Reflectance Spectroscopy as a Non-invasive Technique for Preliminary Characterization of Soluble Salts on Historical Masonries

The presence of soluble salts due to rising damp triggers significant damage to brick masonries, and their distribution needs to be effectively assessed before targeting maintenance intervention. For this purpose, a novel non-invasive approach based on reflectance spectroscopy analysis has been proposed for the preliminary characterisation of soluble salts on masonry surfaces by using a portable spectroradiometer, working in the visible-short wave infrared (Vis-SWIR, 350 ÷ 2500 nm) spectral range. The setup of the technique included the analysis of powdery samples: pure salts, salts mixtures, salts blended with brick powder. Then on field application on a Venetian palace, subjected to rising damp of salty water, was carried out. The results highlight the feasibility of the methodology both in the laboratory and in situ: thanks to instrument portability, low cost, and an adequate possibility to detect salts this technique helps in the planning of the preservation project.