What is Saponification?

The manufacturing of soap traces back thousands of years. Archeologists have discovered records of soap making inscribed on clay tablets in Mesopotamia from 3000 BC. There is also evidence of soap use by both the early Roman and Egyptian cultures. By the 1600s in Europe, with the findings of Louis Pasteur, there was a strong movement toward good hygiene. Doctors began prescribing the use of soap. Today more than ever, we know the importance of proper washing with soap. 

No matter how soap is made, whether in a large kettle with heat, or using the cold-process method, all soaps share a few common traits. Soap is a salt, created through a chemical reaction that occurs when a fatty acid and a base are combined. This reaction is called Saponification.

To help explain Saponification in its simplest form, here are the basics of how soap is made. 

Saponification is a process that converts fats, oils, or lipids (the acid) into soap by combining them with Sodium Hydroxide, Lye (the base). The chemical reaction relies on friction and self-generated heat. Through saponification, the acid and the base are neutralized.

A simple soap batch is made by measuring a oil (an Acid) in a non-reactive vessel and in a plastic container Sodium Hydroxide, Lye, (a Base) is dissolved in a liquid. (Milk or Water) This "Lye Liquid" is carefully combined with the oils in the non-reactive vessel.   

Knowing the proportions of acid to base needed for saponification is the key. This is determined by knowing the SAP value of each oil (acid) in the batch. The SAP value is the amount (g) of sodium hydroxide needed to completely saponify a particular oil. Each type of oil, whether vegetable or animal, has a different SAP value based on its molecular structure.

Once the proper amount of acid and base are combined, the chemical reaction begins. As the mixture is agitated, the oils go from translucent to opaque. When "trace" occurs, the cold-processed soap has reached a point in saponification where it is ready for the optional incorporation of additives.

Saponification is now well underway and the soap can be poured into molds. The molds are placed in a draft-free environment and left to sit for a period of time to facilitate the continuing saponification. The molds will continue to generate heat from the chemical reaction for a period of hours. Once cooled, the soap will be ready to unmold and if necessary, cut. Saponification is virtually complete at this point. The soap is left to cure and harden for a period of time before it is ready for use, 3 to 4 weeks minimum.

It seems very likely. that the earliest form of soap was accidentally created.  An ancient legend says there was temple in Rome on  Mount Sapo, a mythical mountain supposed to exist somewhere near Rome, on a hillside above a river and a strange foaming substance was found seeping into the river below the temple. The rendered fats (acid) from roasted animal sacrifices would combine with the ash (base) from the fire. This mixture was washed by the rain down the hillside and into the river where women noticed how clean their clothes became when washed in this foamy substance.  

Luckily, it's 2024, and all the math behind the chemistry is taken care of, because, there's an App for that!.  

JD