 for details.
- Melt your fats. If you’re using fats that are liquid at room temperature, like vegetable oil, skip this step. Let the fats cool back down to 100 degrees or so.
- Using a stainless steel, plastic, glass, or enameled cast iron container, combine the lye/water mixture with the fats, but reserve your aromatic oils for the last, after mixing. These oils are whatever you want the soap to smell like, such as olive oil, coconut oil, and/or the essential oil of lemon, for instance. Avoid mixing in aluminum, cast iron, or carbon steel containers.
- Stir by hand or using a mixer until “trace” appears, which is a pearlescent appearance at the surface of the mixture.
- Add the remaining aromatic oil. In this case I added the olive oil and essential oil of lemon at the last. That way whatever oil fails to react with the lye (remember, lye is the limiting reagent) will remain available in its oily state, and it will perfume the soap as desired.
- Pour the soap into a mold. You can use a PVC pipe as shown in the video, or just pour it into a pan. Let it set up for 24 hours.
- Remove the soap from the mold, cut it into bars, and place on a drying rack for a few weeks, then store in a sealed container to stop the drying process and preserve its aroma.