It is primarily glass from the 19th Century, particularly amber-colored glass, which is often affected by the damage phenomenon of micro-fissuring or crizzling, also called »craquelé«. This process destabilizes the glass and affects its light reflection. The cooperating partners Metropolitan Chapter of Cologne Cathedral and the Fraunhofer Institute for Silicate Research (ISC), Würzburg, investigated character, causes and process of the still unexplored damage pattern »craquelé«. Innovative methods and materials for consolidation and restoration of micro-fissured glass were tested on both, model glasses and originals. The investigations showed that »craquelé« involves a system of tiny fissures of only a few micrometers width that can be filled by corrosion products. Additionally, the existence of »gel layer canals« was proved, that is, offshoots or runners from the gel layer in the underlying core glass. For the consolidation of the micro-fissured glass, the use of a hydroactive gel developed by Fraunhofer ISC, and the lodgment of fiberglass fabrics and nonwovens were tested. The fiberglass fabric solution was implemented for the »craquelé«-damaged portions of the »Jesus Sirach window« in Cologne Cathedral.

Project implementation:

Metropolitankapitel der Hohen Domkirche Köln
Dombauverwaltung
(Glasrestaurierungswerkstatt)
Roncalliplatz 2
50667 Köln
ulrike.brinkmann@dombau-koeln.de
www.dombau-koeln.de

Cooperation partner:
Fraunhofer-Institut für Silicatforschung Würzburg, Bayern
www.isc.fraunhofer.de
 

AZ 24583