The microlimate of the Sistine chapel

In recent years the Sistine Chapel has been subject to new microclimatic conditions due to the massive flow of visitors to the monument. At the beginning of this study, the main new risk factors were: artificial lighting, heating, airborne pollutants and release of heat and moisture by the visitors. Study of the microclimate and deposition processes of the particles suspended in the air has been carried out. Experimental surveys were carried out in order to measure the main environmental parameters, their gradiest and rates and show the seasonal and diurnal dynamics of the microclimate and the factors which may cause dangerous microphysical processes affecting the frescoes, i.e. deposition of pollutants, mechanical stresses, microfractures, condensation and evaporation cycles in the micropores. Maps of observed data are extensively discussed in order to point out the microphysical processes responsible for the deterioration of the monument. The main cause of the perturbations include: the presence of the public, the heating and lighting systems and the cleaning methods. The last part of the paper is devoted to comments and suggestions about what has been made or should be done in order to reduce, as far as possible, the deterioration of the monument. After analysis of the problem, some suggestions were made in order to reduce, as far as possible, changes in the natural microclimate but, at the same time, making the Chapel comfortable for visitors and allowing for the maximum exploitation of the work itself without imposing too many restrictions and without exposing the work to excessive risk or damage. Article published jointly with the Bollettino geofisico, Anno 18, N. 2, 1995.