January 2003

The Science of Conserving Culture

The Gateway Hypothesis of Substance Abuse

Combining the Liberal Arts, Medicine and Business

Confronting Famine Abroad and Obesity at Home

Integrating Teaching and Research in Mathematics

Challenging a Prominent Hypothesis

S&T Briefs

Download PDF

Back to S&T Home

KEEP US INFORMED:
Please send us your comments on this issue, ideas for future issues, and news about your professional interests and accomplishments.

Al Dorof, Editor
adorof@brynmawr.edu
info@brynmawr.edu

© 2003

 

Bryn Mawr College
A newsletter on research, teaching, management, policy making and leadership in Science and Technology

The Science of Conserving Culture
By Dorothy Wright

Korean Archaeological objects, dating to the Three Kingdoms period (57 BC - 668 AD), from the Smithsonian Institution's Freer Gallery of Art.

An early Chinese pectoral consisting of 10 jades attached to a gold chain has been an important object in the collection of the Smithsonian Institution’s Freer Gallery of Art since 1930. A few years ago, the curator of Chinese art learned that similar finds in Eastern Zhou tombs indicated that jades typically were strung on silk cords, not chains. The curator asked Janet Snyder Douglas, M.A. ’80, a conservation scientist in the Department of Conservation and Scientific Research at the Freer and Sackler Galleries, to examine the jades and chain for authenticity and to determine whether their configuration was correct.

Douglas studied the jades using X-ray fluorescence spectroscopy (XRF) and other technologies, and confirmed that the jades were similar in composition and workmanship to those from other Eastern Zhou sites. The chain was also found to be authentic. However, some of the links had been removed from the chain and used to attach the jades in an apparent effort to increase the object’s value to collectors. This important object was found to be a fairly recent pastiche of authentic jades on an authentic gold chain.

Conservation scientists are using sophisticated scientific techniques to determine the age, authenticity and provenance of various cultural treasures — including fine arts, archaeological, architectural, ethnographic and natural history materials. Conservators are also applying their knowledge of science and technology to preserve these treasures for current and future generations to study and enjoy.

A century ago, conservation scientists’ tools were largely limited to visual inspections and simple chemical analyses. Today, a wide range of sophisticated equipment is at their disposal, ranging from atomic absorption spectrophotometry to X-ray diffraction.

Noninvasive Techniques

Janet Douglas,
M.A. ’80

Many of the scientific techniques used today to examine art and antiquities are noninvasive or require minimal sampling in order to protect these valuable materials. At the Freer and Sackler Galleries, Douglas uses nondestructive scientific methods to examine Asian works of art and related materials, including jade, stone, pigments, paper and metals. She is a pioneer in the use of XRF to study the chemical composition of Chinese nephrite jades dating from the Neolithic period to the Han dynasty.

Douglas uses a customized Spectrace Model 6000 XRF, called an Omega 5, which was acquired by the galleries in 1988. "The instrument is mounted on a turret so that it can be positioned to obtain an analysis directly from the surface of an object in virtually any orientation," she explains. "There were very few XRF instruments being used in museum settings in 1988, and their applications were limited. The Omega 5 gave us the flexibility to look with ease at three-dimensional objects."

The use of modern technology has helped scientists and curators to redefine objects that have been in the collections for many years. Recently Douglas used XRF and scanning electron microscopy to take a fresh look at a group of archaeological Korean beads that has been in the collection since 1917. "Although some of the beads look very much like jade and were identified as such in museum records, we discovered that they are made of early alkali glasses," she says. "Without the technologies we now have at our disposal, many routine materials identifications of this type would be difficult."

The Phantom Bather

Metropolitan Museum of Art, Robert Lehman Collection, 1975

Last spring, as the Metropolitan Museum of Art was preparing a special exhibition on Paul Gauguin, a conservator noticed an unusual surface texture in an oil painting titled "Tahitian Women Bathing." This prompted an examination by Alison Hart Gilchrest ’97, a research associate in the Met’s Paper and Paintings Conservation departments. Using reflectography, a specialized infrared imaging technique, Gilchrest discovered the image of a hidden figure that Gauguin had drawn and painted, but then painted over.

"Surprises on this scale are rare," Gilchrest says, "but when you find them, they are treasures."

Gilchrest says conservation research at the Met is highly collaborative and involves studying a wide range of materials and techniques, as well as their historical contexts. "Before an object is considered for conservation treatment, it is important to understand it as thoroughly as possible," she observes. "Infrared photography or reflectography can reveal carbon-based preparatory drawings beneath the surface of works of art. It's a terrific combination of art and science."

