Greek Scientists use lasers to clean the Acropolis

Standing on a hilltop at the center 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 colors 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 gray one. The new system blasts off layers of black film leaving the marble details intact, without discoloration.