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Artful Engineer


By David Greenwald

Published Oct 1, 2006 8:00 AM

If you travel from L.A. 5,960 miles north-northwest, you will arrive in the Czech capital city of Prague, where you will find, within the courtyard of Prague Castle, the cathedral of St. Vitus. There, above the three Gothic arches of the south entrance known as the Golden Gate, you will see The Last Judgment, a 14th-century mosaic of brilliantly colored glass tesserae, tiny pebbles and gold leaf that is the largest and most important artwork of its kind north of the Alps.

Until recently, however, it wasn't so glorious. The reason it is today is because of the work of a UCLA materials science professor and his partnership with the Getty Conservation Institute. For centuries, corrosion had obscured the more than 1 million colored tiles and gilt under an opaque, white-gray layer of decay. Most visitors were not even aware of the 904-square-foot triptych of Jesus Christ, heaven and hell 18 feet above their heads. Earlier restoration attempts — the first was in the 15th century — didn't work. Shortly after each cleaning and preservation, the mosaic would return to its previous grungy state.

Enter Eric Bescher M.S. '89, Ph.D. '97, professor of materials science in the UCLA Henry Samueli School of Engineering and Applied Science. In the early '90s, the Getty Conservation Institute began working with Czech conservators to figure out why the mosaic resisted all attempts to keep it from deteriorating and come up with a way to preserve it. The institute reached out to Bescher, an expert in the science of solgels, a process of creating materials such as glass and ceramic from liquids at very low temperatures, and asked him to devise a coating to ward off corrosion and preserve the glass tiles.

Materials Science Professor Eric Bescher carefully wields a cotton swab to remove the old polymer layer on top of the solgel protecting the 14th-century mosaic known as The Last Judgment in the courtyard of Prague Castle.

Bescher's charge was to create a coating that was flexible, as the mosaic breathes, expanding and contracting with temperature changes. Another requirement was that it be reversible to allow the coating to be removed if it didn't work well. And yet another requirement was that the coating couldn't make the mosaic appear new. "We had to figure out how to restore something, yet make it retain some patina of age," he recalls.

Over a period of several years, Bescher and retired Materials Science Professor John Mackenzie tested hundreds of formulations in the laboratory and shuttled back and forth between Los Angeles and Prague to try out promising samples on the mosaic itself. Finally, the scientists hit upon the solution: a multilayer coating composed mostly of solgel and covered with a removable top layer made of a traditional polymer.

Although the initial restoration was completed in 2000, the top coat needs to be stripped and reapplied every five years, and the entire coating will be redone every 20 to 25 years. That means Bescher's L.A.-Prague shuttle science will continue. He most recently traveled to Prague in the summer to inspect the mosaic and his coating.



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