Restoration of a sandstone facade: from the project to the monitoring

This work describes the restoration of a facade of an historical building, constructed from typical local sandstone, characterized by different subsequent decay phenomena and subjected in the past to a conservation treatment. The sandstone was characterized, the quarry of provenance was identified, and the causes of the different decay phenomena were investigated. Potential commercial products for the restoration were tested first in the laboratory, then in situ selected products were applied and the effectiveness of treatment was subsequently monitored. Analytical methodologies such as X-ray diffraction (XRD), observation of thin sections under polarized microscope (OM), Fourier transform infrared spectroscopy (FT-IR), micro-Raman spectroscopy, and water absorption tests were employed in the laboratory, while nondestructive tests, performed with portable instrumentation such as colorimeter and sponge contact, were carried out in situ.