Soap making is an ancient art form dating back to Babylon circa 2800 BC. How they discovered it, my research has yet uncover, but we do know it’s been around for centuries. Back then they didn’t have calculators, scales, or food-grade, lab-created chemicals. They just threw in some sort of alkali into some sort of oil and hoped for the best. Some of you might even remember your grandmother making soap, what did that look like? Do you remember the end product being kinda harsh? Why is soap now so different from soap made just a few decades ago?
To know soap we must know chemistry. Chemistry is far younger than soap making, and before we call it “chemistry” we must call it “alchemy”. Alchemy is not what modern people would call “scientific.” It is the study of nature, metallurgy, magic, and the occult. But before even alchemy, there was Greece and Aristotle. There was atomism. Atomism is probably the first notion that the natural world was based on two things: atoms and a void wherein atoms are set to collide. And still these ideas were a few thousand years after the first documented soap!
Real chemistry didn’t even begin until Gerber introduced the concept back in the 9th century, a far cry from our early Babylonian soaps. So, you may ask, what’s the big deal? If they were able to make soap before science, what’s so special about making it now? Well, it’s a whole lot safer, for one. It’s also customizable to different needs. You want a bar for psoriasis? You want one for sensitive skin or something highly moisturizing? How about something utilitarian that’s also aesthetically pleasing to look at? It can be done! We now have calculators that allow us to precisely mix ingredients to obtain an expected outcome.
Allow me to explain how it works. Saponification is the process of turning a fatty acid (oil or butter) into a salt. We all know that oils and butters (including those of vegetable and animal origins) are made up of triglycerides, or fatty acids. When combined with an alkaline solution (we use either sodium hydroxide, NaOH, or potassium hydroxide, KOH, dispersed in water) it brings about the chemical reaction known as saponification. Not only does this reaction create the soap we all know and love, but it also creates the byproduct glycerin, a skin-softening humectant.
So what’s the big deal? Just mix some oils and lye together. Boom! Soap.
Hold your horses. Every single oil or butter has a unique point at which is will achieve saponification. Just as no oil contains exactly the same set of triglycerides, lye reacts with each of them at different rates. Since we always use more than one oil at a time in our recipes we must calculate both the saponification value of the oil as well as the percentage used in each batch.
So, then what happens to all of that water that was mixed with the lye?
During saponification the chemical process of the triglycerides combining with the lye causes an exothermic reaction. This can cause the soap to heat to over 130 degrees for a short period of time and if you use the hot process method, even hotter. This heat and long cure time gives the soap an opportunity to evaporate its excess water creating a harder, more gentle, and longer lasting bar of soap.
This is just a taste of some of the chemistry involved in soap making. In the future we can consider the components that affect shelf life, as well as the art of fragrances and color swirling.
Don’t forget to wash behind your ears,