Laser-clean windows
Researchers have established that lasers are useful tools for the conservation and restoration of stained glass windows, provided a thorough determination of suitable irradiation conditions for each one is made beforehand. Specific laser settings may be needed for the different forms of damage caused by sunlight, water, wind, dirt, temperature changes and air pollution. The work was done as part of the 'Laser technologies in the analysis, conservation and restoration of historic stained glass windows' (LASERGLASS) project. This required a complex study on the interaction between corroded glass and lasers, by varying parameters such as wavelength and frequencies. The aim was, as one would expect, to find the best cleaning method without causing damage to priceless examples of European cultural heritage.The researchers studied historic stained glass windows of varying ages from different locations in Poland to see if laser cleaning would be effective. The work carried out on model samples and on the windows themselves demonstrated that irradiation with one pulse from a Nd:YAG laser could successfully remove contamination and corrosion layers. One Polish church had glass covered in thick layers of corrosion products; a second window panel from elsewhere in the country had a corrosion crust, as well as dirt and polymer layers; the third glass, which was a colourless section of a larger window, carried a superficial layer of dark dirt. Nevertheless, the Nd:YAG laser worked on them all.Post-irradiation a variety of sophisticated laboratory tools were used to analyse the results. LASERGLASS found that careful assessment in advance of the irradiation conditions for each individual case and online control of the irradiation process were the keys to success.Stained glass is an often-irreplaceable part of European heritage, and these research results form a valuable contribution to its conservation. Museums, craftspersons and those responsible for maintaining church buildings could all benefit from this work, while the general public will be able to enjoy the full play of light through the newly cleaned windows.
