Sodium hydroxide, more commonly known as lye, is a key ingredient in soapmaking. The reaction between sodium hydroxide and the fats, or oils, in the soap raises the temperature and causes the oils and milk to saponify. Saponification is the process by which the oils harden and a lather is created. Before sale we test each batch with pH strips. We also use the soap ourselves to ensure our soaps are of the highest quality.