Tuesday, August 18, 2009
Public Service Announcement: ALL True Bar Soap is Made with Sodium Hydroxide AKA Lye
Soap is created through a chemical reaction called saponification. Saponifiable substances are those that can be converted into soap. Sodium hydroxide or "lye" (NaOH) is a caustic (alkali) base. During saponification the alkali base such reacts with a fatty acid side chain of an ester molecule from a fat or oil. Oils and fats are fatty esters in the form of triglycerides. When Sodium Hydroxide is used a hard soap is formed. The alkali (OH group) breaks the ester bond and releases the fatty acid salt and glycerol. The fatty acid salt has a hydrophobic (water fearing) and a hydrophilic (water loving) end. In this way the molecule (soap) can mix with oils or water to act as emulsifiers thereby mixing with water and oils to clean. Many people ask if soap can be made with out lye OR claim that true soap can be made without lye. The answer is no, true soap cannot be made without using lye.
Modern cold process soap making yields a glycerin-rich soap. This kind of soap was once called 'lye soap'. Many people think of lye soap is unpleasant and harsh to use. This is because in the past people made soap with too much lye, and it remained in the bar of soap irritating the skin. Without the scientific data and scales available today, the soap makers of the past approximated the amount of lye to add to the fats. If not enough lye was added, the mixture was soft and not usable. If too much lye was added, some extra lye would remain in the soap but the soap could be used. Therefore, the preference was to add extra lye to ensure the soap would be usable. Using modern calculations and methods, when made correctly, no lye remains in the bar of soap.
All bar soaps and shampoo bars are made at AquarianBath are made with Sodium Hydroxide.