A multi-analytical non-invasive approach to violin materials: The case of Antonio Stradivari “Hellier” (1679)

The study and characterization of the materials of historic musical instruments, especially violins, represent an important aim for scientists and conservators. In particular, the varnishes have been often investigated, even to correlate their chemical characteristics with the sound produced by instruments. However, in the last years, the attention has moved to the study of those materials (inlays, pigments, binders, fillers, glues) used by important ancient violin makers, as Antonio Stradivari, to decorate the musical instruments in order to confer a higher aesthetic value. Because of the importance of the ancient violins, the analytical investigations have to be performed more and more with non-invasive methodologies, and this could be a strong shortcoming for the complexity of the materials to study. Therefore, the scientific research has improving new methodological approaches that could provide several results without touching the violins. The “Hellier” violin (1679), actually held in Museo del Violino of Cremona (Italy), is one of the most important violin made by Antonio Stradivari and represents a perfect example for the study of both varnishes and decorations. This contribution focuses on the materials' characterization through different totally non-invasive diagnostic techniques: UV-induced visible fluorescence imaging, optical microscopy, reflection FTIR spectroscopy, and XRF spectroscopy. In particular, reflection infrared spectroscopy has been applied for the characterization of several organic substances historically used to make the musical instruments, with the aim of achieving a correct interpretation of the violin varnish spectra. The varnishes, the black strips of the purflings, the black fillers, and the white decorations of the inlays were investigated. The preliminary results suggest the presence of (i) supposed resinous drying oil varnish, (ii) metal-based ink used to dye the black filler of the inlays and the black strips of the purflings, and (iii) bone or ivory as material for the white decorative elements of the inlays.