Monday, April 8, 2013
So... how do you make soap, anyway?
In general terms, then, soap is made through a process called saponification. There are two parts to the soap mixture, and when those two parts are combined, they saponify, and the chemical reaction forms soap.
The first half is a mixture of lye (which is extremely caustic and can cause chemical burns, which is why I look like a mad scientist when I make soap, with a face mask and safety goggles and gloves) and liquid- usually water, but depending on the soap, you can also use milk, coconut milk, beer, et cetera. The second half consists of oils. You can use pretty much any oil you can think of to make soap, but since each oil has different properties, the better the oils, the better the soap. Also, you might have
different purposes for different kinds of soap, so you'd want to choose the right oils to make, say, a mild moisturizing soap, or a soap with a very bubbly lather, or a super-cleansing utility-style bar, or any number of other qualities. Some people use animal fats like lard or tallow, which I understand make some wonderful soap, but I never use any animal fats, only vegetarian oils like coconut, olive, castor, avocado, almond, wheat germ, et cetera. I love to work with honey and beeswax, so I mix those in at this stage too. If you use beeswax, it's very important to know your source, because many hives are managed with chemicals, and wax absorbs everything it comes into contact with. So if bees are managed with chemicals it goes right into the wax and then onto you, when you use your soap. (Our bees, obviously, are chemical-free, or I wouldn't be off on a tangent about it.)
The two halves have to be measured extremely carefully, so that they neutralize each other evenly. If your mixture has too much lye in it, the soap will remain caustic and not be safe to use. If you have too many oils, the extra oil in the soap will go rancid. Each kind of oil saponifies at a different rate, so you have to be certain that each one is measured down to the gram, and that you're using the exact right amount of lye for that combination. And the two halves have to be mixed at just the right temperature or they can curdle, separate or refuse to "trace." When you combine into one mixture, you then have to stir it until it reaches trace, the stage at which, if you trail some of the mixture across the surface, it leaves a trail, or trace, before sinking back into the mixture. Depending on the soap and how you stir it, this can take an hour or more. But you can't stir too long, either, because if it reaches trace and you keep going, the mixture can quickly seize and become completely solid right in the pot. You have to watch carefully, because some soap can reach trace in less than a minute.
Then the fun part: additives. These can turn your soap from super-plain and dull to amazing. Fragrances, colors, essential oils, vitamin E, exfoliants, botanicals... a creative person can come up with infinite variations. You mix these in as you're bringing the soap to trace (not after, because if your soap is getting ready to seize you won't want to take the time to mix in anything extra; you have to move quickly). And some of the additives (especially essential oils) can accelerate trace, making it happen very fast. This is also the time when, if you're making soap with swirls or layers of different colors, you'd split the batch into separate containers and mix in different additives.
Then you pour your soap into molds, cover it, and (again depending on what you're trying to do with the soap) insulate it or chill it. After a day, you can unmold it and slice it, and wait for it to "cure." Curing is sort of like ripening for soap. It takes time for the saponification process to be complete, and until then, the soap remains caustic and isn't safe to use on skin. The length of time varies from recipe to recipe, but three weeks is usually a good cure time. That time also allows the soap to harden (it's soft when it's newly-made), and the harder a bar of soap is, the longer-lasting it is. Finally you can trim your cured soap, smoothing edges and any imperfections, and package it up.
And that's how soap is made! There are, of course, tons and tons of websites and books on the subject, and variations in almost every step, but those are the basics.