Working diligently to remove a gray salt layer from a million
individual pieces of glass, three Czech conservators and a UCLA
scientist have been restoring a renowned mosaic in central
Europe.
Materials science is forging its way into the future with new
technologies in metallurgy, optics and nanotechnology ““ but
one of its more surprising applications is its recent marriage with
the world of medieval art.
UCLA Professor Eric Bescher has been traveling to Prague for a
decade now, applying a material he and his colleagues created to a
mosaic titled “The Last Judgment.” The application of
the substance, called sol-gel, is meant to prevent weather
corrosion that could cause the pieces to be obscured forever.
Bescher traveled to Prague for annual maintenance last week and
will be returning again in the next month.
The materials science professor returns to the Czech capital
every year to remove and reapply the top coating so that the
sol-gel remains effective in battling atmospheric corrosion.
Sol-gel is often used as a protective coating, as an outer layer
on sunglasses or on aircraft windows, but the UCLA team’s
application of sol-gel to art conservation is unprecedented.
“Sol-gel has been proposed as an alternative conservation
treatment for corrosion, but its not been used to the extent that
we have used it,” Bescher said.
“The Last Judgment” spans 10 meters by 13 meters
above the south entrance of the St. Vitus Cathedral, which resides
inside the sprawling grounds of the Prague Castle in the Czech
Republic.
The mosaic is composed of three panels. The central panel
depicts Jesus Christ surrounded by angels gazing down at Czech
patron saints and the royal family.
The two side panels depict scenes from heaven and hell.
“The mosaic has a huge symbolic significance in the Czech
Republic. It is located right in the center of power. … It is a
huge work of art, not just physically, but also
symbolically,” Bescher said.
Czech conservators have been attempting to conserve the mosaic
with organic polymers, the building blocks of synthetics, since the
1950s, but these materials could not withstand ultraviolet
radiation and gases from the atmosphere, Bescher said.
The Getty Conservation Institute contacted Bescher and retired
professor John Mackenzie of the materials science department at the
Henry Samueli School of Engineering and Applied Science at UCLA in
1992 to develop a new material technology to conserve the
14th-century glass mosaic that lay hidden under layers of corrosion
caused by gases in the atmosphere.
“(The Getty Conservation Institute) said they had been all
over the world and nobody was able to put a successful coating on
the glass,” Mackenzie said.
Over the span of three years, Bescher and Mackenzie developed a
successful multi-layer coating composed mostly of sol-gel and
covered with a removable top layer made of a traditional polymer,
and tested it in UCLA labs.
The results were successful and were soon tested at Getty labs
under extreme weather simulations, considering that Prague winters
reach approximately minus 20 degrees Celsius, Bescher said.
Unlike polymers, sol-gel’s ceramic nature allows it to
resist the effects of weather and corrosion more easily, and its
liquid form makes it simple to apply. It has the same consistency
as paint and can be applied with a small brush, Bescher said.
“Sol-gel is a process by which you can make a ceramic at
or near room temperature starting from a liquid, which is different
from the traditional way of making ceramics, which usually involves
firing at very high temperatures” Bescher said.
Working with the Office of the President in the Czech Republic,
in 1998 Bescher began applying the sol-gel to the 1 million
square-inch pieces of glass, called tesserae, that had to be coated
by hand without applying any sol-gel to the material between the
pieces.
The sol-gel layers underneath the top polymer layer are
estimated to last for 25 years. After that time Bescher predicts
that he will need to return to fully remove and reapply all sol-gel
layers.
Besides employing his scientific knowledge of materials, Bescher
said he had to learn about the concerns of art conservators.
“We had to worry about the way the mosaic looked. You
can’t make a mosaic look like it was just made yesterday; you
have to make it look like it is 700 years old,” Bescher
said.
The mosaic was also originally gilded; therefore, Bescher and
the Czech conservators had to carefully insert tiny pieces of gold
foil into each tesserae, according to the Prague Castle Web
site.
All three panels have been finished, and the mosaic was reopened
to the public in 2003.
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