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Corrosion, soot, bacteria and fungus all cause damage to the valuable stained-glass windows found in old churches. Special care must be taken when cleaning them. A laser tool should in the future allow surface deposits to be removed gently, layer by layer.
At Christmas many people make their way to church, and have a chance to admire the beautiful stained-glass windows that decorate many an ecclesiastical building. For over a thousand years, church masons have commissioned artists to produce stained-glass windows to embellish their edifices. But corrosion, soot, dust, bacteria and fungus have dimmed the brilliance of these historical masterpieces. If not restored, they will be lost for ever to future generations. In cooperation with scientists from the Laser Centre at the University (FH) Muenster and sthe Material Science Department of the University of Erlangen, researchers at the Bronnbach Branch Laboratory of the Fraunhofer Institute for Silicate Research ISC are working on ways of using excimer lasers to remove particularly hard and well adhering deposits without damaging the underlying surface. The project was funded by the Deutsche Bundesstiftung Umwelt, Osnabrueck.
The majority of deposits on stained-glass windows can be removed by specialists working with extreme care, using fine brushes, scalpels and solvents. But the removal of more hard and well adhering deposits, such as chemical incrustations caused by corrosion or added layers of synthetic varnish, has always been a problem. Even these deposits can be removed using the techniques developed at the ISC. "We can use the laser to remove deposits from stained glass with a high degree of accuracy. This is particularly important, because the upper surface of the glass builds a gel layer that protects the stained glass from deeper damage. This gel layer must not be damaged", describes Peter Mottner. To clean the works of art, the researchers use a conventional excimer laser, of the type normally employed in the manufacture of electronic circuits. It has been modified by the laser specialists at the FH Muenster, so that it is more adaptable and can be applied to more precisely defined areas of a surface. The researchers have carried out numerous experiments, varying the energy fluence, repetition and pulse nimber of the laser, to analyze the parameters that are needed to remove specific types of deposit from specific types of glass. "In the beginning, we used representative samples of glass; now that we have established that the method is well suited for the removal of corrosion deposits, fungal damage and bacteria, we are also starting to work with small samples taken from original material", says Peter Mottner. Cleaning is only the first stage in the restoration of stained glass. To ensure that visitors to churches can continue to enjoy the spectacle of fine stained-glass windows a century from now, professional restorers spend up to one year working on a single window.
For further information:
Phone: +49 9 31/41 00-7 11
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Phone: +49 9 31/41 00-1 06
Fax: +49 9 31/41 00-3 99
© Glasmalerei Peters, Paderborn.The appearance of a stained-glass window can be severly impaired by ...
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