Monday, June 16, 2008

Analyzing Ancient Polychromy on Greek and Roman Sculpture

I just returned from southern California where I was privileged to view the "Color of Life" exhibit at the Getty Villa about the use of polychromy to enhance ancient Greek and Roman sculptures. Although I must admit that I personally prefer the "classical" look of the unadorned stone, I find it interesting to view sculptures as they would have appeared to ancient residents of Rome and Athens. This head of the Emperor Caligula originally was thought to be painted with a dark red skin tone, almost the color of terracotta. But further research indicates the sculpture of "Little Boots" was more lifelike.

As a computer graphics enthusiast, I like to take an image of a colorless ancient sculpture and apply color and image maps to it to see what the real person the sculpture represents might have looked like. I used this technique on the sculpture of Alexander the Great on the right. I used Photoshop to apply color lightly with the transparency set to about 12% so the facial structure of the sculpture can "show through" and applied image map eyes. The best recreation using this computer technique I have ever seen was an image of Constantine complete with luminous blue eyes and a five o'clock shadow! I tried to find it again to link to it but alas it has been lost to internet history.

I was curious about the pigment analysis process that has been undertaken in the last few years to identify the colors and materials used by ancient artists and was pleased to find this brief article on such a project conducted in Denmark:

"A Greek marble sculpture (inv. No. 2830), dating from c. 425 BC (see archaeological comments) [1], from the Ny Carlsberg Glyptotek was examined to locate, analyze and document any remains of polychromy. Since only a few sculptures from this period with paint fragments have so far been examined there were no particular preconceptions about what might be found or identified [2]. Although it might be expected that some of the 15 to 20 pigments known and described in ancient sources, and which have been identified in previous studies, would be present, the nature of the binding medium used was less obvious. The methods of examination, analysis and documentation used are those commonly applied to polychrome sculptures from antiquity and medieval times.

A variety of methods was employed in this project, beginning with an examination of the stone surface by microscopy, followed by documentation using black and white, colour, infrared and ultraviolet fluorescence photography. On basis of these results, four areas on the sculpture were identified as promising areas for taking samples of paint.

One paint samples was taken from each of the four areas. Half of each sample was kept for further analysis while the other half was made into a paint cross-section. These were studied by dark field and ultraviolet microscopy, and photographed. This examination of the layer structure led to a further discussion of the possible composition and to the determination of the relevant analytical methods to be used in the next stage.

The cross-sections were studied in the scanning electron microscope and analysed using energy dispersive X-ray analysis (SEM-EDX). Backscatter images provided further information about the layer structure and EDX analysis provided information about the chemical elements present in the samples. The four cross-sections were further examined by Fourier transform infrared (FTIR) spectroscopy with attenuated total reflectance (ATR) microscopy, providing further information about the chemical composition and structure of the paint samples.

The visual examination of the surface, combined with photographic documentation, revealed that there were only very small fragments of paint left on the sculpture. Three types of paint were identified. First were minute flesh-coloured areas on the face, mainly on the left cheek just below the eye, on the right cheek next to the chin and beneath the left ear. Second, brown areas in recesses in the hair and, third, an area at the edge of the hair above the forehead with a dark brown colour on top of a grey-white layer — an area that is superimposed on a break in the surface.

Ultraviolet fluorescence revealed that the eyes had been painted. A prominent fluorescence in the white part of the eye bore witness to this, although no traces of colour, pigments or binding medium could be found. Furthermore, a yellowish ultraviolet fluorescence was seen on the marble surface where the flesh colours had been.

Three of the cross-sections, two flesh-coloured samples and one from a brown area of the hair, contained two layers, a calcium-containing ground (c. 20–40 μm thick) beneath a coloured top layer that mainly comprises a calcium-containing material with an iron compound and charcoal as the colourants. The main difference between the samples from the flesh and hair was in the proportion of charcoal and iron compound. The crosssection from the hair contained one large grain of charcoal.

Of note is the similarity between the paint structure for the sculpture’s flesh colours and that of analogous structures in mediaeval polychromy. The samples also show high homogeneity within the layer and relatively thin paint layers.

The fourth cross-section, from the hair above the forehead, contained a very thick, white calcium-containing layer. The colouring matter appears in lumps within, and on top of, the white layer, and contains iron, barium and sulphur. The presence of barium probably implies that this layer was applied to the sculpture within the last 200 to 300 years.

One of the questions that has yet to be answered is the nature of the binding medium used for the paints in this sculpture.

This 23 cm high fragment of a female head was acquired in Athens in c. 1910. The marble is Parian Lychnites and the statue is thought, on stylistic grounds, to be a Classical Greek original made in Athens around 425 BC, although an attribution to a later, Roman imperial, date cannot be ruled out.

Compared to the Greek Archaic and Early Classical periods, the sculptural polychromy of both the Classical Hellenistic Greek and Roman periods remains very poorly documented. The results related above have a particular bearing on one of the most contested issues, namely how the naked parts of marble sculptures were dealt with, either on Classical originals or Roman imitations. It should be pointed out that the traces of polychromy documented here may theoretically be later additions. Further comparative data must be accumulated in order to reach a firmer conclusion. In this regard, co-ordinated, systematic and, not least, interdisciplinary studies of museum collections are needed. Just as important is an increased awareness among archaeologists and conservators working in the field of possible, usually minute and very fragile, remains of polychromy on finds of sculpture and architectural elements. The need for an international forum dedicated to the subject of ancient sculptural polychromy is evident." - Mikkel Scharff, conservator and head of department at the School of Conservation of the Royal Danish Academy of Fine Arts, Copenhagen

See video "Tracing Colors of Ancient Sculpture"