Two of the most important elements of painting are color and technique. And while we can just take a trip to the local hobby store to purchase a rainbow of paint colors and learn the craft, painters in the past needed to source these elements themselves.
A set of remarkably well-preserved wall paintings in Cartagena is helping to expand what we know about Roman artistry. Researchers studying pigments from the Domus of Salvius have uncovered a mural technique, never before documented in Roman Hispania, that blends chemistry, craftsmanship, and cost-efficiency in ways that feel modern.
Published in Heritage Science, the findings suggest that 1st-century painters weren’t just artists, but were also skilled chemists.
“Roman craftsmen combined technical ability, knowledge of materials, and an aesthetic sense. Their methods also reflected the social status of the owners and the cultural tastes of the time,” wrote the study authors in their research.
The Roman “Recipe” For Long-Lasting Murals
At the center of this discovery is a clever pigment strategy that balanced aesthetics with practicality. The murals studied relied on a mixture of materials, including calcium carbonate for white, charcoal for black, goethite for yellow, and glauconite for green, along with traces of Egyptian blue. But the most revealing detail was in how the artists handled red.
Red pigments in Roman murals often depended on cinnabar, a vivid but expensive mineral sometimes called “red gold.” Researchers found that, in order to stretch this costly material, the painters of the mural mixed it with iron oxide.
“Iron oxide was a cheap material that was commonly used in workshops to create reddish tones. Cinnabar was more costly and had to be supplied by the client,” explained the research team in a press release.
Although the combination of these two materials wasn’t unusual, what set this technique apart was how it was applied. Instead of painting the red mixture directly onto the wall, the craftsmen of this mural first coated the surface with a layer of yellow. This underlayer acted almost like a primer, stabilizing the pigments and protecting the cinnabar from degradation.
“Cinnabar tends to blacken when exposed to light, moisture, and caustic environments,” the study authors stated in the press release.
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How Did Scientists Uncover This Painting Technique?
The discovery of this new technique came from a suite of advanced analytical tools that allowed researchers to break down the murals at a microscopic level.
Using X-ray diffraction, scientists identified the mineral composition of the mortars used in the walls. Meanwhile, Raman spectroscopy — a technique that detects chemical compounds based on how they interact with light — helped pinpoint the pigments themselves. To understand how those pigments were layered on the wall, the team used electron microscopy, which revealed the previously invisible yellow layer beneath the red paint.
Together, these methods exposed a level of technical painting that isn’t immediately obvious to the naked eye. The murals may look simple, but their construction shows a deep understanding of chemistry, material behavior, and environmental durability.
Connecting Roman History to Modern Science
The findings reinforce the idea that Roman craftsmanship was far more sophisticated than often assumed. While the Domus of Salvius likely belonged to a wealthy household capable of commissioning expensive materials, the research suggests that technical expertise played just as important a role as wealth.
The study also hints at a broader network of shared knowledge. Researchers proposed that such techniques may have been taught in workshops or preserved in early “recipe books” that circulated among artisans across regions. The team suggested this due to the fact that a similar pigment combination, as seen in these murals, has only been documented once before, in Ephesus, Turkey.
Overall, the new study highlights the growing importance of archaeometry — the intersection of archaeology and scientific analysis. By combining historical texts with laboratory data, researchers can reconstruct ancient practices with unprecedented detail, offering a clearer picture of past societies.
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