A MULTIDISCIPLINARY APPROACH FOR THE CONSERVATION OF A BUILDING OF THE SEVENTEENTH CENTURY

A long-term multidisciplinary conservation study is actually in progress inside the Villa della Regina, a prestigious Savoy residence built in the seventeenth century and recently restored. The walls of some rooms of the Villa are decorated with precious tin-mercury mirrors, that are baked with a reflective coating constituted of a tin-mercury compound surrounded by liquid mercury. The reflective layer is very soft, thus any restoration is difficult to be performed and can lead to a complete destruction of the artifact. Amalgam corrosion is a very slow process and, although there is no way to prevent the oxidation of the reflective layer, the conservation state of the artifacts may be improved by keeping them in a controlled environment. For this reason, a monitoring system has been designed and installed that is based on a wireless network of extremely compact sensors, for temperature and relative humidity measurements. The sensors have been specifically designed to satisfy the requirements for use in cultural heritage field and the system allows one to automatically collect the data that can be analyzed with the final aim to establish a correlation between the environmental conditions and the conservation state of the artifacts. A restoration has been carried out by producing in situ an amalgam inlay on the corroded area to slow down the release of liquid mercury in order to avoid also possible unsafe conditions for staff and visitors. In addition, a sensor has been developed which is based on a prototypical plastic optical fiber for the detection of low concentration Hg vapors to ensure the safe conditions in the Villa rooms. The sensor is being tested in laboratory.