Conservation of the Last Judgment Mosaic, St. Vitus Cathedral, Prague consists of a selection of papers presented at a symposium organized by the Getty Conservation Institute and the Office of the President of the Czech Republic. The theme centered on the completion of a twelve-year collaborative project to restore and preserve the Last Judgment mosaic in Prague’s St. Vitus Cathedral.

The volume is divided into three sections:

The first section contains seven chapters describing the art-historical context of the mosaic. In chapter 1, Marie Kostílková analyzes the documentation available on the making and repair of the mosaic between 1370 and 1910. In chapter 2, Zdeňka Hledíková discusses Italian stylistic influences and the role played by King Charles IV in the choice of the general iconographic themes. Zuzana Všetečková in chapter 3 analyzes in greater depth the symbolic meaning of the iconographic representations, particularly the Last Judgment as an allegory of King Charles IV’s own power to exercise on his subjects his earthly judgment. In chapter 4, Carlo Bertelli looks at the technical similarities between the St. Vitus work and contemporary Italian mosaics, referencing the more innovative aspects of the Prague mosaic. Eliška Fučiková in chapter 5 outlines the history of conservation interventions between 1910 and 1992; and Alois Martan in chapter 6 goes into more detail regarding the causes of deterioration and the different remedial techniques of conservation considered at the time, as well as the treatments applied to the mosaic between 1956 and 1992. The last chapter of this section, written by Jan Bonĕk, recounts the search between 1993 and 1995 for any visual records; the result is a gathering of almost one hundred different visual aspects from thirty different collections, thus allowing the detailed reconstitution of the history of the mosaic.

Chapter 8 introduces the second part of the book, dedicated to conservation planning and methodology. Francesca Piqué describes the ethical and technical issues related to the St. Vitus mosaic. She details the ways in which both the assessment of the cultural values linked to it as well as the analysis of its physical condition were essential to solving preventive and remedial conservation issues. In chapter 9, Marco Verità discusses Italian glass mosaic technology in the thirteenth and fourteenth centuries. In chapter 10, Dusan Stulik describes the analytical research conducted on mortar samples and on both old and new mosaic glass. The samples and cross-sections should provide a basic reference compilation for future research into medieval glass and glass technology. Shin Maekawa describes in chapter 11 the environmental issues linked to the preservation of the mosaic in situ. He first describes the monitoring weather station put in place for a whole year and the type of instruments with which it was equipped. He then analyses the data obtained from the microclimate related mainly to air temperature, relative humidity, solar radiation, wind speed and direction, and surface temperature. The results allowed the reproduction and simulation of the same test conditions in a laboratory in order to test potential protective coating materials for the mosaic.

The most striking aspect of the St. Vitus mosaic is the discoloration and obstruction of the design due to surface corrosion. An entire chapter (12), written by Milena Nečásková, is dedicated to the topic of methodology and research into its cleaning. Different cleaning techniques traditionally used on mosaics and glass windows are described, and their suitability for the treatment of the St. Vitus example is analyzed. The air abrasive method was thought to be the most suitable as it restored the original color of the glass and allowed for the application of an organic protective coating.

Because the problem of protective coating is of prime importance for mosaic conservation in general, all of chapter 13 is dedicated to the development of coating technologies. The technology of new sol-gel coatings is introduced, as its combination with an organic fluoropolymer coating seemed the most promising solution for the treatment of the mosaic surface. Four years of laboratory and on-site testing are described, including application techniques. The results, according to the authors (Eric Bescher and John Mackenzie), are very promising in terms of stability. However, they stress the importance of regular maintenance, which, as they say, “has been built into the design of the coating” and is an intrinsic element of its performance “that must not be overlooked” (187).

The third and final section of the volume covers the last three chapters, which are dedicated to conservation implementation and maintenance.

In chapter 14, Nečásková and Piqué discuss the importance of three different types of documentation. First, they describe historical documentation comprising the collection of visual and written information on the history of the mosaic. Second, treatment documentation relating to the recording of the condition of the mosaic before, during, and after conservation intervention is discussed. Third, they list technical documentation related to the technology used to make the mosaic (type of glass, mortars, stratigraphy, etc.) and to the recording of physical evidence of previous interventions. Written, graphic, and photographic records were prepared and made available in digital form. In chapter 15, Nečásková describes the development and implementation of interventions on the mosaic. All the various steps are detailed. This includes the preparatory work and the different stages of the conservation treatment. Also detailed are the application of the protective coating and, finally, the gilding of the background. In the final chapter, Martin Martan, Piqué, and Stulik discuss the highly important issue of monitoring and maintenance. The authors have implemented a monitoring protocol for the early detection of changes in the appearance of the mosaic. This is based on regular visual inspection as well as digital photography. Different cycles are planned for short, medium, and long-term maintenance programs entailing distinct levels of intervention. Two teams have been created consisting of specially trained conservators who have worked on the mosaic and can intervene swiftly when necessary and handle the monitoring and maintenance.

Conservation of the Last Judgment Mosaic, St. Vitus Cathedral, Prague contains color illustrations throughout and is a very good example of the successful collaborative work between scientists and conservators. Rarely do we have the opportunity to read detailed information on different aspects of a conservation project (historical, art historical, technical, scientific, etc.) in one single publication, and this volume offers a particularly comprehensive version.