Nanotechnology materials to the rescue of stone monuments
Posted: February 19, 2008 Nanotechnology materials to the rescue of stone monuments ( Nanowerk Spotlight ) The list of great monuments and frescoes destroyed or seriously damaged by negligence or criminal action is dramatically increasing, and the biggest culprit is air pollution. Pollutants such as sulfur dioxide and nitrogen oxides are the most serious causes of degradation in carbonate stone, which in the form of marble, limestone and similar materials comprises some of the most important monuments and artifacts in the world. The main damage to monuments is that the stonework becomes sulphated through the transformation of calcium carbonate to calcium sulphate owing to the presence of sulphur dioxide. Two forms of deterioration then take place: the constitution of a black film in areas sheltered from the rain, and elsewhere the crumbling of the interior of the stone. For instance, UNESCO estimates that the surface eaten away annually in a cultural heritage site such as Venice
