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Preservation: The Sciences in Art and Art History

On Feb. 23, United States Library of Congress preservation research scientist Lynn Brostoff presented her studies of ancient artifacts and works of art using scientific methods in her lecture “Using Science to Unlock the Secrets of Art and Historic Artifacts” as part of the Natural Science and Mathematics Colloquium series.

Given in the Schaefer Hall lecture room, Brostoff’s lecture focused on her role in the field of cultural heritage science, which includes elements of biology, chemistry, physics, forensics, and materials science (the analysis of how an object’s properties are linked to its atomic and molecular structure).

“We’re doing a lot of material science,” said Brostoff, “and what the materials present say about the condition of the object.”

Brostoff discussed how the analytical study of museum and library collections is based on technical studies, model studies of degradation mechanisms, and conservation methods development.

Technical studies refers to the study of a material’s identity, methods of manufacture, the history of the manufacturer, innovations of certain components of the object, and the context of the object in relation to its found location.

“A lot of people develop analytical tools specifically for the applications we have,” she said.  “The first thing we want to do is look at things non-invasively.”

Electromagnetic (EM) radiation is the primary method that scientists like Brostoff use to analyze artifacts non-invasively.

The EM waves are scattered, reflected, transmitted, and absorbed by different objects, the results of which are detected and analyzed to understand more about the artifacts in question.

Microscopy, spectral imaging, and Raman spectroscopy are other methods of analyzing these materials.

When more analytical techniques are needed, the next stage of object investigation is the use of minimally invasive techniques, which includes calorimetry and even fold endurance testing on micro-samples of the object.

Brostoff discussed examples of several artifacts analyzed by the preservation staff of the Library of Congress, including a fifteenth century version of the Armenian Gospel from Verin Noravank Monastery in Siwnik (Syunik Province), Armenia.

The book itself was acquired by the Library of Congress in 2008, and has since been under intensive technical study.

The objective of working with the book is to preserve the colors and text of the Gospel of St. Mark, which is inside the book.

Beginning with X-ray fluorescence, or the use of X-rays to excite electrons of atoms on the surface enough to cause a detectable energy release, Brostoff explained how the artifact was analyzed in terms of the colors used on one of the pages.

The X-ray fluorescence, or XRF, detected tin oxide in the work, a rare white pigment that was used to make the white color used on the pages.

XRF also detected smalt (a cobalt glass material from arsenic ore) used for the blue in the book’s pages.  This finding was especially surprising, as it was thought that smalt was not used until Venetian paintings over a century later.

Further analysis of the blue pigments on the page with Fourier transfer infrared spectroscopy (FTIR) indicated the presence of ultramarine, a silicon oxide compound also known as lapis lazuli, found almost exclusively in what is now Afghanistan.

Further cobalt traces indicating smalt presence were verified with elemental analysis.  Doing all of these tests aided in accurate identification of the pigment compounds.

“We could have missed the pigment elements by doing only one analytical technique,” said Brostoff.

The red pigment of the page was analyzed and found to contain mercury and lead, common sources of red in other works at the time.

Further analysis with micro-XRD indicated lead tetroxide for the lead source, and mercury sulfide for the mercury source.

The fact that all of these different compounds could be used for the painting makes more sense given the proximity of Syunik to the Silk Road, the main trade route of the time.

The Persian influence can even be seen in the pages’ artwork.

“There is little known about Armenian painting,” said Brostoff, “so this told us a lot.”

Another method of analysis used by the lab is laser ablation inductively-coupled mass spectrometry (LA-ICP-MS), which was used to analyze trace elements of Ancient Chinese gold.

XRF was also used to analyze the moon dust left on the space suits of astronauts from the Apollo 17 mission.

“You can never see with the naked eye where we’ve been,” said Brostoff.  “And digitizing does not replace study and analysis.”

“I thought the lecture was interesting,” said Kevin Tennyson, a first-year Physics student who attended the talk.

“I have an appreciation for the physics of it, and the materials science that I personally would not have thought of.”

 

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