In our articles so far we’ve talked about natural ingredients, superfat, hot and cold process soap, about the chemistry of how soap works and about where soap comes from and some interesting information about its history. Let’s go back to chemistry now for a quick word on lye.
To put it shortly, there is no soap without lye and no (properly made) soap with lye. Now, what do I mean by that?
Well, lye or sodium hydroxide is the only chemical product you really need in order to make soap. Otherwise you can have an all-natural ingredient list, no problem. And by the way, you can say natural soap if you’re using all natural ingredients (minus the lye, of course), although soap is really a chemical product itself, since it doesn’t occur by itself anywhere in nature and is the result of a chemical process. Each fat has its own saponification value and the quantity of lye to be added to the fats in order to turn them into soap is calculated on the basis of the individual saponification value of each fat.
The magic of the chemical process of turning fats into soap by using lye means that your whole mixture (water + sodium hydroxide + fats) becomes soap. So there is no lye left in there at the end. And no fat either, unless it’s a superfatted soap (see our article on superfat).
In other words, it’s the same as with baking: we need fire to turn a mixture of flour and water into bread, but once the bread is baked, there is no fire in the bread itself. And no raw dough either. Same story with soap: we use lye to turn a mixture of fats into soap, but at the end there is no lye in the soap itself.