What products result when natural fats react with caustic soda during soapmaking?

When natural fats or oils react with caustic soda (sodium hydroxide) during the process of soapmaking, the chemical reaction—known as saponification—produces two primary substances:

• Sodium fatty acid salt: This is the soap itself.1
• Glycerin (or glycerol): A clear, viscous liquid that serves as a by-product of the reaction.12

This reaction is the fundamental basis for traditional soapmaking. While modern industrial processes often use fatty acids directly to produce soap and water, the traditional method using natural fats consistently yields soap and glycerin.13