In Colonial times, soap was made by boiling lye, slowly dissolving animal fat in it and then cooking the ingredients for long hours. Soap requires both a fatty acid and an alkali, which is a chemical that neutralizes acids. The fatty acid is the animal fat, and the alkali is lye or potash.
According to Augustana College, lye, one of the components of soap, was made by mixing water and wood ash together in a container with holes. The lye was the drippings from this combination.
By the 1800s, innovations in soap making made it possible to obtain the alkali without using lye. The new process, named the Leblanc process after its inventor Nicholas Leblanc, formed the alkali soda by using salt, sulfuric acid, limestone and coal. Another process invented by Augustin Jean Fresenel formed soda by using salt and ammonia, which had the added benefit of no toxic side effects, in contrast to the Leblanc process.
Soap making has been around since approximately 3000 B.C. as directions inscribed on a Sumerian clay tablet from roughly the same era have been found; however, the ancient Romans really got into the production of soap. In fact, a soap factory was unearthed in Pompeii.