Interdisciplinary network for basic research
"We know that colour was an integral part of all Greek and Roman sculptures", says Jan Stubbe Østergaard, Research Curator of ancient art in the Ny Carlsberg Glyptotek, Copenhagen. "But we are far from really understanding this phenomenon." Of the thousands of antique sculptures in museums all over the world, only relatively few have been studied in-depth with regard to their polychromy. The aim of the Copenhagen Polychromy Network, an interdisciplinary research team consisting of the Ny Carlsberg Glyptotek, the School of Conservation of the Royal Danish Academy of Fine Arts, the Geological Museum of Copenhagen University and the Institute of Chemistry of the Technical University of Denmark, is therefore to conduct research on sculptures in the Glyptotek and document traces of colour. The matter is urgent because such traces are gradually disappearing.
Microscope images the only evidence
The microscope is the most important tool of conservator Maria Louise Sargent, as some of the remains of paint on the sculptures are so minimal that samples cannot be taken. "The only evidence of color is what I see through the microscope", explains the conservator. "So it’s vital that I examine the sculpture systematically to enable the pigment traces to be found again at any time." Maria Louise Sargent uses a surgical microscope and a digital microscope.
"The digital microscope offers great flexibility", says the conservator. "The statues are up to two meters tall and we have to scan every centimeter. What’s more, the digital microscope can magnify up to 160x. The color pigments and residues of the original paint are no more than traces and we are now able to detect them more easily and analyze them in detail. The digital technology allows us to record videos and images and show them on a monitor for discussion." After having examined the areas with paint residues on the monitor, digital images are recorded for documentation.
Cooperation with British Museum
In her search for traces with the surgical microscope, Sargent found infinitesimal remnants of blue paint on a Greek limestone figure made around the year 580 BC. For the identification of the pigment, the Danes are setting their hopes on their coming collaboration with the British Museum. The "giant" of Europe’s museum landscape has started a polychromy project on the model of the CPN and works together with the CPN as external research partner. "Our colleagues at the British Museum have developed a non-invasive method of detecting Egyptian Blue using UV photography. We’re hoping this will give us more information", says Østergaard optimistically.
Traces of 2,000 years revealed
Currently, Maria Louise Sargent is working on "The Beauty of Palmyra". The limestone statue from Palmyra in Syria dates from around 190–210 B.C. It was decorated with rich jewelry, which may have held a glass ball in its center. "The works of art are over 2,000 years old, and they have quite a story to tell", says Sargent. "That is to say, I can see a lot of traces, including traces of pollution or aggressive cleaning agents. The difficult part is to identify the traces correctly." After all, the ancient painters used materials like red ochre as a colorant, which is an earth color. So what is paint, and what is just earth from the find spot? Charcoal was used for the black color, but modern air pollution is indicated by carbon particles, too.
A controversial point: Was skin coloured or not?
Just looking at the Greek portrait currently under examination with the naked eye, we can see various traces of colour in the pupils, on the eyelashes and the lips. Østergaard is hoping for really important discoveries: "The examination of this object may help to solve the problem of whether skin on ancient sculptures was painted or not. To date, we have only one single proof from the Classic and Hellenistic periods that a body was painted skin-coloured."
Physical analysis reveals origin of paint
If enough paint is found, tiny pigment samples are taken and examined in cross-section under the materials testing microscope to determine layer structure and if possible identify pigments. Some are subjected to physical analysis by CPN partner institutions. It was thus possible for Minik Rosing of the Geological Museum to pin-point the origin of a pigment by an analysis of the isotopic trace elements: "The red lead oxide of one sculpture came from Spain and was exported to Rome", says Østergaard. "This tells us something about ancient trade routes as well."
Still a lot to do in polychromy research
Although the CPN has already delivered significant research results, polychromy research is still in its early stages. "Even though we can identify colors on antique sculptures, we don’t know what they really looked like", says Østergaard. "We need to know a lot more about the refined details of technique and about the esthetic effects of the ancient polychrome works of art."
The new discoveries made examining the many sculptures of the Ny Carlsberg Glyptotek with the microscopes will be shown in a large exhibition in Copenhagen in 2012.