Lost works of art uncovered with terahertz scanners

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Scientists from Fraunhofer Institute for Material and Beam Technology (IWS) in Dresden, Germany have demonstrated how terahertz scanners can be used in art restoration. A project, sponsored by IWS, the Academy of Fine Arts Dresden, the Research Institute for Monument Conservation and Archeometry, and the Technical University Dresden, used the scanners to gain important information about the layered structure of a wall painting by Gerhard Richter in the Dresden Hygiene Museum.

The picture, which was painted shortly before the artist left the German Democratic Republic, was believed lost, as in the 1960s it was painted over. The scanner provides concrete data on the structure of the individual paint layers or of potential hollow areas in the wall. In this way the device indicated in the Hygiene Museum that in one area the plaster on the wall had evidently been repaired, a valuable clue for the restorer.

Michael Panzner of Fraunhofer IWS developed the terahertz detector, which uses short electromagnetic pulses that penetrate the various materials almost without attenuation. Materials will display characteristic absorption lines, which can be used to identify them.

A further application for the scanner is detecting organic biocides, which, in the 1970s, antique textiles or wood sculptures were sprayed with to keep them from being destroyed. Now, many museums cannot exhibit these works of art in public, because these agents pose a health hazard.

Fraunhofer IWS, together with further partners, now wants to set up a project to examine the possibilities and limits of the terahertz technology for detecting organic biocides. ‘In contrast to the current x-ray fluorescence analysis which works on an element-selective basis, terahertz scanners recognise substances on the basis of the molecular bonding structure. Organic biocides, in particular, could be differentiated in such a manner,’ explained Panzner.

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