Sodium lactate while not being one of those ingredients that is absolutely necessary to make a good bar of soap is one ingredient that once you start using it, you will agree that not only is the soap easier to manage and cut ,but that it also contributes to extending the life of the soap once it hits the shower.
Sodium lactate is the sodium salt of lactic acid. It is a humectant that is frequently used as a substitute for glycerin in lotions and creams, because not only is it a great humectant like glycerin but it has none of the stickiness associated with it. Sodium lactate is used in cold process as well as hot processed soap making to make a hard bar of soap. The difference between soap made with sodium lactate and those made without it is quite significant, especially at higher percentages. Sodium lactate is a clear liquid with very little odor that is soluble in water. Add it to the water mixture before adding the lye. When added to cold process soaps the curing time remains the same however, the soap becomes harder faster and thus is ready to be cut much sooner. This is of great advantage if one does not have the time to wait for the soap to get hard to unmold. My experience is that soap made with sodium lactate is easier to cut, crumbles less and lasts longer in use because of the hardness imparted by this wonderful additive. Add sodium lactate at amounts of 1-3%.
Below is a recipe for olive oil soap with 2% sodium lactate and no fragrance. This is a nice basic recipe for olive oil soap to which may be added superfatting oils and fragrance/essential oil.
Plain Jane Olive Oil Soap - makes 2 pounds
8 oz. coconut oil
24 oz. olive oil
4.44 oz. lye
0.64 oz. sodium lactate
12 oz. water or other liquid
Follow recipe for basic cold process or hot process soap, adding sodium lactate to water before adding lye.
Sources for Sodium Lactate:
Camden Grey sells everything needed for soap making. Customer service is wonderful and they ship orders out promptly.
The Sage has one of the best lye calculators out there. They have many of the supplies needed to make soaps and lotions and once I have decided to make a certain kind of soap, I always use their lye calculator to make sure my numbers are okay.