Saponification

This word (quite a mouthful) is used to describe the chemical interaction which takes place when the lye, distilled-water and fats/oils mix together to create soap. The Latin word for soap, “sopa” is it’s possible origin.

As new starters, we can simply follow a recipe from a trusted source. Their creators have usually already done all of the calculations, according to the ingredients. Providing that we carefully weigh those ingredients to ensure that we are complying with the recipe, it is usually plain sailing and eventually, rather routine. The real fun begins with exploration, invention and innovation. This is where we choose what type of soap we want to make along with the ingredients to provide the qualities we expect of it. This also requires us to do calculations involving, ratios, percentages, weights and strengths (densities) including the previously mentioned Sap values.

In the early days of soap making, there would have been no measuring. The fats from the slaughtered animals would have simply been mixed with water and wood ash from the fire pits and then left to cure. To avoid being left with a smelly slop of yuk, the early soapers would probably have overloaded the mixture with wood ash (lye) to make sure it cured as a usable hard lump. The excess of lye would not have been a problem because the coarse soap would have been used to clean the animal hides rather than human skin. I suspect that human survival had the edge on personal hygiene, and also our ancestors probably had skin as tough as rhino hide.

Nowadays, modern science has given us the ability to determine exactly the weight of how much lye is required to “saponify” a one gram amount of a particular oil/fat. This figure is known as its “Sap value.”