01 / The starting oils
Soapmaking begins with fats or oils. Their different fatty acid profiles influence the cleansing character, feel, foam and other properties of the finished soap.
02 / The role of potassium hydroxide
Potassium hydroxide (KOH) is the strong alkali used in many liquid soap formulations. Its purpose is to react with triglycerides and fatty acids to form potassium salts of fatty acids—the actual soap molecules. It is a manufacturing reactant, not a featured skin-care benefit.
In simplified terms: triglycerides + potassium hydroxide → potassium salts of fatty acids (soap) + glycerol.
03 / Saponification
Under controlled conditions, the alkali reacts with the starting oils. The rate and completeness depend on formulation and process conditions. Finished soap should be checked for appropriate quality, including absence of excess caustic alkali.
04 / Dilution and finishing
Traditional liquid soap is commonly diluted with water and may be finished or adjusted depending on the formulation. A finished soap is not simply a mixture of the original oils and water: saponification creates new molecules.
05 / What about glycerin?
Glycerol, also called glycerin, is produced as part of saponification. How much remains in the finished product depends on the manufacturing and finishing process.
Why do we call it true soap?
Traditional soap derives its main cleaning action from fatty acid salts made through saponification. Many modern liquid cleansers instead use non-soap surfactants. Both categories can clean effectively; their pH and compatibility with individual skin vary.
Compare cleanser types ↗