Glass cathedral

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. 

Clusters of metal atoms can form colloidal suspensions. Colloidal clusters of copper, silver, and gold in glass are responsible for some of the vivid colors of stained glass in medieval cathedrals. Even aqueous suspensions of metal clusters are known (Fig. 8.45). 

Figure 5.11 Plot of 87Sr/86Sr vs eNd for some examples of English Medieval cathedral window glass. (Wilson, Pollard and Evans unpublished data key in Table 5.4)...

Figure 1. Stained glass from Chartres Cathedral (in the Museum of Art, Princeton University). The top left quarter is from a thirteenth-century window depicting the martyrdom of St. George.

Frankl, P., The Chronology of the Stained Glass in Chartres Cathedral, ... 

Stohlman, W. F., A Stained Glass Window from Chartres Cathedral, Bull. 

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 1. Six intact glass quarries, from Elgin Cathedral, and eight variously colored glass fragments from Elgin Cathedral (EC), Holyrood Abbey (HA), St, Andrews Cathedral (StAC),and Melrose Abbey (MA).

Figure 4. Correlation between the potash and magnesia level (as weight percentage) in plant ash and glass from Elgin Cathedral ( ), Holy rood Abbey (a), St Andrews Cathedral ( ), and Melrose Abbey (m).

It was once considered that direct evidence of the long-term flow of a glass was provided by the variation in thickness of the glass found in ancient cathedral windows. However, modem studies of this hypothesis have instead found that the thickness variations are most likely the result of manufacturing processes for the panes combined with the craftsman s propensity for placing the thicker edge of the pane down. For more details, see R. C. Plumb, Antique windowpanes and the flow of supercooled liquids, J. Chem. Educ., 66, 994-996 (1989). See also problem 7, this chapter. 

Open-ended) If the ancient craftsmen had used polycarbonate in cathedral windows instead of glass, calculate the expected thickness variation after 1500 years in a pane 25 cm high that was initially uniform. Assume that the pane is rectangular and is not constrained by its frame except vertically at the bottom edge to keep the pane from falling. See Chapter 2 for hints on converting E t) to D(t). Carefully list all assumptions and approximations as part of your answer. 

Figure 1 A stained glass window from Cologne Cathedral, 16th century (Picture provided by Dombauhuette Koeln, Germany.)...

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