Investigating color on a Roman-Egyptian mummy portrait

BY CAROLINE ROBERTS, Conservator, Kelsey Museum of Archaeology

This week a team from the Detroit Institute of Arts conservation department traveled to the Kelsey to take a closer look at one of our Fayoum mummy portraits. The portrait is normally on display in the Dynastic Egypt gallery and is dated to the Roman period of Egypt (79 – 110 AD). The woman featured in the portrait is clearly of means, as her gold earrings and necklace, colorful gems, and purple robe indicate. We were curious to learn more about the colorants that were used to paint her portrait and to look for painting details that have become harder to see over time.

Christina Bisulca, conservation scientist at the DIA, brought along a portable spectrometer to identify pigments on the painting. She found evidence of pigment mixtures in multiple areas of the portrait, including the flesh tones, the oval gem at the center of the woman’s pendant, and the drapery of the robe. It appears that the various shades of purple in the robe were likely created by mixing and laying blue and red pigments and dyes, for example. Further analysis is needed to verify these results.

Aaron Steele, the DIA conservation department’s imaging specialist, brought along their powerful infrared camera to see if underdrawing might have been used to sketch the sitter before paint was applied. Although underdrawing was not immediately visible, details of curls along the hairline and sectioning of the woman’s hair could be seen in the infrared images. Details of paint application next to the woman’s face are also much more visible in the infrared. I also had the chance to capture ultraviolet images and produce infrared false color images which provide good information on the distribution of certain pigments (including rose madder and Egyptian blue) over the surface.

We look forward to learning more about the Fayoum portrait over the next year and to featuring the results in an upcoming Kelsey exhibition about color in the Roman world. Many thanks to our friends at the Detroit Institute of Arts for their support of this project!

 

Using UV light to examine ancient paint

BY MADELEINE NEIMAN, 2014–2015 Samuel H. Kress Conservation Fellow at the Kelsey Museum. During her time here, Madeleine’s work will focus on the technical analysis and treatment of objects from Seleucia on the Tigris, a site approximately 18 miles south of modern-day Baghdad, Iraq.

One of my major projects here at the Kelsey is conducting a survey of artifacts from the Seleucia collection. The goal of this work is to answer three questions:

  • What are the artifacts made of and how are they made?
  • What is the condition of the object? More simply, is there any evidence of damage or deterioration (e.g., breaks, cracks, discoloration) present?
  • Have the objects been modified (e.g., repaired or reused) in any way by modern or ancient people?

Conservators utilize a number of tools to help us answer these questions. Today I thought I would share with you a bit about one of our most commonly employed techniques — examination under ultraviolet light.

Light is a form of electromagnetic radiation and exits as part of a large electromagnetic spectrum. Ultraviolet radiation, often called UV light, refers to that area just below what is visible to the human eye. While we can’t see UV light, when it illuminates the surface of an artifact, certain types of materials, including some dyes, minerals, and resins commonly found on archaeological objects, fluoresce. These materials glow different colors!

Let’s look at an example.

Among the over 13,000 objects in the Seleucia collection are a group of bone figurines.   Several of these are decorated with a reddish-pink paint that displays a unique orangey-pink fluorescence.

Images of bone figurine (16187) with pink paint captured under visible (left) and UV (right) illumination.
Images of bone figurine (KM 16187) with pink paint captured under visible (left) and UV (right) illumination.

In antiquity, people created paints using mineral pigments as well as organic colorants found in plants and animals. Among the most common sources of red were the pigments hematite (iron oxide), cinnabar (mercury sulfide), and red lead as well as the dyes kermes (from the Kermes vermilio insect) and madder (from the plant Rubia tinctorium).  When viewed in visible light all five appear red. However, when examined under UV light, one stands out: madder. Madder contains four principal colorants: alizarin (red), purpurin (red), pseudopurprin (red) and xanthine (yellow). The purpurin and pseudopurpurin glow a bright orangey-pink when exposed to UV light, making it easy to distinguish.

By examining the figurines under UV light we can tell that an ancient artist used madder to decorate these figurines!