How the Inca Discovered a Prized Pigment

In 1908, at a lab in Niagara Falls, New York, a metallurgist named Auguste Rossi invented a brilliant white pigment that would become almost ubiquitous in human-made stuff and is found today in everything from paint to plastic to pills. The chemical, titanium dioxide, became what color researcher Matthijs de Keijzer calls the “most significant contribution” to an explosion in 20th-century pigment technology, in what some historians refer to as a chromatic revolution, a new look for the world. But archaeologists say that Rossi didn’t get there first.

In 2018, researchers in the United States discovered titanium white in 400-plus-year-old ceremonial wooden drinking cups made by the Inca and residing today in various museums. Carved with elaborate geometrical designs, the cups, called qeros, traditionally were not colored. But around the time of the Spanish conquest of Peru in 1530, the Inca started mixing pigments, including titanium white, into resin and decorating qeros with the bright goo.

In the Americas, white pigments were usually calcium carbonates—lime or chalk. In Europe, they were lead white. How did the Inca jump 400 years into the future?

The answer might be the Giacomo Deposit, an unusual mineral sand deposit near the border between modern Chile and Peru that’s full of naturally occurring titanium dioxide and silica. And the Inca had access to it. “It’s just an extraordinary deposit,” says Emily Kaplan, a conservator at the Smithsonian National Museum of the American Indian, who studies the qeros. “We obtained a sample of the ore and compared it to white from the qeros,” Kaplan says, “and it was super-similar.”

Finding titanium white on even just a handful of qeros has rewritten the history of color, says Marilyn Laver, an independent conservation scientist who has published extensively about titanium white. The natural version of the pigment that the Inca used “might not have had the same optical properties as the modern pigments,” she says, because those are subjected to chemical processing, but would still have had the bright whiteness and opacity that calcium carbonates and lead white lack.

Even so, by 1570, the Inca had stopped using titanium dioxide. Last year, Kaplan and her colleagues learned that Incan craftspeople switched to lead white, which the conquistadors brought from Europe.

Adam Rogers | READ MORE

Adam Rogers, a deputy editor at Wired, is the author of Proof: The Science of Booze.