Analyzing Roman wall paintings

BY CAROLINE ROBERTS, Conservator, Kelsey Museum of Archaeology

When I think about color in antiquity, I like to imagine how colors have weathered, or changed chemically over time, and the ways these changes impact how we see ancient paint surfaces. Ancient paint can be found on terracotta figurines, marble sculpture, and – most visibly – on wall paintings. The Kelsey Museum preserves a number of Roman wall painting fragments, and Curator and Professor Elaine Gazda has incorporated these artifacts into her history of art classes. One of Professor Gazda’s students, UM senior D’Arcy Cook, has taken on the challenge of identifying the pigments from a group of these wall painting fragments.

D’Arcy is a chemical engineering major who is interested in archaeological chemistry and conservation science. Her primary research question was whether pigments on the Kelsey wall painting fragments matched what she had learned to expect based on published literature. To answer this question D’Arcy used analytical techniques available in the Kelsey Conservation Laboratory and across campus. I felt this would be a great opportunity to learn more about artifacts in the Kelsey collection and to provide D’Arcy with experience analyzing ancient materials.

Using a scalpel, I removed milligram-sized samples of paint from the fragments. D’Arcy analyzed the samples using Fourier Transform Infrared Spectroscopy (FTIR), an analytical technique that identifies materials by detecting signals produced by their molecular bonds. Among other results, her analysis confirmed that Egyptian blue is present on one of the fragments – a pigment I also detected with a modified camera, and which we both observed using a polarized light microscope. Egyptian blue pigment was commonly used by the Romans on wall paintings and sculpture.

This project illustrates how technical research works best by incorporating multiple, cross-checking analytical techniques, and depends on scientists, art historians, and conservators to happen. Many thanks D’Arcy, to Elaine and the Kelsey curators, and to the UM Chemistry department and EMAL laboratory for their help with this research!

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Figure 1: Sampling photograph showing plaster and paint layers

 

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Figure 2: Visible (VIS), infrared reflected (IRR), infrared reflected false color (IRR-FC), and visible-induced infrared luminescence (VIL) images. The white luminescence in the VIL image shows the presence of Egyptian blue.

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