By Sama Marwan,
When Mount Vesuvius erupted in 79 AD, Pompeii was buried under ash. However, an unparalleled collection of frescoes was discovered after the city’s destruction, along with evidence of painting workshops, which have drawn special attention from archaeologists.
The first site is the residence of a paint merchant, known as the “House with the Workshop.” This house contained the largest stockpile of paints ever found in Pompeii, including 150 vessels alongside other tools such as stone pestles, scales, spoons, and a sharpening stone. As a sign of the sudden halt in work, red and black paintings on the wall record the workshop’s activities.
The second site is the “House of the Painters at Work,” a private residence. During excavations in the 1980s, archaeologists found 50 small ceramic pots containing pigments, as well as an imprint of a basket used by painters to transport pots between workshops. The decorative designs and unfinished preliminary sketches—interrupted by the volcanic eruption—allowed researchers to gain a better understanding of painters’ working processes at the time.
A recent study conducted at the Pompeii Archaeological Park did not focus on the frescoes themselves but on the paint. By analyzing 26 pigments—some of which had never been studied before—the findings, published in the spring issue of the Journal of Archaeological Science, examine the mineral chemical composition of the pigments, shedding light on how they were prepared before being applied to Pompeii’s house walls.
After previous studies confirmed the degradation of Pompeian pigments, researchers used digital microscopes at the site—an innovative, non-invasive approach. This revealed “the remarkable expertise of Roman painters in mixing and processing different raw materials to achieve a wide range of subtle shades.”
Pompeii’s paint workshops relied primarily on two pigments more than any others: Egyptian blue—a complex mixture of sand, copper minerals, calcium carbonate, and ash—and red lead, produced by roasting white lead. For instance, Egyptian blue served as a base for gray and was used to lighten yellow and green shades. Red lead not only enhanced red ochre but also served as a starting point for various pink hues and functioned as a corrector for purple tones.
The researchers noted that the extent to which artisans adjusted firing times, modified pigment particle sizes, and added white pigments to achieve the desired shade of blue was previously unknown.
The study also uncovered a previously unknown light green pigment, created by mixing red ochre, Egyptian blue, and a substance containing barite and alunite—sulfate deposits formed around volcanoes through pressure, heat, and water. This represents the earliest known use of barium sulfate as a primary coloring agent in the Mediterranean.
The researchers concluded that the comprehensive detailing of the pigments used in Roman paints now allows restoration experts to recreate these mixtures to match the originals, “ensuring that restored sections of frescoes remain chemically and visually consistent with the original artworks.”
