Step 3: Background and Recipe
To make soap out of the bacon fat it's useful to understand a little bit about whats going on. To make soap you need just three ingredients - some kind of pure fat, water, and lye. The lye chemically turns the fat into soap through a process called saponification. Thats when the triglyceride molecules in the fat bond with the sodium hydroxide molecules (lye) and form 1 new soap molecule and a glycerin molecule. You can check out James Hershberger's chemical explanation of saponification to learn more.
Having the right amount of lye is important. Too much lye and you will have extra left over in your soap when the chemical process is complete - this will mean your soap will have lye in it when it's done curing and it could burn your skin. Too little lye and your soap will have some actual fat left in it and instead of cleaning you, it will just grease you up. Most soap makers add too much fat to their soaps on purpose (a process called superfatting) because having a little extra fat in soap actually makes it feel quite nice.
The soap recipe I used was taken from Walton Feed's soap making page. I used a modified version of the basic hand soap recipe that had some small changes made to it based on the information on the useful lye to fat ratio table. I modified the original recipe because I wanted to superfat my soap.
I had 32 ounces of pure lard so I started from there. In order to get a desired excess fat of 5 percent in my finished soap the table called for multiplying the amount of fat I was using by 0.132 in order to figure out how much lye I should use. 32 ounces x 0.132 = 4.224 (roughly 4.2 ounces of lye). Most of the recipes I saw for basic soap used approximately 1/2 water as much water as fat in their recipes. Some call for slightly less water and some call for slightly more. I used 2 cups of water to my 4 cups of fat and it worked out well.
The basic bacon soap recipe is:
4 cups of liquid bacon fat
2 cups cool water
4.2 ounces of lye
3/4 container of bacon bits for exfoliant
15 drops of red food dye for bacon colorings
You can use this basic recipe as is or you can modify it in lots of ways - many of which are covered on Walton Feed's general instructions page. You can superfat your soap to whatever percentage of remaining fat you like, you can add in fragrances and you can add in special kinds of fats like coconut oil and olive oil to make the soap produce more bubbles than it does when using just straight lard (fat from pigs) or tallow (fat from cows).
Since I wanted my bacon soap to be as pure as possible, I just stuck with the basic recipe.