Saponification is the name of the chemical reaction that produces soap. In the process, animal or vegetable fat is converted into soap (a fatty acid) and alcohol. The reaction requires a solution of an alkali (e.g., sodium hydroxide or potassium hydroxide) in water and also heat.

Why does saponification require heat?

Saponification is an exothermic chemical reaction—which means that it gives off heat—that occurs when fats or oils (fatty acids) come into contact with lye, a base. ... This process can be sped up by adding more heat or slowed down by keeping the process cold.

How does heat affect saponification?

If the lye solution is too cold, it can solidify the oils and butters upon contact. If the lye is extremely hot, it can cause the saponification process to speed up dramatically. This is problematic if the soap design involves lots of layers, swirls or other complex techniques.