Characterization of patinas from the main façade of Palacio del Infantado (Guadalajara, Spain)

Abstract

Patinas have been deeply studied during the last years. However, every new case has its own importance as it happens with the study of mortars or other building materials. In this case the scarce remains of the orange patina that covered some parts of the main façade of the “Palacio del Infantado” (Guadalajara, Spain) -figure 1- have been studied. The main aim, apart from knowing the characteristics of the patina, was to determine whether it would be necessary to preserve it in further interventions. For this purpose fragments – scales- smaller than 1 cm2 were sampled. Color properties were determined by means of an spectrophotometer; and patina samples were characterized by different microscopy techniques such as Optical Microscopy (OM), Fluorescence Microscopy (FM) and Scanning Electron Microscopy with coupled Energy Dispersive X-Ray Spectroscope (SEM-EDS). Thank to these techniques up to three layers have been distinguished in the patina. Besides, the mineralogical analysis revealed that the main composition of the studied patinas was calcium oxalate (whewellite) hydroxyapatite, calcite and gypsum. These results together with other obtained in the study point out that these patinas are similar to those described in the literature as calcium oxalate and calcium oxalate patinas. As a consequence this patina should be preserved in future interventions since it is recommended in several international charts.