Tallow, or animal fat, along with lye, remains a basic ingredient of soap. Fat reacts with lye—a substance made in ashes that can be pretty toxic, which is why soap makers need to wear protective gear—in a process called saponification. The story is that the drippings and ashes from the cook fires of the gods rolled down the hill and were discovered by filth-encrusted Romans.
Modern soap makers—at least those working in small, artisanal operations—use the same techniques. The saponification process yields a thick slurry. As it solidifies, fat neutralizes the caustic lye. Rubbing your hands together while washing allows dirt to temporarily bond with the water and soap and get washed away. The same process occurs with most viruses and bacteria that might be lingering on your hands.
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 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. Nini likely grew up lower class because in addition to being a housekeeper she had a far more modern role.
According to the Assyriologist Benjamin Studevent-Hickman, thanks to as many as ten thousand laborers a single textile factory in Ur produced more than four hundred tons of wool in a single year. Nini, it seems, was one of these workers. The first documented use of soap is described on a cuneiform tablet found in Girsu. According to chemical archaeologist Martin Levy, the tablet was written 4, years ago and concerns the washing and dyeing of wool.
To properly dye wool, a weaver must remove the lanolin fats from the textiles, which is accomplished far more easily with soap. Even today, weavers wash freshly sheared wool in soapy water to remove the lanolin. Nini was far from the first person to take advantage of the chemical reaction between alkalis and fats—what chemists call saponification. The ingredients are common enough that most scholars suspect someone long before Nini first created the reaction accidentally, according to Seth Rasmussen, a professor of chemistry at North Dakota State University with whom I spoke.
Alkalis are found in the ashes of burned wood and many scholars believe early humans used wet ash to clean greasy butchering tools. Unbeknownst to the cleaner, ash combined with the animal grease to create a simple, impure soap. The fact that wet ash removed grease was probably understood by the first weavers as well, who likely used it to clean their textiles, according to Hugh Salzberg, author of From Caveman to Chemist. It may seem a small step, but it meant Nini no longer relied on the grease of whatever she was washing to aid in the reaction.
Instead, she could create the ideal mix of fats and alkalis and wash anything—especially, and most critically, human hands. Eventually, and up through the Middle Ages, soap makers skipped the strainer and dipped sacks of ash into water like tea bags.
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