Alison Gilchrest ’97

The technology’s roots go back to the 1930s, when a researcher at Harvard used IR-sensitized film to see beneath the surface of a thickly varnished painting. Reflectography was developed in the 1970s by a Dutch researcher who adapted declassified military imaging equipment to study Flemish primitive paintings. Maryan Ainsworth, a curator at the Met, began to use this technology at the museum in the 1980s.

"Infrared examination might reveal broad compositional changes or an underdrawing that is incongruent with what one might expect to see," Gilchrest says. "The information is useful not only to conservators, but also to curators and art historians who gain better insight into the artist and his working methods."

Conservation Writ Large

Catherine Matsen ’97

Architectural conservation presents large-scale challenges. Take Drayton Hall, a National Trust historic site in Charleston, S.C. Completed in 1742, it is the oldest preserved plantation house in the United States that is open to the public. It has remained in nearly original condition through seven generations of family ownership but, in some areas, century-old paint is deteriorating. As an intern at Drayton Hall in 2001, Catherine Matsen ’97 painstakingly applied an ultrasonic mist of Aquasol, a polymer consolidant, and used a tacking iron to press down peeling paint on test patches.

"Aquasol had been used in fine art conservation since the 1980s, but it had never before been used in an architectural application," explains Matsen, who is in her second year of the University of Pennsylvania's graduate program in historic preservation. "One problem in architectural preservation is how to apply these methods on a large scale. The conservators’ plan was to monitor these test patches over time to gauge the treatment’s effectiveness. Their biggest concern was that it would affect the gloss or color of the paint."

Matsen says strength and gloss tests and cross-section microscopy have shown that the treatment applied in 2001 is achieving conservation goals without altering the paint’s appearance. Although microscopic and chemical analyses are the primary methods used to study paints and other building materials, more advanced technologies — such as XRF and Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and gas chromatography mass spectrometry — also are used to study these materials.

"With the use of modern scientific methods, conservators can be more confident that treatments will not damage the material," says Matsen, who plans to specialize in paint analysis.

Architectural preservation theory dates back to the 19th century, when two prominent theorists, Violet LeDuc and John Ruskin, debated whether buildings should display their age (Ruskin) or be preserved in a pristine condition (LeDuc).

"Early preservation efforts were well intentioned, but damaging," Matsen says. "For example, iron or steel rods sometimes were used to secure masonry ornamentation on buildings. Inevitably, water intrusion caused rusting and further deterioration."

Art conservation treatments were applied to architectural treasures without knowing how these treatments should be adapted for buildings and other structures. "Preservation methods must be based on the unique characteristics of architecture, such as its scale and, often, building codes," Matsen says.

Conserving Special Materials

In 1994, Helen I. Alten ’82 received a call from an archaeologist who had discovered an ancient basket at a wet excavation site and needed to know how best to remove it. Alten, who at that time was state conservator for the Alaska State Museums in Juneau, sent him information on block lifting. Alten excavated the fragile basket in her laboratory with tweezers, fine brushes and an eyedropper. After the basket was donated to the museums, carbon dating revealed that it was some 5,000 years old.

To protect this ethnographic treasure, Alten tried various drying methods on tiny samples of the basket. However, these methods turned the samples to dust or otherwise hindered the ability to study it. Deciding instead to stabilize the basket for later examination, Alten transferred the basket to a small, custom-built Plexiglas tray in a solution of distilled water and alcohol, and placed it in an old four-sided glass Coca-Cola refrigerator, where it could be safely displayed and analyzed.

Relatively few archaeological and ethnographic materials make it that far. Many of these materials are organic — fur, leather, textiles or wood — that have been buried underground, under water or in caves, for example. When removed from these sites, exposure to air, humidity or light can degrade or otherwise compromise the specimens. "Most archaeologists, especially those in the United States, excavate without the assistance of professional conservators with the training and expertise required to handle these specimens appropriately," says Alten, who is now conservator and president of the Northern States Conservation Center in St. Paul, Minn. "They may do ‘cookbook’ conservation, without much success."

Alten focuses much of her efforts today on ethnographic, natural history and historical objects, carefully designing treatments to stabilize and preserve specimens without harming them. Modern water-soluble waxes, acrylics and polymers contribute to this effort.

