Surfactants (surface-active agents)are compounds that lower the surface tension between two liquids or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants.
They cleanse and build foam by acting at the surface between fat and water. They are able by interacting with water and the fat of the skin, removing the dirt and sebum. Based on their cleansing stenght surfactants are classified into primary and secondary or co-surfactants. Based on the chemical structure there are anionic, amphoteric, non-ionic, and cationic or quaternary agents. Surfactants form the base of all personal cleansing products and can also have wetting, conditioning, defatting, emulsifying, & thickening effects.
Surfactants are also very useful additions for carft made soaps (particularly liquid soaps) where they improve lathering and decrease harshness. They are added to the oil-lye mixture during the boiling procedure. Surfactants greatly accelerate and improve the soap making process.