Greek scientists use lasers to clean Acropolis
In the past two and a half thousand years, the temples of the
Acropolis have suffered fire, bombing and earthquake. Now, scientists
are trying to save them from a new modern enemy: pollution.
Standing on a hilltop at the centre of Athens, a city of 4 million
people, the Acropolis’ elaborately sculptured stones have fallen prey to
a film of black crust from car exhaust fumes, industrial pollution, acid
rain and fires.
A team of Greek engineers and restorers are using an innovative laser
technology system to clean the surface of the ancient monuments,
uncovering colours and ornamentation hidden for decades.
“It is very serious,” said Maria Ioannidou, director of the Acropolis
Restoration Service, of the pollution.
“It destroys sculptural, structural and painting details. One of our
aims is to regain these cultural details using new technology.”
For years the team tested 40 different methods, including mechanical
and chemical processes, to find the safest solutions to restore the
white of the marbles without losing detail.
The winner was the brainchild of Crete’s Foundation for Research and
Technology, which created a system that uses two laser beams of infrared
and ultraviolet rays simultaneously.
These rays have been used separately to clean ancient marble, but it
was found that one left a yellow tint while the other left a grey one.
The new system blasts off layers of black film leaving the marble
details intact, without discoloration.
But it is a risky process.
“If you remove something you cannot put it back in place, so we must
be quite sure that we remove unwanted pollutants and leave ... all the
information on the original surface,” said Evi Papaconstantinou, the
chemical engineer in charge of the team.
The system was first used on the sculptures of the west frieze of the
Parthenon temple in 2004. Now the team has begun a second operation on
the porch of the Caryatids, where besides pollution they must erase soot
from fires and the mistakes of past restorers who tried to mend the roof
with cement.
Scientists first scan the marbles with ultrasound and an infrared
imaging and spectroscopy system to reveal what lies beneath the black
crust. To their astonishment, they found colours, ornamentation and
script that had been hidden for years.
Even wearing goggles, restorers can work only for two hours a day
because of the flashing rays from the laser.
They lie on a reclining doctor’s chair to carry out the time
consuming process on the roof inch by inch.
Restoring the Caryatid porch is expected to take one year, but the
cleaning will continue as long as pollution persists.
“The conservation team will remain on the rock because the marble is
alive. It will remain exposed to the atmosphere,” said Papaconstantinou.
For years, archaeologists and scientists have debated how to protect
the monuments from pollution, some even suggesting the temples be
covered with domes. The creation of an Athens subway helped reduce
pollution, but vehicles still cram the streets and the Greek capital
remains blanketed in a thick smog.
Acid rain has eroded some fine details from the porous marble of the
Acropolis sculptures, including the Caryatids, and have had to be moved
to museums and replaced with replicas.
“We can’t stop the pollution, but we can lessen the effects,” said
Ioannidou.
REUTERS
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