The ancient ruins of the High City in Athens are covered with soot, dirt, random metals, and crumbling cement from sloppy early restorations. Plus, acid rain and pollution have left many of the Sacred Rock's monuments deteriorated and forlorn. In attempt to restore the original marble, the Acropolis Restoration Service explored 40 different ways to clean these centuries-old buildings without damaging any of the intricate details that remain. They finally settled on the coolest and most futuristic-sounding idea — zapping away the black debris with ultraviolet and infrared lasers.Cleaning the monuments of ancient Greece is not as simple as a sandblast. There are layers of black soot deposits that must be destroyed, yes, but there's also the orange-brown "patina" layer (common on many Greek monuments), a layer of gypsum, and a coating of calcium carbonate, all of which include original tooling traces that the Acropolis Restoration Service wants to preserve. And the black soot crust has different chemical components of varying tenacity and thickness, which means one size doesn't fit all when it comes to scrubbing these buildings.
That is, until scientists at Crete's Foundation for Research & Technology hit upon the idea of laser cleaning. From 2002 to 2005, technicians blasted the West Frieze of the Parthenon with lasers in both the ultraviolet and infrared spectrums. They controlled the wavelength, the energy density, and the number of pulses of the laser used in each region, making sure that they cleaned off only the black soot deposits and left the original structural details intact. Using combined infrared and ultraviolet lasers, they could also correct any discoloration that appeared in the marble as a result of earlier cleaning. It was a slow job, too; workers could only use the lasers for 2 hours a day before eye strain became a serious issue. These new photos from Reuters show the beginning of the next step of the process: the application of this laser cleaning technology to the Porch of the Maidens at the temple Erechtheum. The Acropolis Restoration Service expects to finish this job in about a year. Images from Reuters. Greek scientists use lasers to clean Acropolis [Reuters] The Cleaning of the Parthenon West Frieze by Means of Combined IR- and UV- Radiation [SpringerLink]