Non-invasive analysis of soluble salts. Preliminary results on the case study of Casa di Diana Mithreum (Archaeological site of Ostia Antica - Italy)

The knowledge of materials and microenvironment has a fundamental role on the preservation of Cultural Heritage. Thermohygrometric conditions as well as a direct contact with water are surely a cause of direct or indirect, i.e. as carrier of soluble salts, of degradation. A new method for a non-invasive analysis of soluble salts (Japanese paper or cellulose pulp) [1], even if already under study, was applied to a wall of the Casa di Diana Mithreum (Archaeological site of Ostia Antica - Italy) and compared with the method currently in use, invasive and relatively dated (UNI 11087/2003). The proposed method only differs from the above cited UNI in the sampling procedure that, further, is not clearly described there. According to the ruled method, Ionic Chromatography (IC) and conductivity measures were performed on the samples while further pH and redox measures were done together with a characterization of materials (bricks and mortar) by Optical Microscopy in polarized light (MOP) and X-ray diffraction (XRD). Results coming from a microclimatic campaign are object of a paper ready to be submitted for publication while here we present those regarding the soluble salts analysis together with the material characterization; obviously a correlation between all data will be looked for in a next future.