The word 'soap' was derived from Mount Sapo which was a location for animal sacrifice. Melted animal fats and wood ashes would be washed down from the mountain and, in the clay along the banks of the River Tiber, a crude soap would form. People found that washing their clothes in this water would result in cleaner clothes. Little has changed in the chemistry of soap making since these early beginnings.
Soap is made by reacting fats and oils together with lye. The fats and oils may be animal or vegetable in origin and the lye may be a solution of caustic soada (sodium hydroxide) or caustic potash (potassium hydroxide) dissolved in water.
You may have heard that most soaps are made with caustic soada and then, on having heard this, become alarmed, wondering what these soaps have been doing to your skin. Even if a soap is made using caustic soda, a well made soap, once it has 'saponified' and matured properly, will not contain any caustic soda. All of the caustic soda will have reacted with the other ingredients in the soap and undergone a chemical reaction which completely changes its chemical structure and properties.
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