A
Associate Professor
Institute of Conservation
Mikkel Scharff
I am a researcher specializing in the making, the material composition, and the gradual deterioration of painted structures, especially canvas paintings. The aim of the research is to devise appropriate means to document and secure our painted heritage for future generations, preferably by ensuring best possible preventive conditions or if necessary through appropriate treatments.
A project in collaboration with Ny Carlsberg Glyptotek: tiny paint fragments found on Greek sculpture, see page 13-40. What does it tell us about the original appearance of Greek sculpture?
Please read an example of research from the Institute of Conservation. We study crack behaviour in old oil paint.
Cracks and multispectral images
A painting, today belonging to "Akademiraadet," was painted by art student Albert Küchler as part of a competition at the Royal Danish Academy of Fine Arts, School of Paintings, in 1825. We have been studying the material composition and the painting technique, as well as the gradual deterioration within the entire structure of the more than 200 year old canvas painting. The structure is composed of a canvas suspended over a wooden stretcher (frame), covered possibly with a coat of gelatine, followed by a coat of a whitish layer (ground layer), and paint layers made a mixture of pigments and drying oil. Using various photographic techniques (multispectral imaging) and X-radiography it has been possible to reveal details of the original pencil drawing, that the artist used to compose the motif before adding the paint layers, and the crack pattern in the painting structure.
The photograph to the left show the painting by Kuchler. The photograph in the centre depicts to the left side a detail (Tobiah and his mother) of the surface of the painting, while the right side of the photograph is made with reflected infrared radiation (IRR) to depict a mixture of the artist's pencil design and the crack pattern, that gradually has appeared in the paint layers. The picture on the right shows the entire face of "Tobiah" only using reflected infrared radiation - by utilizing that technique we could differentiate between cracks that penetrate the entire ground and paint structure, and document micro-cracks that are only present in the border area between the canvas surface and the bottom part of the ground layer.
Recent research has revealed that the crack patterns can be caused by different mechanisms. They can appear a result of the drying of the paint layers, or they can appear due to dimensional changes in the supporting canvas structure, or they can be the result of internal or external physical forces affecting the ground and paint layers.
Results of multispectral imaging can be combined with the results of physical measurements of the mechanical behaviour of the painting structure or paint replicas. Such combined results can be used to make computerized models to predict the long-term behaviour of paintings.
Such combined knowledge makes it possible to better understand deterioration mechanisms and thus being able to better advise preventive means for long time safeguarding paintings.
