It's a lot of work to make, but it's also a lot of fun. It is a good use for huge quantities of fat left over from cooking something. When the soap is firmer but not yet hard, cut into bars with a knife. Wrap in clean cotton rags and store in a cool, airy place for 3-6 months. The recipe will work equally well with other animal fats to produce a similar result.
Coconut oil yields a softer, quick-lathering soap.
Olive oil and other vegetable cooking oils yield a very soft soap that never completely hardens. Unfortunately, these oils are sensitive to air and light, and soap made from cooking oils will spoil in a few weeks unless it is refrigerated. Let this mixture sit for a few weeks, stirring it every day, then heat in a double boiler for 10 minutes, then cool and strain the oil. The soap works just fine with no fragrance at all, and many people prefer it that way. We have all seen the oatmeal soaps in the store that cost a fortune.