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<p class="Abstract">This paper presents a long-term in-situ campaign to monitor contemporary bronze statuary exposed outdoors. The case study relates to the characterisation of three sculptures belonging to the Gori Art Collection, located in the Fattoria di Celle: ‘Cavaliere’ and ‘Miracolo – Composizione’ by Marino Marini and ‘Due forme o due ombre n°2’ by Luciano Minguzzi. The overall conservation state of the sculptures was investigated by means of a multi-analytical and non-invasive approach, involving different techniques. Three-dimensional photogrammetry was performed to fully document the artworks. The chemical and microstructural features of the corrosion patinas were then characterised through X-ray fluorescence and Raman spectroscopy. In addition, the stability and the protective effectiveness of the corrosion products were assessed by electrochemical impedance spectroscopy. Thanks to the combined use of these specific techniques, the information extracted through the different analyses could be correlated with each other and with the exposure conditions. The different corrosion products were identified as being primarily copper sulphates and phosphates, and they were correlated with the different microclimate conditions related to their location on the statues. The information gathered from the presented multi-analytical approach represents the fundamental knowledge required to develop a tailored conservation project to assure the long-lasting preservation of these artworks.</p>

A series of clinopyroxenes along the CaMgSi2O6–CaCoSi2O6 join was synthesized by quenching from melts at 1500°C and subsequent annealing at 1250°C (at 0.0001 GPa). This protocol proved to be the most effective to obtain homogenous, impurity-free and stoichiometric pyroxenes. Electron microprobe analyses in energy dispersive mode were conducted and single-crystal X-ray diffraction data were collected on Ca (CoxMg1-x)Si2O6 pyroxenes with x = 0.2, 0.4, 0.5, 0.6. Effects of cation substitution at the M1 site are described. The experimental findings of this study allow us to extend the comparative analysis of the structural features of pyroxenes with divalent cations at the M1 and M2 sites.

The Raman spectra of the end member pyroxenes CaZnSi 2 O 6 and Zn 2 Si 2 O 6 are calculated by quantum mechanical modeling and compared with the experimental ones measured in synthetic (Ca x Zn 1−x )ZnSi 2 O 6 pyroxenes with x = 0, 0.2, 0.3, 0.5, 0.7, 1. The calculated spectra correctly predict the intensity and peak positions of the spectra recorded on the end members. The model provides also useful hints for the mode assignment at the intermediate compositions. The experimental peak positions are compared in (Ca x M 2+ 1−x )M 2+ Si 2 O 6 pyroxenes, with M 2+ = Mg, Co, Zn, Fe 2+ . These pyroxenes share a common charge and different mass and ionic radius; the relative contributions of the mass and ionic radius in the experimental spectrum are discussed in four of the most intense peaks. We found that the positions of the strongest peaks are related to the average bond distances of the polyhedra which most affect a given mode. Ca-Zn pyroxenes provide an exception, whereas the CaZnSi 2 O 6 end member fits quite well in the bond-distance/peak positions relations found in other pyroxenes, and the same does not occur as Zn exchanges for Ca. Peak broadening occurs in Zn pyroxenes in intermediate compositions; it is related to the presence of polyhedral local configurations around Zn and Ca atoms in the M2 polyhedron. The broadening is higher in the ~ 1010 cm −1 peak (ν 19 ), which, among the strongest peaks, shows the highest difference in the Raman wavenumber between end members. The different behaviours of Zn pyroxenes with respect to Mg, Co, and Fe 2+ ones are likely related to the partially covalent bonding in the M2 cavity shown by Zn pyroxenes.

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