Spectroscopic characterization of xx century mural paintings of punta begoña’s galleries under conservation works

Abstract

A multi-analytical approach based on the combined use of non-destructive spectroscopic techniques and micro-destructive techniques is presented, not only to characterize the mural paintings of Punta Begoña galleries (Getxo, Biscay, Spain), but also to fill the gaps found in the historical documentation. The galleries were built in 1918 for Horacio Echevarrieta, a spanish republican businessman, and are in the list of protected historical buildings of the Basque Country. The whole building is composed by two galleries and a main hall with francoist iconographies in their walls, which disagree with the owner’s ideology, painted around 1938 after the occupation of the building in the Spanish Civil War. There is a lack of historical information about the original aspect of the mural paintings (1918 decoration) or the nature of the observable paintings (1938 over paintings). Thanks to the analysis carried out by optical microscopy, Raman spectroscopy, X-ray fluorescence (XRF), Fourier Transform Infrared spectroscopy (FTIR), Scanning electron microscopy coupled to electron scattering X-ray spectroscopy (SEM-EDS) and X-ray diffraction analysis (XRD), it was possible to identify under the painted layers a lead white preparation layer. Then, the original mural pigments were identified being of a silicate nature due to the systematic presence of presence of Clinochlore in all the colours. Regarding the over painted panels, their characterization revealed pigments that did not fit with the contemporaneous pigments, common practice in the francoism regime. In addition, carnauba wax could be identified as the binder. Moreover, the main decaying pathways of the materials were pointed out. These results will help to provide a new vision of these mural paintings, and the whole building. However, the most important achievement was the historical contextualisation of the main hall, which could help to change the historical perception of this heritage, putting the analytical chemistry at the service of history.