An eight-year international collaboration among scientists, art historians, and conservators culminated in Prague on September 15, 2000, with the unveiling of The Last Judgment, a 14th-century glass mosaic that is one of the Czech Republic's most significant cultural treasures. Czech President Vaclav Havel joined senior Getty staff at St. Vitus Cathedral for the first public presentation of the mosaic following completion of the conservation work that was undertaken by the GCI and the Office of the President of the Czech Republic.

The Last Judgment, the earliest and most important monumental exterior medieval mosaic north of the Alps, covers 84 square meters (904 square feet) of the cathedral's south facade. Since its creation in 1371, the glass mosaic has rarely been seen in its full splendor. It has faced repeated threats from wars to fires—and, more recently, environmental pollutants.

Divided by Gothic spires into three sections, The Last Judgment depicts Christ surrounded by angels in the central panel, and scenes of heaven and of hell in the two side panels. The brilliantly colored mosaic comprises more than a million small glass tiles and stone pebbles, in more than 30 different hues. Until now, conservators have been unable to prevent the recurrence of a grayish layer of corrosion that obscures the mosaic.

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The current conservation effort required extensive scientific and art-historical research and the development of new conservation methods and materials. In the process, vital international exchange was facilitated. The challenge was not merely to clean the fragile mosaic but to ensure its future survival by coming up with a coating that would stabilize and protect it, preventing further deterioration and allowing it to remain visible.

The project team began by analyzing the mosaic's material and decay products to understand the process of deterioration. Over the course of several years, they then tested numerous approaches to cleaning and protecting the mosaic. Actual treatment of the mosaic got under way two and a half years ago. The central panel was completed in the summer of 1998, the right panel in the summer of 1999, and the final, left panel in the summer of 2000. A team of GCI and Czech conservators cleaned the mosaic using special microsandblasters, and they painstakingly applied a multilayer protective polymer coating adapted from the aerospace and medical industries. This is the first time that the high-tech coating—developed in collaboration with the Department of Materials Science Engineering at the University of California, Los Angeles—has been applied for art conservation purposes.

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The project also contributed to major advances in the art historical analysis of The Last Judgment mosaic. Archival holdings related to the mosaic have expanded with the discovery of a number of historical documents and photographs, as well as extensive new documentation. The GCI's own holdings of related material now exceed 5,500 items. Conservators who had worked on earlier restorations of the mosaic, in the 1950s and 1980s, were also brought into the process, giving the project not only a multinational but also a multigenerational character.

The results of the project team's findings will be shared as a service to the field through publications and a symposium in June 2001. Additionally, the team has developed a mosaic maintenance protocol, to be carried out under the supervision of Prague Castle to help ensure the long-term preservation of the conservation work.

In recognition of his substantial contribution to the mosaic's conservation, Dusan Stulik, the mosaic's project manager for the GCI, was awarded the Presidential Medal of the Czech Republic. (Stulik, a GCI senior scientist, is himself a native of Prague.) In addition, the J. Paul Getty Trust and the Getty Conservation Institute were each awarded the Presidential Medal.