Treatment
 

Once a method for the removal of the corrosion was identified and a system for the protection of the mosaic glass was developed, the conservation plan was nearly ready to be implemented. To complete the development of the conservation plan, the difficult question of regilding had to be addressed. A panel of international and Czech art historians, conservators, and experts in ethical issues of conservation met in Prague in 1996 to discuss the ethics of regilding the mosaic. After considering the values of the mosaic and the importance and extent of the original gilding, the committee agreed that the mosaic should be re-gilded.

Treatment of the mosaic was initiated following the completion of other aspects of the project—that is, conservation survey of the mosaic, study of archival materials, scientific investigation of mosaic corrosion, initial studies in organic coatings, subsequent studies of sol-gel coating technology, and laboratory and in situ testing of sol-gel coatings. Treatment began in 1998. Conservation of the mosaic included cleaning, replacement of missing tesserae, coating, and regilding.

The coating is a multi-layer system. The first layer—the one in direct contact with the glass of the tessera—is a sol-gel layer (an organic inorganic hybrid). The organic portion of this sol-gel layer allows the adhesion to the next layer. The material in this layer is combined with a cross-linking agent to produce a stable material, which, when necessary, was used for embedding gold leaf. Without the cross-linking agent, the same material has greater solubility and was used as a sacrificial layer.

In the application process, all layers were heat-treated using computer-controlled banks of infrared lamps. The top layer is a "sacrificial layer" that protects the underlying layers and will be replaced during scheduled periodic maintenance of the mosaic. The coating is designed to protect the mosaic surface for a long period, but is reversible and can be removed if and whenever necessary.

Work Completed

  • Conservation of the central panel of the mosaic (1998).
  • Conservation of the right panel of the mosaic (1999).
  • Conservation of the left panel of the mosaic.
  • Completion of graphic conservation documentation.
  • Development of a monitoring and maintenance plan for the mosaic (short-term maintenance will occur every five years, and long-term maintenance, with replacement of the protective coating system, every twenty to twenty-five years).

Last updated: December 2009