A study last fall by researchers at the National Institute of Optics-National Research Council of Florence (CNR) revealed that the intense red color in many of the stunning frescoes of the ancient Roman world–at sites such as Pompeii and Herculaneum–is really yellow in disguise.
Red like that inside the extraordinary Villa dei Misteri in Pompeii and other archeological sites was, in several interiors, obtained from ochre and thus yellow in color–a yellow that contact with high temperature gases during the eruption of Vesuvius in 79 A.D. altered to the color we call ‘Pompeii red.’
This color mutation phenomenon has been noted before by scientists, but never proven prior to this study. In that ancient era, CNR explained, red pigment was obtained in one of two ways: either from the rare and costly cinnabar (red mercury) and minium (red lead), or by heating up the readily available yellow ochre. On walls where lead and mercury were absent, CNR scientists determined that the red seen today was yellow when it was applied millennia ago. In all, the number of individual true Pompeii red walls has lowered by about 80, amounting to an estimated 150 square meters of surface.
The extensive use of rare and dear red pigment as further evidence of the wealth and prosperity of Pompeii and Herculaneum will have to be reconsidered in light of the findings. That these two cities were prosperous (Herculaneum in particular was a kind of luxurious resort town for the wealthy) is not in question. Yet it would seem inhabitants painted their towns a lot less red than archeologists have long believed.