How does the cold method of soapmaking work?

The cold method of soapmaking is a straightforward process that relies on the chemical reaction known as saponification, where an alkali solution—typically sodium hydroxide—reacts with fats or oils to produce soap and glycerin.123

The process works as follows:

• Mixing: A mixture of fats and oils, often including coconut or palm-kernel oil, is combined with an alkali solution.2
• Proportions: Slightly less alkali is used than the amount theoretically required for complete reaction. This ensures a small amount of unsaponified fat or oil remains in the final product as a superfatting agent, which is beneficial for the skin.2
• Agitation: The mass is stirred and agitated in an open pan until it begins to thicken.2
• Solidification: Once thickened, the mixture is poured into frames. It is left in these frames to complete the saponification process and solidify into soap.42

Because this method is technically simple and requires minimal machinery, it is particularly well-suited for small-scale production.2