Ancient Egyptians used pigments to create dyes and paints, but the origin of one blue pigment was lost to time. This dye was regularly found on artefacts from ancient Egypt, and still used by the Romans. After that, though, it was gradually used less and less until nobody remembered how to make it. But now, researchers from Washington State University have recreated this blue pigment.
The researchers worked with the Carnegie Museum of Natural History and the Smithsonian’s Museum Conservation Institute. After studying the blue pigment on materials from museum collections, they made their own version of it with different recipes using silicon dioxide, copper, calcium, and sodium carbonate. They shared their recipes in a research paper last month.
Egyptian blue is different from many other ancient pigments, because it wasn’t a pigment found in nature. So rather than trying to find the plants or minerals that naturally produce this blue, the search was on for the lost recipe that would have created this bright blue.
Everything the researchers tried would have to resemble methods that people would have access to 5000 years ago. So to heat the materials, they had to limit the temperature to about 1000 degrees Celsius (about 1800 degrees Fahrenheit). That sounds pretty hot already, but modern industrial furnaces can reach much higher temperatures.
After doing a chemical analysis of the pigments they produced, the researchers compared this to samples they took from museum artefacts. For example, they measured the exact wavelengths of both visible and near-infrared light that are characteristic of the pigment.
One thing they noticed was that there wasn’t just one version of Egyptian blue. Often the pigment was mixed with other materials and just slightly different based on where or how it was made.
“You had some people who were making the pigment and then transporting it, and then the final use was somewhere else,” John McCloy, lead researcher on the study, told Washington State University. “One of the things that we saw was that with just small differences in the process, you got very different results.” But often these differences didn’t have a big effect on the color. Even with only 50% of the blue pigment, the color dominated over other materials in the mixture.
The newly created pigments are now part of the collection at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. But there could be more to these ancient blue pigments.
“It started out just as something that was fun to do because they asked us to produce some materials to put on display at the museum, but there’s a lot of interest in the material,” said McCloy. Egyptian blue has caught the eye of people who are interested in using it for new technological applications, because the pigment produces near-infrared light that could be used for fingerprinting in forensic science or for security solutions such as counterfeit-proof inks. But even without these modern applications, the recreation of Egyptian blue gave an insight into a long lost recipe for the world’s first synthetic pigment.