I like to make soap once a year, and make enough for at least a year. It’s a very satisfying thing to do; I can make enough for our family for a year or more and only spend about $15 and a little time.
I start by rendering fat from either sheep or cattle, whichever I can easily source. I put it in a roaster in the oven and bake it at about 150°C for several hours. As the tallow melts out of the fat, I ladle it out of a corner, then put it back in the oven. Eventually, I take a pancake turner and cut through the fat to help melt more of it out. When it’s still very hot, it needs to be in a metal bowl, and then when it cools down a bit I put it in a plastic carton and, after it’s cool, put it in the freezer until I’m ready to use it.
To make the soap, I melt 13 cups of fat in a large pot. Then, I measure out 12 ounces of lye (caustic soda) into a dry bowl. Put 4 cups of cold water in a large glass dish. I always take it outside for the next step. Carefully pour the lye into the cold water, and stir with a plastic or stainless spoon (not wooden or aluminum) until the lye is dissolved. Now, check the temperature of the melted fat and the lye. They need to be within 10-20 degrees Fahrenheit (I can’t remember the exact number, but it isn’t too crucial) of each other. Once they are a similar temperature, carefully pour the lye water into the fat and stir. If you use a stick blender or hand mixer for this, you’ll reach the next step more quickly.
What you watch for now is called “tracing.” Tracing is simply being able to see a dribble of soap on top when you lift your spoon or the blender out and let it fall back in. Basically, as far as I can tell, it means the soap is thickening enough that it takes an instant to disappear inside again, if that makes sense. When you see tracing, it’s time to pour the soap into the molds—and with cow or sheep fat, you have to work fast, since it hardens quickly at this point! I use plastic Tupperware containers for molds. I made a double batch this year, and filled three 9”x13” containers.
Now, keep the soap as warm as possible for a couple of days, so the chemical reaction between the lye and the fat will keep going. I wrap the containers up in blankets and put them close to the fire.
Two days later, I cut the soap. At this point, it’s still pretty soft. I used a butter knife to cut it into the size blocks we like, and then lifted them out of the containers. If I had left the soap in them for a week or two, the soap would have likely hardened enough that I could pop the whole slab out, and then cut on a cutting board.
I stack the bars of soap in a cardboard box, with newspaper between the layers. This will hopefully keep it drier in our damp house. We keep it in the warmest, driest place we have. We leave it sit to cure for two months to completely finish the saponification process (the chemical reaction).
This is the way I make soap; there are other methods. Do some research for yourself if you are interested in making soap—you’ll probably come up with a lot of tips I don’t know! If you want to make goat’s milk soap, which I do when I have goat’s milk, use it in place of the water. Just be sure to freeze it first, and then let it thaw just till slushy before adding the lye.