The French historical preservation society “Monuments Historiques” has adopted an innovative system for the protection of artistic glass in cathedrals. This system, conceived and patented by the Labor…
The French historical preservation society “Monuments Historiques” has adopted an innovative system for the protection of artistic glass in cathedrals. This system, conceived and patented by the Laboratoire des Monuments Historiques with the collaboration of Herv Debitus, a glass maker specialised in the restoration of monuments, involves the installation of a protective, thermoformed sheet of glass in front of the piece to be protected. This solution allows for the protection of the glazed work from flying objects such as stones, hail, birds etc. as well as thermal shocks, wind, condensation, sulphur from pollution, acid rain and ultra violet radiation which blackens the glass. It also inhibits the growth of micro-organisms. Compared to protective glass sheets which used to be installed a few centimetres away from the glazed frame, thermoformed glass is esthetically more discrete and doesn“t generate reflections or alter the colours of the glazed work. It involves the use of industrial float glass cut to the same dimensions as the pieces in the glazed frame in large electric furnaces (1.45 meters x 2.65 meters) built by Herv Debitus. This allows the molding of the glazed frame to be protected and the fabrication of the protective glass without any risk to the original glazed frame. The thermoformed glass is later covered in coloured coatings which correspond to the colouring in the glazed frame. In successive passes these coatings are largely removed to obtain an almost transparent tint. They remain visible but do not transmit coloured light inside, preserving the original transparency and visibility of the glazed frame. The panes are leaded to complete the finish of the glazed frame. Laminated glass can also be used where greater security is required (eg. Against break-ins, vandalism). While a simple protection of glass 6mm thick weighs 15 kg/square meter, 8.8mm laminated glass has weights ranging from 15.8 to 20.8 kg/square meter depending on the composition of the glass. The surface treatment of the thermoformed glass eliminates unwanted reflections, leaving it sufficiently smooth to make it less subject to dirt. The installation takes place at a distance of from 2.5 to 7 cm from the glazed frame. It“s necessary to find a mounting system either using the original frames or creating a new system. The original glazing frame and the protecting frame can be reinstalled either as a unit or separately. To guard against condensation, openings are provided at the top and bottom of the frame. This new system has already been installed on the windows of the Cathedrals in Tours, Chartres, Poitiers and Ses. Herv Debitus, currently has plans to make glazing frames according to ancient technique described by Antonio di Pisa in a book written in the 14th century.