Glass Sickness

08Its detection, prevention and treatment.
Guus Verhaar, Conservation Science.

Glass sickness is a form of deterioration affecting glass of all periods and from all glass-making centres. This research will consider the issues leading to tendency of certain glasses to exhibit glass sickness. Whilst focusing on the detection, research into prevention and treatment will also be part of this research.

BK-NM-804-01The research in this collaborative project between the Amsterdam School for Culture and History at the University of Amsterdam and the Rijksmuseum conservation department, tackles the most significant, unsolved problem in the conservation of vessel glass collections: glass ‘sickness’. Glass sickness describes the decay of glass as a result of poor glass manufacturing recipes. As a result of a faulty balance of the three essential components for glass-making, about 10% of museum and other glass collections consist of items which are inherently prone to decay. This process is brought about by atmospheric moisture which induces a slow, irrevocable change in appearance of unstable glasses. The progressive effects of glass sickness are the formation of a moist, ‘weeping’ surface, the development of hairline cracks on the glass surface, and, ultimately, complete cracking and disintegration of susceptible items, known as ‘crizzling’.

FingerprintThe impetus of this proposal was an extensive condition survey of the glass collection of the Rijksmuseum. It became clear that glasses of different origin showed similar degradation patterns, but apparently in a different stage of the degradation process. While on some objects clear signs of chemical degradation were visible, others simply have a dull appearance and it is often unclear whether this is an indication of glass sickness, or an unrelated contamination of the surface. When it transpired that Museum Boijmans van Beuningen was grappling with similar problems, it became clear that gaining more information on these possible signs of glass deterioration is necessary.

Therefore, this PhD project will investigate and develop analytical methods (using, primarily, ion chromatography) of detecting the early stages (i.e. before irreversible changes have occurred) of glass sickness. By pinpointing susceptible glasses, preventive measures can be put in place to stall the progress of glass decay. Recommendations on suitable environmental parameters for display and storage will therefore also be part of the research program. Finally, with a detection methodology and preferred environmental conditions in place, the research will tackle remedial strategies for already crizzled glass. The key approach would be to match the refractive index of the disintegrating glass with suitable consolidants. This approach leads to ‘invisible’ repair of cracked glass but has never been investigated for crizzled glass.

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