Saponification in soapmaking is the chemical process in which fats, oils or lipids are converted to soap and glycerin in the presence of an alkaline solution. Saponification literally means “turning into soap” and it gets its name from the Latin word sapo meaning “soap”.
Now let’s break it down and make it simpler for you to understand. Triglyceride molecules are the building blocks of fats, oils and lipids. 3 fatty acids and a glycerol molecule make up a triglyceride. Refer the picture below for more clarity.
During saponification, an alkaline solution (lye solution) reacts with these triglyceride molecules in a double displacement reaction to form soap and glycerin. In soapmaking, we use sodium hydroxide (NaOH) for solid soaps or Potassium Hydroxide (KOH) for liquid soaps. Chemically, soap is a sodium or potassium salt of fatty acid. I tried to illustrate this for you below.
The process of forming soap is a chemically exothermic reaction (heat producing). The entire reaction takes 24-48 hours to complete in cold process soapmaking. Additional heat can speed up & complete the reaction in less than 30 mins like in hot process soapmaking.
Saponification Value
Saponification value (SAP value) or number denotes the number of milligrams of lye required to saponify 1g of fat or oil. This value differs for every oil. And SAP value for sodium hydroxide and potassium hydroxide will also be different. This is exactly the reason why accurate measurements are necessary while weighing ingredients for soapmaking. We are working with chemicals and an incorrect measurement can throw a recipe out of balance and can make it unsafe to use.
Lye Calculators
As you might have already figured, soapmaking involves quite a bit of math & science. Lye calculators save you the trouble of making calculations by hand and avoiding manual errors. Soap Calc is a very common lye calculator among soapmakers.
Have I simplified the saponification process enough for you? Let me know if you have any additional questions in the comments below! Always happy to help!