Non-destructive Diagnostics of Architectonic Elements in San Giuseppe Calasanzio’s Church in Cagliari: a Test-case for Micro-geophysical Methods within the Framework of Holistic/integrated Protocols for Artefact Knowledge

Historical built heritage is a primary target of low-invasive diagnostics: in fact, it is often characterized by the simultaneous presence of high-value delicate elements and various levels of decay. Here we present the preliminary results of a recent application of micro-geophysical (both by contact and remote sensing) techniques to typical architectural targets such as paint surfaces and stone walls. First, a multispectral survey test has been carried on looking at sample areas of a paint vault with low-cost tools to recognize possible painting layering and pigments gathering. The second target was a vertical profile of a stone pillar, studied by means of very high-resolution and miniaturized geophysical techniques, such as monostatic and bistatic high-frequency georadar (GPR) prospecting and electrical resistivity tomography (ERT, surface and cross-wall configurations). Cross-wall acquisitions (ERT and GPR) were carried out to validate the potential of simpler acquisitions performed from only one side of the investigated wall. This was done in order to check the applicability of the overall procedure to even higher value and sensitive surfaces of historical architectural assets. By means of these micro-geophysical methods we were able to recognize possible discontinuities due to masonry layout and changes in physical properties probably due to moisture presence inside the stonework.