A condition survey in 2004 showed that close to half of the ceramics in the Museum's Late Archaic and Early Classical Greek gallery were physically unstable. Many of the ceramics, assembled from fragments, were heavily restored before they came to the Museum in the late nineteenth and early twentieth centuries. After more than a century, they were in dire need of conservation. All of the vessels required cleaning and many were plagued with failed adhesives, soluble salts, and discolored restoration paints.
The retreatment of forty-five of these ceramics, funded by the Leon Levy Foundation, requires, in most cases, complete disassembly, desalination, removal of old restoration materials, filling in gaps, and inpainting. The project's goals include not only the stabilization of these vessels, but also the improvement of their appearance, making them comprehensible to art connoisseurs, academics, and the general public.
See photos of vessels before, during, and after conservation.
In addition to the conservation treatment of the vessels, the grant from the Leon Levy Foundation enables an investigation into salt contamination as well as the identification of earlier restoration materials found on this important collection of ceramics.
Soluble Salt Contamination
It is not unusual that soluble salts, such as nitrates, sulphates, and chlorides, are deposited in a ceramic body by groundwater during burial; obsolete restoration practices; or the off-gassing of harmful materials, such as those found in some storage cabinets or even other artifacts. Once trapped in the ceramic body, these salts are subject to cycles of crystallizing and dissolving as the humidity rises and falls. The crystallization of the salts, which occurs at and just under the surface of the ceramic, can exert enough pressure to cause delamination or surface loss.
Determining whether or not a ceramic vessel is afflicted by salts is not always easy. The accuracy of different techniques used to identify salts is being evaluated and compared. It is expected that findings will help conservators in setting treatment priorities within large collections of restored, archaeological ceramics.
Samples of materials used in previous restorations are being identified by the Museum's Scientific Research Department using Fourier Transform Infrared Spectrometry (FT-IR) and Scanning Electron Microscopy (SEM)/ microprobe analysis. As expected, analysis to date show that most of the vessels were restored using shellac, protein glues, oil paints, gypsum, plaster of Paris, barium sulphate, calcite, clay, and kaolin. However, unusual materials such as waterglass (calcium silicate) have also been identified.
While all or most of these materials were typically used in the nineteenth and early twentieth centuries, it is hoped that information regarding specific materials used in tandem with unusual practices (for example, using printed sheets torn from auction catalogues to back plaster fills), will be useful in identifying groups of vessels coming from particular restoration studios or collections.
Generous support for this project provided by the Leon Levy Foundation.