What is Sodium Hydroxide?
You can't make soap without lye. Solid soap requires a sodium hydroxide solution and liquid soap requires a potassium hydroxide solution. You could make soap using the ancient Wood Ash Method, which dates back thousands of years, but you would still be using lye (extracted from wood ash).
Sodium hydroxide (NaOH), a.k.a. lye, is a crucial ingredient in making cold process soap. This highly alkaline compound, with a pH of around 13, triggers the saponification process. Saponification is where oils/fats combined with a lye solution (sodium hydroxide and liquid) transform into a solid bar of soap and glycerin. Although raw sodium hydroxide is highly reactive (requiring safety equipment to handle it), it becomes neutralized during the soapmaking process - and creates a safe, solid bar of soap.
For every batch of cold process soap we make, I perform a residual alkalinity test. This test ensures that the bars are alkaline neutral and ready to be used. I also include all of the ingredients on the label. I believe in full transparency, and that is why sodium hydroxide is on the label alongside the other ingredients.