there has been quite a bit of traffic about this on other fora lately. I'm not sure what the rules are for linking to them, so I'll summarize.
making very good shave soap at home is EASY.
a smart guy reverse engineered Martin de Candre, and modified the formula to make it a little easier to make at home.
the ingredients are stearic acid, coconut oil, water and potassium hydroxide. I used stearic 55%, coconut 45%.
it works better than any other shave soap I have tried previously.
use
soapcalc to get the quantities right- and measure as accurately as you can.
a word of caution- potassium hydroxide is lye. it will burn you if it gets on your skin. (more accurately, it will try to convert all of the oils in your skin into soap. there isn't enough oil in your skin, so it attacks the rest of your skin...) when it is mixed with water it reacts, and the fumes are dangerous to breathe (trying to make your lungs into soap...). add the lye to the water, and slowly. if you add the water to the lye, it will react rapidly and violently, and probably splash out and get on you (see the bit about lye and skin).
make it hot process using a crockpot. do not use metal containers or implements for this process. put the stearic and coconut into the crockpot and melt them together. I got impatient and melted them in the microwave first. put the water in a heat resistant container- I used a coffeemaker carafe from the thrift store. add the potassium hydroxide slowly, letting it react and dissolve into the water. do this outdoors. add that mix to the oils, mixing vigorously. let it cook for a couple of hours, then scoop it out into a mug or bowl or mold or whatever you want. MdC uses a jar, although sometimes they do a special run and put it into a wooden bowl. let it cure for a few days to a few weeks. it is ready to use as soon as it solidifies, but it handles a bit better with some aging. it will never get as hard as a commercial bath soap, but doesn't need to, as you are not handling it like a bar of soap. after a couple of weeks mine is about the consistency of stiff putty- I can still dig it out of the mold with my fingers and press it into the soap bowl. it also has an odd soapy smell which fades with aging. you can scent it with whatever essential oils or fragrance oils you want. include the amount of essential oils or fragrance oils in soapcalc, but add them last thing, after it has cooled off, but before it is too stiff to mix.
some things to not put in your shave soap:
any oil high in oleic acid- ie olive oil.
clay. dries the skin and dulls your razor.
abrasive bits of stuff as exfoliant: ground up oatmeal, walnut shells, whatever. the razor does a great job exfoliating your skin as is, and bits of junk get between the razor and your skin and do nothing but mischief.
