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The Science of Conserving
Culture
By Dorothy Wright
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Korean
Archaeological objects, dating to
the Three Kingdoms period (57 BC -
668 AD), from the Smithsonian Institution's
Freer Gallery of Art.
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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
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
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Metropolitan
Museum of Art, Robert Lehman Collection,
1975
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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."
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
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
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.
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