Foto: John Kolesidis/Reuters. En los últimos 2.500 años, los templos de la Acrópolis sufrieron el fuego, las bombas y terremotos. Ahora, los científicos intentan salvarlos de un nuevo y moderno enemigo: la polución.

Edificada sobre una colina en el centro de Atenas, una ciudad de unos 4 millones de habitantes, la Acrópolis ha caído presa de una fina capa de costra negra a causa de los gases de los automóviles, la polución industrial, lluvia ácida e incendios.

Vía: Deborah Kyvrikosaios, ATENAS (Reuters), domingo 26 de octubre de 2008 07:20 GYT

Un grupo de ingenieros griegos y restauradores están utilizando un nuevo e innovador sistema láser para limpiar la superficie de antiguos monumentos, descubriendo colores y decoraciones escondidos por décadas.

"Es muy serio", dijo Maria Ioannidou, directora del Servicio de Restauración de la Acrópolis, sobre la polución. "Destruye detalles esculturales, estructurales y en las pinturas. Uno de nuestros principales objetivos es recuperar estos detalles utilizando nueva tecnología", añadió.

Durante años, el equipo probó 40 métodos diferentes, incluidos procesos mecánicos y químicos, para hallar la solución más segura para restaurar el blanco de los mármoles sin perder detalles.

El ganador fue la creación de la Fundación de Estudio y Tecnología de Creta, que elaboró un sistema que utiliza dos rayos láser infrarrojo y ultravioleta simultáneamente.

Foto: A restorer cleans decorations on the wall of the porch of the Caryatids of the Erectheion temple on the Acropolis in Athens, October 16, 2008, after laser beams were used to remove a film of black crust caused by pollution. A team of Greek engineers and restorers are using the innovative laser technology system to clean the surface of the ancient monuments, uncovering colours and ornamentation hidden for decades. Picture taken October 16, 2008. John Kolesidis/Reuters.

Estos rayos se habían utilizado separadamente para limpiar el antiguo mármol, pero uno dejaba un matiz amarillo mientras el otro uno gris. El nuevo sistema destruye las capas de polvo negro dejando intacto los detalles del mármol, sin decolorarlos.

Pero es un proceso riesgoso.

"Si se remueve algo, no se puede volver a colocar por lo que debemos estar absolutamente seguros de remover contaminantes y dejar toda la información en la superficie original", dijo Evi Papaconstantinou, ingeniero químico a cargo del equipo.

El sistema fue utilizado primero en las esculturas del friso oeste del Partenón en 2004. Ahora, el equipo comenzó una segunda operación en la galería de las Cariátides, donde además de la polución los científicos deben eliminar el hollín de los incendios y los errores de restauradores pasados que intentaron arreglar el techo con cemento.

Los científicos primero escanean el mármol con ultrasonido y un sistema infrarrojo y de espectroscopia para revelar lo que se halla debajo de la costra negra. Para su asombro, encontraron colores, ornamentación y caligrafía que había estado escondida por años.

Incluso usando lentes de protección, los restauradores pueden trabajar sólo por dos horas diarias debido a los rayos del láser. Realizan el consumidor proceso en el techo milímetro por milímetro sentados en una silla reclinable.

La restauración de la galería podría llevar hasta un año, pero la limpieza continuará mientras persista la contaminación.

"El equipo de conservación permanecerá en el lugar porque el mármol está vivo. Continuará expuesto a la atmósfera", dijo Papaconstantinou.

Durante años, arqueólogos y científicos han debatido cómo proteger los monumentos de la contaminación, algunos sugirieron que los templos fueran cubiertos con cúpulas.

La creación de un metro en Atenas ayudó a reducir la polución, pero los vehículos aún atiborran las calles y la capital griega sigue siendo invadida por una capa de esmog.

La luvia ácida erosionó algunos detalles de las esculturas de mármol de la Acrópolis, también en las Cariátides, por lo que debieron ser llevadas a museos y reemplazadas por réplicas.

"No podemos detener la polución, pero podemos reducir los efectos", dijo Ioannidou.

(Editado en español por Patricia Avila) © Thomson Reuters 2008.

