Tuesday, March 14, 2023

Kohl: Beginning of Wet Chemistry

Environmental & Science Education, STEM, Science & Society, Culture, History of Science, Nature of Science, Archeology, Health, Medicine

Ed Hessler

There are eye liners and there is eyeliner, one that is unique among them: Kohl, also known as mesdemet, which was invented and marketed by the Egyptians. It was a "mineral powder (made) to render the eye expressive." Its history - it dates from ca 2000 BCE) and what has been learned about its use is the first in a new feature of Aramco World  for January / February 2023: Ingenuity Innovation (link below).

Lee Lawrence's story includes a small album of photographs from museum collections--a gilded sarcophagus, busts, painting, a make-up kit, kohl pots, portable kohl tubes, jars, a frieze showing the way the eye was depicted in Egypt, a wooden coffin box with the protective, kohl-lined eyes of the god Horus or as it is put in the article, "emanations of the god's eyes.

And the story reveals how residue left in kohl jars was used by Philippe Walter, founder and director of Sorbonne University's Laboratoire d'Archeologie Moleculaire et Structural. To Lawrence's opening question, "Could one of the oldest and most popular eyeliners have precipitated a world-changing innovation in chemistry," Walter answers yes. And when did this happen? Almost 4000 ybp.

First, Lawrence reviews old meanings and practices, for beauty, how it is applied - a small applicator is placed along the inside the lower eyelid or water line, the eye is then squeezed shut and the applicator is pulled out towrd the temple to spread it, cosmetic containers which appear to promote their use and also describe their ingredients, colors and hues, seasonal uses of different kohl, what certain containers suggest about daily life, and the likely economy developed.

It wasn't until the late 1800's that the most common metal found during analysis was lead. This doesn't sound like a good thing given what we know about the health effects of lead. Walter's group, using modern techniques, analyzed some 50 samples and found two minerals common to the samples, minerals "that formed under very particular geological conditions...very rarely occurring naturally, laurionite and phosgenite. This led to the conclusion that they were manufactured.

While no Egyptian descriptions of the process have been found, two first century CE authors, Pliny the Elder and Dioscoridis described a description of the process leading to laurionite. Phosgenite was made with natron, "a powdery sodium carbonate used in mummification."

And the Walter team concluded "We have now shown that wet chemistry was used as long ago as 2000 BCE. Wet chemistry is using water to "induce reactions" rather than heat from fire.

Of course we want to know what led to this breakthrough and Lawrence "points to the environment and kohl's medicinal use" for supporting evidence. The annual flooding of the Nile Valley and also into saline lakes resulted in "natural chemical interactions between the saline water and the lakebed's limestone(which) offered opportunity to observe and imitate nature." Egypt was known for "treating eye ailments, and multiple studies have shown that kohl was a part of Egyptians' medical kit".

Reading this article is likely to make you think of our remarkable curiosity which leads to understanding about how the natural world works and innovations derived from such research. This story of kohl smacks of the practices of science or, at least, the practices of proto-science.

A PDF may be read here. The first image that greets you will dazzle you.

Lawrence's reporting is at the top and I highly recommend you have her guide you rather than me through the world of kohl. I wanted to provide some reasons to read it.


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