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!

News from the Conservation Lab

The Kelsey Conservation Lab is pleased to welcome Madeleine Neiman as our new Samuel H. Kress Fellow for the 2014–2015 academic year.

Madeleine is a recent graduate of the UCLA/Getty Program on the Conservation of Archaeological and Ethnographic Materials, and has an undergraduate degree in anthropology from Bryn Mawr College. She just completed a year-long graduate practicum internship at the Arizona State Museum (University of Arizona) and has also previously worked at the Colonial Williamsburg Foundation, the Alaska State Museum, and the Anchorage Museum, where she focused on the conservation and technical analysis of ethnographic and archaeological materials.

Madeleine Neiman
Madeleine Neiman

At the Kelsey, Madeleine’s research will center on conservation projects for the Seleucia collection. For example, she will research and treat an incantation or “demon” bowl from Seleucia, an unglazed ceramic bowl painted with magical spells designed to entrap demons. The inscriptions on this bowl are obscured by a darkened surface layer (possibly a modern coating) and by the presence of chunky salts, probably deposited while the bowl was buried. Important goals of conservation treatment will be to stabilize the bowl’s inscription and make it more legible.

In addition to the bowl, Madeleine will survey and study a group of bone figurines from Seleucia. The figurines are carved in both stylized and naturalistic human forms, and some are painted. Madeleine will collaborate with zooarchaeologist Dr. Richard Redding, as well as materials scientists at U-M and elsewhere, to answer a variety of research questions about the figurines.

Bone figurine from Seleucia
Bone figurine from Seleucia.

We are thrilled to have Madeleine here to research and treat these unique artifacts, and we’re grateful to the Samuel H. Kress Foundation and the Foundation of the American Institute for Conservation for supporting her fellowship. Welcome, Madeleine!

Conservation for Seleucia Show, Part 2

BY BRITTANY DOLPH, Graduate Conservation Intern, UCLA/Getty Conservation Program

Last month, I discussed the documentation aspects of conservation, especially as it pertained to our preparation of objects for the exhibition Life in Miniature: Identity and Display at Ancient Seleucia on the Tigris. Often, when time allows, conservation research can contribute technical information about objects, revealing how the artifact was made and even how it was used during its “life.” Furthermore, technical data aid us in making treatment decisions later on. Though we didn’t have the chance to do additional chemical analysis for this particular exhibition, we used different types of imaging techniques to get as much information as possible. And using different kinds of light in different ways for gathering information is ideal because it allows us to avoid taking samples. For example, a visual assessment can reveal seams, showing us that the miniature ceramic figurine below was made in two separate clay pieces before being joined together and fired.

Image
This ceramic figurine, photographed from the rear, shows a seam running along the contour of the left side from bottom to top. Fingerprints are visible along the seam as well, where the maker attempted to bridge the sides by pushing the clay over.

A look through a simple binocular microscope can show tool marks that provide clues to how an object was made. For example, a stone figurine could have been roughly cut to size using a chisel or claw, then carved with final tools, and perhaps filed to create a smoother surface. In other cases, microscopy can reveal the remnants of pigment applied to a surface. In addition, condition problems such as micro-cracks, spots of metal corrosion, and many other issues are identified.

Conservators also often flash ultraviolet irradiation (sometimes incorrectly referred to as light) onto the surface of objects. Different materials react differently to the UV, so that we can often tell where additional materials have been applied by the color, strength, and opacity of their fluorescence or lack thereof. It can be especially helpful for finding previously applied conservation or repair materials.

Visual assessment . . . microscopy . . . UV . . . what do we do with all of this information? It helps to us to make decisions — which, it turns out, is a big part of the job! The first step is to decide whether or not even to treat an object. If we decide that treatment is necessary, we then have to decide how to go about it and what materials to use.

Next month, we’ll take a look at examples of treatments — and situations where we might decide not to treat at all.