Monitoring of protective products on Peperino stone using portable devices

The aim of the research presented in this paper is to monitor the stability of three protective products applied on samples of Peperino stone, a volcanic tuff widely used for the historic buildings and architectural elements in Viterbo (Italy), using portable devices. More in detail, two different monitoring techniques were applied: VIS-NIR point spectroscopy (400-1000 nm), and colorimetry. In order to characterize the compositional variability and homogeneity of the samples, X-ray micro- fluorescence (micro-XRF) was preliminary used. Data were acquired before and after the application of the different products in order to monitor and detect the efficiency of the considered low-impact products. Peperino samples were also aged in a Solar Box chamber for 1000 h to simulate a solar irradiation and measurements were repeated at the end of the ageing period to evaluate the stability of the protective products.