Non destructive investigation of historical plaster and stonework in San Giovanni dei Napoletani Church in Palermo (Italy): evaluation of the exchange between architecture and environment by thermography and radar survey

Abstract

Historic plasters will be increasingly at risk, due to natural alteration as well as renovation projects when internal and external plaster is refused and refaced. To sensibly conserve as much as possible of the historic substance, the preliminary inquiry is very important to get a profound knowledge of the integrity of materials and their decay, and to decide how to restore them. The application of NDI like infrared thermography (IRT) and radar investigation can be a reasonable support to evaluate the relationship between interior and exterior plaster, the microclimatic exchange in the architecture surfaces and the related alteration of materials. In fact they’re used for the detection of problems with isolation, to detect evaporating humidity flows on the surface of buildings and to locate adherence loss and cavity of plasterlayers. Thermography and radar survey had been applied to study the facade of San Giovanni dei Napoletani church in Palermo (Italy) during a collaboration between the Department Denkmalpflege of the Technische Universität Berlin and the L.I.R.B.A. Laboratorio di Indagini e Restauro dei Beni Architettonici of the University of Palermo. The main line for the thermographic measurement was to get a profound knowledge about the current status and damage of the plaster and stonework; in addition the radar investigation was of interest to underline the achieved results. It was possible to locate various damage like adherence loss and cavity between the layers of the plaster and humidity at the surface, which was not visible. Another important focus of the contribution was to study the influence of different climatic conditions at different times of day during thermographic measurements. The three studies which were carried out from September to November 2007 generated an interesting variety of results.