What is the difference between cold and hot soap making process?

Handcrafted soaps made from scratch require three ingredients to become soap: oil (animal or vegetable oil, not petroleum-based oil), water and lye. These three ingredients, when mixed together in correct proportions, combine and chemically change into soap - a process called "saponification". They may include other ingredients to provide additional benefits or to colour or scent the soap, but these are not part of the chemical process. Handcrafted soap from scratch can be made either through hot or cold processing.

Cold Process Soap.

The term "cold process" refers to the fact that no heat is applied during soapmaking. The lye solution and oils at the needed temperature are combined and mixed. As mixing continues, the mixture will gradually thicken and get warmer. This is the chemical reaction of the oils and lye becoming soap. Once this consistency is reached, any other ingredients (herbs, clays, scent, colour etc) are added to the soap. At that point, the soap is ready to be poured into molds. By not using additional temperature this method gives time to decorate the soaps. Then, when the soap is cooled and hardened it can be cut. The final stage is curing the soap for 3 - 8 weeks.

Hot Process Soap

"Hot process" soap refers to the fact that an outside source of heat is applied to make the soap. With hot processed soap, the lye solution and oils are mixed together and then an outside source of heat is used - the added heat causes the saponification process. Once the soap is fully saponified (it takes 3-6 hours for handcrafted soap) it can be poured into molds and once it has cooled and hardened it can be cut. High temperature turns the soap into a "melted" form and does not give time for decoration.

Hot process is historical as our ancestors used this method by making soap using fat, ash (modern lye), water and temperature.





fat (vegetable or animal), water, lye

fat (vegetable or animal), water, lye










ready to use

in 4-6 weeks

when is harden up


Once the soaps bars, either made by cold or hot process, are completely cured and hardened they can be packaged and used!

What fat: vegetable or animal, what process: cold or hot it depends on soap maker preferences.

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