The ingredients for a basic batch of lye soap are lard or oil, lye, and water. Other ingredients such as color, fragrance, or essential oils can be added as well to alter the characteristics of the soap.
To make a basic batch of lye soap, mix 4.4 ounces of lye crystals with 7 ounces of water. Once the mixture has dissolved completely, While the mixture cools, begin heating 2 pounds of lard. Once the lard has reached 90 degrees Fahrenheit and the lye mixture has cooled to 85 degrees Fahrenheit, mix the two together slowly and stir with a plastic or wooden spoon until the mixture is emulsified.
The emulsification process takes between 30 and 60 minutes. At this point, fragrance, color or essential oil can be added. Allow the soap to harden in the mold for several days, and then wrap the soap in brown paper and allow it to cure for at least four weeks. To test the soap, use it to wash your hands. If the soap leaves a slimy film, rinse your hands with vinegar and allow the soap to continue to cure in the brown paper for an additional two weeks before checking it again.
Once the process is completed, wash all of the materials and equipment that were used in the soap making process with hot, soapy water, and rinse them with a bit of vinegar to make sure all the traces of lye are completely removed.