Foto: A conservator uses a laser beam to clean grime and soot off a sculpted marble band on the 5th Century B.C. Erechtheion Temple on the Acropolis of Athens on Thursday, Oct. 30, 2008. The relief sculpture, covered with egg-and-dart decoration, belongs to a 60-meter (197-foot) frieze that ran round the temple just below roof level. Greek authorities are engaged in a decades-long operation to conserve the marble monuments on the Acropolis hill, a World Heritage site. (AP Photo/Christos Angelou).

Scientists to measure quake effect on Acropolis

By ELENA BECATOROS, Associated Press Writer Elena Becatoros, Sat Nov 1, 2:02 am ET

ATHENS, Greece – For thousands of years the Acropolis has withstood earthquakes, weathered storms and endured temperature extremes, from scorching summers to winter snow. Now scientists are drawing on the latest technology to install a system that will record just how much nature is affecting the 2,500-year-old site. They hope their findings will help identify areas that could be vulnerable, allowing them to target restoration and maintenance.

Scientists are installing a network of fiber optic sensors and accelerographs — instruments that measure how much movement is generated during a quake.

"The greatest danger for our monuments at the moment is earthquakes," Dimitrios Egglezos, chief civil engineer in charge of the Acropolis' defensive circuit wall, told The Associated Press. So understanding how the structures react to the earth's movement is paramount.

Egglezos said six accelerographs are to be installed starting next week at various parts of the Acropolis: at the base of the hill, part of the way up where the geology changes, and on the Parthenon, the Acropolis' most famous monument, built between 447 and 432 B.C. in honor of the goddess Athena.

"The measurement of earthquakes and their consequences on the monuments is essential," said Maria Ioannidou, who supervises restoration work on the Acropolis.

The fiber optics are installed on parts of the wall to measure subtle changes caused by changing weather conditions or earthquakes, while the accelerographs can help determine how the earth's movement affects the monuments.

"This is the first system that we've installed to record the (natural) activity that affects our monuments," Egglezos said.

They don't look like much: a nondescript small metal box at the foot of a column, barely visible wires snaking across outer walls. But the insight they could give into potential problem areas is invaluable.

The first accelerograph was placed on the hill about two years ago as a pilot program. Another two were installed in late September on the Parthenon, one at its base and one on the top of the columns on the architrave, as part of a study by Japan's Mie University and the National Technical University of Athens.

Greece is one of the most seismically active countries in the world, and while most of its earthquakes are relatively small and cause little or no damage, some have been fatal. In June, a 6.5 magnitude quake in western Greece killed two people and injured more than 200, while a 5.9 magnitude quake near Athens in 1999 killed 143 people.

Neither seriously damaged the Acropolis.

Indeed, some parts of the ancient citadel have weathered the forces of nature remarkably well. The Parthenon survived virtually intact until the late 17th century, when an Ottoman garrison used it as a gunpowder store; it was targeted by Venetian cannon fire and exploded, damaging parts of the temple.

The accelerographs could also give experts more insight into how the Parthenon has withstood earthquakes so well, Egglezos said.

"The earthquakes that don't cause damage are very useful because we have a natural ... experiment which doesn't destroy the monument but gives us valuable information about how these structures behave."

The two accelerographs funded by Mie University will be in place for three years, while the other seven will remain on the Acropolis permanently, Ioannidou and Egglezos said.

The fiber optic sensors, meanwhile, can detect even minor changes in the structure: slight expansion during hot weather, contraction in the cold of winter, the buildup of pressure from a particularly heavy rainfall. And, of course, shifts caused by earthquakes.

They have been installed on two outer parts of the perimeter wall: the southeast which is the highest and most vulnerable point, and on the north wall which shows evidence of damage, probably from an 18th Century quake.

Egglezos said the experts need about one or two years' worth of data from the fiber optics before they can draw any concrete conclusions.

Copyright © 2008 The Associated Press.

Foto: The ancient Parthenon temple, in the Acropolis hill, is seen in this photo from files taken on Feb. 3, 2004. The Acropolis is among the leading contenders to be the new seven wonders of the world as a massive poll enters its final month with votes already cast by more than 50 million people, organizers say. The seven winners will be announced July 7, 2007 in Lisbon, Portugal. (AP Photo/Petros Giannakouris).