Soap is a mixture of acid and alkali. At a rate that makes cleaning as well. And do not harm the skin is slightly acidic with a ph between 8-10, or acid oil. Such as vegetable oils, animal fats, alkali such as sodium hydroxide, in general, the ratio when is the right blend of acid oil should be left for about 5% if no tool to measure the ph to collect soap for at least 15-30 days to make the ph. decrease in the rates reasonable.