Could one of the oldest and most popular eyeliners have precipitated a world-changing innovation in chemistry? Philippe Walter, founder and director of Sorbonne University’s Laboratoire d’Archéologie Moléculaire et Structurale, says yes, this is exactly what happened some 4,000 years ago.
Ever since then, particularly in parts of North Africa and West and South Asia, kohl has been in continuous use. Today it can be found just about everywhere, but until relatively recently, nobody understood the innovation that went into the making of kohl nor the extent of the cosmetic’s therapeutic effects.
The Arabic term kohl—known as kuul in the Horn of Africa, kajal in South Asia, sormeh in Persia—today denotes the eyeliner that Egyptians, around 2000 BCE, called mesdemet, a word that meant, “mineral powder to render the eye expressive,” says Walter. And not just in terms of beauty or personal expression: Mesdemet conferred upon its wearer the eye of Horus, the god whose properties included protection, healing and wholeness. We may consider King Tutankhamun’s kohl-lined eyes regal, but to his fellow Egyptians, mesdemet made them “emanations of the god’s eyes,” as Walter puts it.
Today, kohl carries a wisp of this old meaning in such practices as applying a bit of kohl on children to protect them from the evil eye. Kohl also retains some of its associations to health, as when men and women use it to reduce the hazards of sun glare. A 2009 paper from the Department of Pharmaceuticals at the University of Karachi, Pakistan, confirmed that when the shiny mineral particles found in Egyptian kohl mingle with the watery film that covers the cornea, they help protect the eye from ultraviolet rays. Mostly, however, kohl is now used for beauty. To women, performers and their makeup artists worldwide, kohl is one of the most versatile tools in their kits, allowing them to create pretty much any kind of look they can dream up: You name it, someone somewhere has “kohled” it.
The traditional way to use kohl has changed little over the millennia. Dip a stick-like applicator into kohl powder, and then place it along the inside of the lower eyelid or water line. Squeeze the eye shut, and pull the applicator out toward the temple, thus coating the inner rim. Egyptians were also the first to mix powdered kohl with oil and other emollients. They then used the applicator more like a palette knife to outline the exterior contours of the eyes, varying the coverage area, shape and line to whim, fashion or need. Present-day kohls tend to be both silkier and more smudgy than other types of eyeliners, and just as mesdemet did in Egypt, today’s kohls come in many different varieties.
Archeologist Jolanda Bos, author of Paint it, Black: A biography of kohl containers, points out that hieroglyphics on some Egyptian cosmetic containers describe their contents and can even seem to promote them. These vary from “this is very good kohl of such-and-such quality,” she says, to naming what appear to be ingredients, many of which remain uncertain.
But to Bos, the containers speak volumes about daily life, particularly the “little reed containers.” Simple, made of an easily available material and therefore cheap, Bos says, they served as “single-use packages for kohl that you take home and you empty out in your own beautiful glass container” or, if you could not afford glass, use as is. “I realized there’s a whole economy behind kohl,” she says, from the procurement of materials to the development of formulas to promoting and selling different mixtures with words like, “very good quality” or “a kohl you have to apply in summer.”
So what was mesdemet made from? For a long time, many thought it was primarily soot, along with finely ground minerals, often believed to be stibnite, a natural mineral source of the chemical element antimony. But in the late 1800s, Egyptologists found that the metal most commonly used in kohl was lead, which today rings public-health alarm bells. Subsequent studies showed that most frequently, the lead came from galena, an ore that Egyptians ground to a fine, shimmering powder. Mixed with a variety of other inorganic as well as organic substances including plant-based soot, it created varied hues of grays and blacks. Kohls today are as diverse a mix as then, with many mixing in minerals, oxides, carbonates as well as, still, lead.
This makes Walter’s research all the more eye-opening. In the late 1990s, as a young researcher of restoration science at the Louvre, he became fascinated by the magical powers Egyptian texts ascribed to kohl. The Louvre’s collections held plenty of samples to study: dozens of cosmetic containers, some still filled with kohl, others with remnants, all dated between 2000 BCE and 1200 BCE. “Nobody had studied this since the 1950s,” he says. “I thought, ‘We have better equipment now, so maybe we’ll gain a new understanding.’ And I was not disappointed.”
Most of the 50-or-so samples analyzed by the team contained two minerals that “only form under very particular geological conditions” and thus “very rarely occur naturally,” says Walter. They are called laurionite and phosgenite, and their presence in sample after sample could only mean one thing: They had been manufactured.
Though no Egyptian description of the process has been found, some descriptions appear in first-century-CE writings by Pliny the Elder and in Dioscoridis’ De Materia Medica. The procedure involved immersing a natural lead oxide found on galena in water and monitoring the water’s salinity for some 40 days. When Walter and his team did this in the lab, the precipitate was none other than laurionite. When they started off with natron, a powdery sodium carbonate used in mummification, the result was phosgenite.
“Fire-based technology has been used to manufacture Egyptian blue pigments since about 2500 BC,” their study concluded. “We have now shown that wet chemistry was used as long ago as 2000 BC.” This was a discovery: Instead of using heat to trigger a chemical reaction, Egyptian chemists had figured out how to induce reactions using water. This technique has proven fundamental to science ever since.
But what would have prompted Egyptians to try doing it at all? And even after learning how to do it, why would they have invested so much time and effort in creating these particular ingredients for a cosmetic? Walter points to the environment and kohl’s medicinal use.
Every year, the Nile flooded, flowing not only into the fields of the Nile Valley but also into bodies of water such as the saline lakes of Wadi El Natrun. The resulting annual, natural chemical interactions between the saline water and the lakebed’s limestone offered opportunity to observe and imitate nature, explains Walter.
Instead of using heat to trigger a chemical reaction, Egyptian chemists making kohl learned to induce reactions using water.
Egypt also was known far and wide for its expertise in treating eye ailments, and multiple studies have shown that kohl was part of Egyptians’ medical kit. A 2009 collaboration between Walter and fellow French chemist Christian Amatore, at the time a professor at Centre national de la recherche scientifique, uncovered an astonishing property in this cosmetic. Their study used microelectrodes to investigate biological mechanisms at the cellular level, a technique Amatore had pioneered.
Testing the synthesized chlorides found in kohls, they found them “ever so slightly soluble in the fluid of the eye,” Walter says. As a result, “the cells of the eye were not poisoned or killed by the presence of lead.” Further testing of the laurionite showed that its very low concentration of lead also tricked the body’s immune system into dispatching bacteria-fighting macrophages and phagocytes. This equipped the kohl-user’s eyes with defenses against bacterial infections.
When people noticed that using kohls with laurionite led to healthier eyes, Walter speculates, that spurred production. Such empirical observation would also explain why some kohl containers specify the times of year for which a particular kohl is best suited.
“And that means they had an extraordinarily well-developed pharmacopeia,” says Walter. It included a preventive medicine and immunotherapy, not to mention one of the earliest windows into the workings of the eye—a subject we will look into more in the next installment of the Ingenuity and Innovations series.