Production techniques in modern sacred art: a study of mural paintings through physical chemical characterization and statistical analysis

The main objective of this study is to allow a thorough knowledge of the materials and the production techniques in modern mural paintings, focusing on sacred art created in Veneto parish churches by local artists and still little known. This research, in fact, aims also to the valorisation of local cultural heritage which has been often labelled as “work of art by a minor artist” and condemned to oblivion. Five murals by different painters (L. Pavan, G. M. Lepscky and B. Rossato), dating from 1893 to 1969, have been investigated by the joint use of several analytical methods, such as Optical Microscopy, Scanning Electron Microscopy with electron microprobe (SEM/EDS), X-Rays Fluorescence Spectrophotometry, Fourier-Transform Infra-Red Spectrophotometry (FT-IR), Termogravimetry (TG), Differential Scanning Calorimetry (DSC) and Gas Chromatography–Mass Spectrometry (GC-MS). Although having been produced quite recently, these paintings are subjected to degradation processes and restoration treatments are in most cases needed. The analytical results show a great variety in the use of traditional and new materials: the choice of plasters, pigments and binding media reflects the transition between traditional and modern and contemporary art. Even though these murals have been always considered frescoes, the analysis by GC-MS after hydrolysis and derivatisation steps highlight the use of organic binders, in particular egg, oil and mixed tempera. The data have been treated by different multivariate chemometric techniques, such as cluster analysis, principal component analysis (PCA), in order to classify the binders on the basis of the organic material used.