Is Soap an Acid or a Base?

Soap is a base consisting of metallic salts, usually in the form of sodium, from fatty acids. The first soaps consisted of water, oil and lye, which gave the soap its alkaline nature and reacted with the oils to form the soap.

Soap makers use sodium hydroxide or potassium hydroxide to make soaps, with the sodium variety used for solid soaps. Cream soaps use a blend of the two bases. Making soaps that are gentle enough for daily use while strong enough to clean effectively has long been a balancing act for soap manufacturers, as stated by the U.S. Department of Energy.