There was a time when the perfect smile had nothing to do with teeth whitening or peroxide adhesive strips. Let’s talk about the Iron Age in Vietnam, when a beautiful smile meant exactly the opposite: teeth as black as night, shiny as mirrors. A fashion that seems bizarre to us today, but which at the time represented a precise aesthetic and cultural canon. Now, thanks to a study conducted by the Australian National University and published on Archaeological and Anthropological Scienceswe finally know the details of this ancient and fascinating practice.
The mysterious paste that colored smiles
For years, archaeologists had been faced with a conundrum: those skulls with the strangely dark teeth found in Vietnamese archaeological sites told of a widespread custom, but no one could understand whether that color was intentional or the result of eating habits, such as chewing betel nuts. The difference is not insignificant: betel nuts, palm seeds with psychoactive effects that are widespread in Asia, can actually darken enamel, but they tend towards brown, not the intense black that scholars observed on those ancient teeth.
Yue Zhang, first author of the research, explained it bluntly to the magazine Science: Chewing betel leaves you a brownish color, nothing like that deep, shiny black. So, there had to be more. To find out, the team analyzed three skulls from Dong Xa in northern Vietnam, dating between 1800 and 2200 years ago. And here comes the best part: they used a chemical imaging technique that revealed traces of iron and sulfur trapped in the enamel. One tooth in particular had very high concentrations of iron oxide, an unmistakable sign that someone had repeatedly spread a paste on that surface.
It wasn’t mineral-rich soil, it wasn’t the random result of chewing. It was very much a cosmetic treatment, applied over and over again over the course of weeks. In practice, a sort of nail polish ante litteram, but for teeth.
The chemistry hidden behind the shiny black
Reconstructing the exact recipe for that pasta was not easy, but the researchers succeeded. The ancient Vietnamese they heated plant extracts rich in tannins – such as gall nuts or pomegranate peel – together with iron salts. The chemical reaction between iron and tannins generated intense black pigments, which were then spread on the teeth like varnish. The process required patience: the application had to be repeated over several weeks, allowing the paste to set on the enamel. Finally, as a final touch, the coconut tar gave that shine that made the smile not only black, but shiny.
In short, a real beauty routine, elaborate and sophisticated. Zhang also speculated on how they could obtain the ingredients: «The Iron Age is the period when people had the most access to iron, in the form of mines, tools or weapons. Sulfur, on the other hand, is everywhere in nature. They probably crushed the vegetables and placed them on an iron blade, waiting for the chemical reaction to occur.”
Why were black teeth so prevalent
This discovery isn’t just about Vietnam. Other cultures, in Africa, Oceania and Asia, have adopted similar practices, albeit with different techniques. The reasons? They varied a lot. In some cases, dyeing one’s teeth served to distinguish oneself from animalsgiven that humans were the only ones who could afford such a striking aesthetic change. In others, it was a real symbol of beauty, social status or belonging to a group.
In Vietnam, however, the practice has taken on a particular complexity, almost becoming an art form. It wasn’t just a question of darkening the teeth: it was necessary to obtain that intense, uniform, shiny black. A technical challenge that required empirical chemical knowledge, patience and access to specific materials. And all this, let’s remember, without any notion of modern chemistry. They knew what worked because they had experimented, generation after generation.
Even today, in some remote regions of Southeast Asia, some continue to practice this custom. It is no longer as widespread as it once was, but it remains as a trace of a past that we have not yet finished understanding.