"Sometimes it is necessary to intrude on an object in order to preserve it for a few more years," Alten observes. "However, introducing adhesives, consolidants, stitches and fills add another item that may degrade within the object. Slowly conservators are learning that the best approach is the non-intrusive approach."

Preventive Conservation

Catherine Sease ’69

In 1987, Catherine Sease ’69 published A Conservation Manual for the Field Archaeologist. Now in its third edition, the manual has become a standard guide on field treatment techniques for archaeologists and conservators.

Sease, senior conservator at the Peabody Museum of Natural History at Yale University, is as concerned today about museum climate control as she is about proper field treatment. "Uncontrolled humidity is the greatest long-term problem in archaeological conservation," she explains. "Yet most museums do not have climate-control systems in place."

For example, Egyptian ceramics in the Peabody’s collection are suffering the effects of water-soluble salts that migrated into the pieces when they were buried in the ground. "Humidity fluctuations cause the salts to go into solution and migrate to the surface of the piece, where they crystallize, and then go back into solution," she explains. "Over time, the piece disintegrates. You have two choices: control the humidity or treat the effects."

Climate control is not a simple matter of installing air conditioning and dehumidifiers. "We have to achieve very strict standards, which are far beyond the capability of standard air-conditioning systems," Sease says. "Most museums don’t have the money for that."

The Peabody recently completed a new wing, much of which is dedicated to collection storage under sophisticated climate controls. "So now we need to push for the collections that didn’t get into this building — the anthropology, archaeology and invertebrate paleontology collections," Sease says. "Conservation has changed its focus over the last 20 years from actively treating objects to practicing preventive conservation. It is very rewarding to help preserve our heritage, knowing it will be there for future generations to appreciate and study. It is all a part of the human story."

About Our Sources

Helen I. Alten ’82 is conservator and president of the Northern States Conservation Center in St. Paul, Minn. An archaeology major at Bryn Mawr, she received a B.Sc. degree in conservation from the Institute of Archaeology, University College, London. As conservator for the Montana Historical Society, Alten built its conservation laboratory and prepared 3,000 objects for its permanent Centennial exhibit, Montana Homeland. She joined the Alaska State Museums as state conservator, providing conservation services to museums throughout the state. Alten has served as an archaeological conservator on excavation sites in Alaska, Bulgaria, England, Greece, Israel and Italy.

Janet Snyder Douglas, M.A. ’80 (geology), is a conservation scientist in the Department of Conservation and Scientific Research at the Smithsonian Institution’s Freer Gallery of Art and Arthur M. Sackler Gallery. She has a B.S. degree in geology from James Madison University. Prior to joining the Smithsonian, Douglas was a geologist in the Particulate Mineralogy Unit of Avondale Research Center of the Bureau of Mines, U.S. Department of the Interior, where she characterized mineral dusts related to health and safety issues in the mining industry.

Alison Hart Gilchrest ’97 is a research associate in the Paper and Paintings Conservation departments of the Metropolitan Museum of Art. As a history of art major at Bryn Mawr, Gilchrest interned at the Philadelphia Museum of Art, where she conducted an independent study of infrared examination. She has an M.S.I.S. degree from the University of North Carolina.

Catherine Ruth Matsen ’97 is in the second year of University of Pennsylvania’s graduate program in historic preservation, planning to specialize in paint analysis. After graduating with an A.B. degree in chemistry, she worked as a lab technician for the DuPont Company. Matsen then joined Winterthur Museum as a laboratory analyst in the Conservation Department. She has interned at Drayton Hall, a National Trust site in Charleston, S.C., and the Architectural Research Department at Colonial Williamsburg.

Catherine Sease ’69 is senior conservator at the Peabody Museum, Yale University. An anthropology major at Bryn Mawr, she received a B.Sc. degree in conservation from the Institute of Archaeology, University College, London, where she also taught in the Conservation Department. Sease then joined the Objects Conservation Department at the Metropolitan Museum of Art, where she was the head conservator for the installation of the Rockefeller Wing of Primitive Art. She worked privately in New York before joining the staff of the Anthropology Department at the Field Museum of Natural History, Chicago, where she was head of the Division of Conservation. Sease has worked on numerous excavations in Britain, Greece and the Middle East.

About the Author

Dorothy Wright contributes news and feature articles on science, technology, engineering and general interest topics to a variety of publications, including Civil Engineering, Engineering News Record and Bryn Mawr Now.

Back to Top