Proc. XIX Int. Congr. Glass, Edinburgh, 1–6 July 2001
Glass Technol., 2002, 43C, 364–8
Some observations on crizzled glass (preliminary results of a survey of 18th century central European tableware) J. Kunicki-Goldfinger,1 J. Kierzek & B. Ma¢o¯ewska-Buçko Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw, Poland
A. J. Kasprzak National Museum, al. Jerozolimskie 3, 00-495 Warsaw, Poland
Preliminary results of surveys of 18th century central European colourless tableware have been reported. The survey included an energy dispersive x-ray fluorescence analysis and a visual inspection of the glass items’ surfaces. The relation between the glass technology applied and the glass susceptibility to crizzling are discussed, with reference to the crystal glass technology used in the central Europe. Special emphasis is made on the As and Ca contents as well as on the significance of the As/Ca ratio. Crizzling is a phenomenon described by numerous authors and has been known under this name since the 17th century at least, when Christopher Merret gave the first known description. In the literature, a phase called ‘incipient crizzling’ is sometimes also mentioned.(1) The crizzling is often considered as one of the characteristic symptoms of so called ‘glass disease’ or ‘sick glass’, beside that of the ‘weeping’, which is another well known symptom. That phenomenon has been thoroughly described at the turn of the 19th and 20th centuries. It was just at that time when the first attempts to preserve such glass items were made.(2, 3) Coincidental with the works of Professor J. A. Hedvall in the 1940s and 1950s, a stronger interest was raised in the phenomenon as well as in glass preservation methods.(4–9) The apogee of these surveys was in the 1970s,(1, 10–15) and afterwards the number of publications dedicated to this issue decreased significantly. In 1989 a monograph on glass preservation was published, as an attempt to sum up the entire knowledge on the issue.(16) Since the early 1990s, the interest in sick glass – and in crizzled glass in particular – has been increasing again.(17–26) Symptoms and processes which are characteristic for glass corrosion are mentioned also in relation to the mosaic tesserae, glazes and enamels.(27–29) The number of special conferences which were organised in recent years is confirmation of the increased interest in the problem and in the methods of counteraction among researchers, conservators and museum curators.(30–2) 1
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Knowledge of the phenomenon is crucial for the preservation of the glass heritage. That is why new examination methods are being developed all the time, including methods using sensor glasses for that purpose.(11,15,18,33–38) Attention has also been paid to possible biodegradation processes with regard to unstable glasses(39) as well as to the danger of heating such glass.(40) All these efforts allow for a better understanding of the mechanisms ruling that phenomenon and its origins. However, no antidote has been found so far. Hundreds if not thousands of antique items undergo a continuous and irretrievable decomposition. A number of methods for glass preservation are recommended sometimes in contradiction to one another. Let us mention just one example: a recommendation to use a solution of ethyl alcohol for cleaning the ‘sick glass’.(8,18,19,36) There are attempts to stabilise the surface of the unstable glass mainly by means of various protective coatings.(41–5) The basic role in the protection of sick glasses is still played by climate conditions, mainly the relative humidity, RH, which those glasses are being kept in. Various RH values are recommended related mainly to the potassium carbonate deliquescence point (examples:
