Glass underpainting – damage and preventive conservation

Objects with glass underpainting are unique items of folk artistic production, numerously represented in museum collections. In the Czech lands, they started emerging in the 16th century as decorations of monasteries with biblical themes, such as saints with attributes and biblical scenes. From the second third of the 18th century, these motifs became popular as models for folk production. With time, the subjects depicted included portraits and reproductions of outstanding paintings. Underpainting on glass is formed by a coloured layer applied to sheet glass, most often with oil paints, less frequently with water-soluble egg temperas. Glass-painting was not fired, it is a cold painting technique. The technological procedure of underpainting is a reverse procedure of the usual painting on canvas.
In the Historical Museum of the National Museum, glass underpainting items are included in the historical and ethnographical sub-collections. Many of them shows fatal damage which cannot be eliminated despite the current care of restorers. It is the consequence of a number of factors, from unsuitable storage to inexpert handling of these delicate objects. Some of them suffer from the absence of a frame or an underlay. These “bare” glass underpainting items are extremely sensitive especially to the ambient conditions, water condensation and biological attacks. Particularly unsuitable climatic parameters and conditions of the storage environment affect the coloured layer, the glass on which it is applied and the wooden frame which is a part of the underpainting. Regarding the complexity of the issues related to glass underpainting, these objects stand away from the main scope of restorers. There is no research in the Czech Republic dealing comprehensively with the issues of damage and subsequent restoration. This situation is a problem not only for restorers, but also for curators of these objects.
The main objective of this project is, therefore, to map the typical damage of glass underpainting objects and to explain its possible causes. The knowledge obtained will be formulated in a well-arranged atlas which should serve for quick orientation in this issue and the identification of the damage by people who care for these objects and must be able to handle them safely. Only then may the storage conditions of these objects be suitably determined and subsequent restoration care be dealt with. Suitable storage of collections in depositories will help prevent further damage. Based upon information obtained, it will be possible to select a suitable procedure for the restoration intervention.

Project name: Glass underpainting – damage and preventive conservation
Duration: 2017–2018
Agency: National Museum
Project type: Internal grant
NM’s investigator: Bc. Pavla Glauningerová

Anticipated results/outputs:
The project results will be published in an expert article in a peer-reviewed journal and in the form of two papers at conferences. The main output of the project will be the elaboration of an atlas of the damage caused to underpainting on glass which will form an attachment to the planned methodology “Caring for underpainting on glass in museum collections”. The elaboration of this methodology has been a long-term objective of the applied research of the Department of Care of Historical Museum Collections. Besides the results obtained from this project, it will also include a follow-up research testing the currently available restoration capabilities.