Methods of microbiological control of the mural frescoes: the example of the restoration of the Sistina chapel

The microbiological investigation carried out during the restoration of Michelangelo's vault in the Sistine Chapel has the goal of determining microbic species on the frescoes before and after conservation and restoration. The study is important in considering the introduction of techniques of asepsis during the treatment, monitoring the microbiological content of the materials used, and evaluating the suitability of the sampling techniques. The microbiological results from the painted wall before restoration show a habitat of a moderate quantity of microorganisms, mostly originating from the environment. On the other hand, the bacterial (but not fungal) contamination of the vault (mostly through microorganisms from humans) was demonstrated after the restoration activities, which were carried out without particular precautions of asepsis. Following the introduction of asepsis techniques in the restoration activities, the results show less remarkable contamination of the vault. The specimen techniques, using traditional methods, revealed a low quantity of microorganisms, in addition to presenting ethical and practical problems in collecting sufficient quantities of the precious materials. It seems necessary, therefore, to reorient the sampling techniques toward a nondestructive system (plate "rodak contact" method), in order to respect the integrity of the fresco. Discussions are still continuing about the validity and feasibility of the methods used in the collection of microbiological samples.