Medieval window glass

Pollard, A. M. (1979), X-Rays Fluorescence and Surface Studies of Glass with Application to the Durability of Medieval Window Glass, Ph.D. thesis, Univ. York. 

In an analytical study of the relationship between the chemical composition and corrosion behaviour of Medieval window glass from York Minster (Pollard, 1979), a total of more than 200 samples were analysed, dating mainly from the 12th, 14th and 15th Centuries. A summary of the findings has been... 

Table 5.4 Values of sNd and 87Sr/86Sr for eight samples of Medieval window glass. (Wilson, Pollard and Evans unpublished data.)...

Figure 9.9 REE abundances from archaeological glass, showing the effect of chondrite normalization, (a) shows the raw abundances of the REE measured on a set of English medieval window glasses, with the saw-tooth pattern evident, and little indication of differences between any of the samples (apart from perhaps one which has lower overall REE concentrations), (b) shows the same data normalized to the chondrite data (Table 9.1). The saw-tooth has largely disappeared, and close inspection suggests that two samples have a positive europium anomaly, possibly indicating a different geographical origin.

Table I lists analytical data on specimens of our set of random samples (Figure 10) which were selected to show the range of compositions which can characterize medieval window glass. Because of the marked differences in the concentrations of the constituents shown in this table, it is not likely that medieval glass of unrelated origins would be closely similar in composition.

Vassas, C. D., Chemical, Thermal-Analysis, and Physical Study of Glasses of Medieval Stained-Glass Windows, Int. Congr. Glass, Artistic Hist. Commun., 9th, 1971 (1972) 241-266 (French). 

THE glorious medieval stained-glass windows of European cathedrals have been the subject of several chemical analyses to support conservation projects, to identify workshops and their practices, and to attempt the association of colors with specific metal ions in various oxidation states. However, little information of this sort has been generated from the beautifully decorated, enameled, and gilded copper ecclesiastical objects used in medieval cathedrals that are recognized under the generic name of Limoges enamels. 

Figure 5 Medieval stained glass window from Erfurt (Germany) with a dense crust of weathering products, a cross section, SEMpicture (left) and element mapping (EDX) (right) (Note elements are specified in the picture (Ca, K, S, Si))...

Degradation processes in medieval stained glass windows have been studied using FT-IR spectroscopy and the pigments applied to early specimens have been characterized using the FT-Raman technique. Similar methods have been used to study early enamels and cloisonne specimens. 

The belief that a glass is a supercooled liquid in which atomic motions have slowed to the extent that characteristic relaxation time exceeds the observation period (1000 years for stained medieval windows) is debated and the possibility that glass corresponds to a... 

The decreasing levels of SO2 and increasing frequency of car traffic has resulted in a new multi-pollutant situation in many urban and industrial areas. In order to possibly quantify the corrosion effects caused by this new multi-pollutant situation an extended exposure program was performed that took place between 1997 and 2001 and involved some 30 test sites in 18 countries in Europe and North America [91]. Specimens of carbon steel, zinc, copper, bronze, limestone, paint-coated steel, and glass representative of medieval stained glass windows were exposed for up to four years. At each site, the environmental data measured included climatic parameters (temperature, relative humidity, and sunshine radiation), gaseous pollutants (SO2, NO2, HNO3, and O3), particles (presented as PMio, i.e., concentration of particles with diameter < 10 pm), and precipitation (total amount, conductivity, and concentration of, i.e., H+, S04 , N03, Cl", NH4+). 

The windows in some medieval cathedrals show greater thickness at the bottom than at the top, owing to the slow flow of the glass under the influence of gravity. 

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