Saponification in the Soap Making Process

Blending Soap
Blending Soap. Cohen / EyeEm Creative #: 674736697 Getty

Definition: Saponification is the primary chemical reaction of soap making.

It is an exothermic (gives off heat) chemical reaction that occurs when fats or oils (fatty acids) come into contact with lye (a base). Saponification literally means "turning into soap" from the root word, "sapo", which is Latin for soap. The by-products of the saponification reaction, in which the acid and the base combine, are glycerin and soap.

Oils + lye (dispersed into water) = soap + glycerin

Oils and fats each have what is called a “saponification value”, which is the amount of lye needed to completely neutralize them into the soap with no lye left over. Each oil has a different value, which is why it’s important to always run soap recipes through a lye calculator. The calculator will help ensure that the ratios of water, oils, and lye are correct and will produce the results you are looking for.

There are many variables that will impact saponification and different soap ingredients have very distinct characteristics. Be sure to research the types of acids you are using (ex: coconut oil, olive oil, etc.) and the results they may have on the final soap product. Depending on the ingredients used, soaps can vary greatly with different attributes such as lather, bar consistency and cleansing ability.

Most of the ingredients for soap making can be found in a grocery or hardware store.

Be sure to buy pure high-quality lye that is made specifically for soap making. In addition to the basic soap ingredients, there are many options that can be added to the soap to alter the fragrance, consistency, and color of the soap. Once the basic soap making has proven successful, try experimenting with other soap variations.

The saponification generally takes about 24-48 hours to complete once the lye and oils have been mixed and the raw soap has been poured into the mold. This process can be sped up by adding more heat or slowed down by keeping the process very cool.