The making of soap dates back at least 5,000 years to the Sumer region (now southern Iraq) in Bronze Age Mesopotamia. Sumerian texts from that era give brief descriptions of ways of making soap from the resin of conifers such as fir trees.
These techniques were later expanded by the Babylonians and Egyptians, who devised new forms of soap made from plant ash, oils and animal fat. The end result had the same basic properties as modern soaps: when combined with water and agitated they created a lather and helped remove dirt.
Soap originally seems to have been used primarily for the treatment of ailments. One Sumerian text dating back to 2200 BC describes a form of soap being used to wash a person who seems to have had some type of skin condition. Exactly what the physicians believed this would do is unclear, but the idea that soap had medical benefits was accepted by many ancient civilisations.
It’s now known that they were on to something. In creating soap, they had stumbled upon a way of producing a substance made from dirt-removing, tadpole-like molecules.
When mixed with water, these molecules form spherical structures called ‘micelles’ around any droplets of germy dirt or oil, with their water-hating (‘hydrophobic’) tails pointed inwards and their water-loving (‘hydrophilic’) heads pointed outwards. The outside of the micelle is soluble and so it washes away, along with any grime trapped in the middle.
Robert is a science writer and visiting professor of science at Aston University.