Durability of the artificial calcium oxalate protective on two Florentine monuments

The use of the artificial calcium oxalate treatment providing a protective patina to marble sculptures and a mural façade has been investigated. The longevity of the protective method is controlled at a distance of 3–4 years from its application on two diversely externally exposed Florentine monuments. Micro samples were analysed by optical microscopy (OM), scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX) and MicroRaman spectroscopy to characterize products of deterioration and the efficacy of the applied treatment.Decay is predominately noted at a superficial level and in all cases the calcium oxalate is still present, thus the protective action of the treatment is confirmed and moreover, a consolidant effect is also considered. Both statues present fractures and cavities filled with calcium oxalate residues and various degradation products such as gypsum, lichens and pollution particles. This study contributes to ascertain that artificial calcium oxalate prevents further decay of carbonate materials in urban polluted environments.