Preservation of medieval stained glass with regard to special material and environmental factors

The stained glass panes in the High Chancel of the Erfurt Cathedral are among the most valuable of their kind in Germany. Yet these panes, which were manufactured in the Middle Ages, were threatened by adverse environmental effects. A mineralized film had formed on the outside of the windows which significantly reduced their translucency, legibility and brilliance of colour. In some cases, the depictions on the windows were barely recognizable.

The KUR project was faced with a new challenge when conservation work began on the first windows on the north side; the conservators discovered that work had been carried out on the inside of the panes between 1909 and 1911 which would affect further conservation work. In preliminary scientific tests, the panes were analyzed to assess the extent of damage and help determine the optimal method of conserving them. Furthermore, the tests shed light on environmental effects and previous conservation measures which were believed to be causes of damage to stained glass of this kind elsewhere. An innovative 3D monitoring system was introduced to monitor weather corrosion in the future. Experts received valuable information for preserving other stained glass treasures.

Project administrator:
Erfurt Cathedral, St. Marien – cathedral chapter

Cooperative partners:
Federal Institute for Materials Research and Testing, Berlin
Otto-Friedrich-Universität Bamberg