Saponification is most significantly known as the process of making soap. Saponification occurs when a base such as sodium hydroxide reacts with a triglyceride such as animal fat. The result is glycerin and soap.
It is also used to make kitchen fire extinguishers and is involved in art as well. Grease fires are common in the kitchen. Class K fire extinguishers contain substances to cover and saponify the oil. Once it is turned into soap, the oil cannot burn.
Older oil paintings have saponification occurring between the oils in the paint and the bases in the pigments. A type of soap forms that obstructs the art.