Romans scraped themselves clean for centuries before adopting soap
Ancient Romans cleaned their bodies by rubbing in oil and scraping it off with a curved metal blade called a strigil. Soap arrived late; Pliny the Elder called it an invention of the Gauls. Yet soap-like mixtures of fat and ash had been made in Babylon nearly three thousand years earlier.
The oldest evidence of soap-like production dates to about 2800 BC in Babylon, and a Sumerian clay tablet from around 2500 BC records heating oil with wood ash to wash wool. Egypt's Ebers papyrus, from 1550 BC, describes combining fats with a natural soda called trona to make a medicine. These early proto-soaps differed from true soap, which foams, is made deliberately and can be produced hard or soft through understanding of alkali sources. Nobody knows who first made it, and several societies may have arrived at it independently.
Chemistry explains why it works. Soap molecules have one end attracted to water and one attracted to fat. In water, they cluster into tiny spheres called micelles, with greasy dirt trapped inside, so rinsing carries the grime away. Makers produce it by treating fats or oils with a strong alkali such as lye, which splits them into fatty-acid salts and releases glycerol. Sodium gives firm bars, potassium soft or liquid soap, and in hard water soap forms scum instead of lather.
Galen, the 2nd-century physician, rated Germanic soaps best and those of Gaul second. During the Islamic Golden Age, soap-making in West Asia and North Africa became an established industry producing hard, pleasantly scented bars, and al-Razi wrote down recipes along with a method for extracting glycerine from olive oil. The word alkali itself descends from the Arabic for ashes. By the 13th century cities such as Nablus, Fes, Damascus and Aleppo were important centres. Across the Levant, olive oil was boiled for days in copper cauldrons with plant ash.
Europe had its own tradition. Soapmakers in Naples belonged to a guild by the late 6th century, and around 800 Charlemagne listed soap among the products stewards of royal estates had to account for. China took a different route, using seeds of the Gleditsia tree as a detergent for over 2,000 years along with zhuyizi, which blended plant ash with pig pancreas, while fat-based soap appeared there only in modern times.
Source: Soap
