A non-invasive stratigraphic study by reflection FT-IR spectroscopy and UV-induced fluorescence technique: The case of historical violins

n the Cultural Heritage field, stratigraphic analysis is commonly carried out by applying microscopic and micro- analytical techniques to cross-sections of micro-samples taken from artwork. This methodology provides the most comprehensive information on the object's physical structure, but necessarily implies the loss of precious or unique fragments. For this reason, sampling is rarely feasible on musical instruments having such a historical and commercial value as Stradivari or Guarneri violins. Having been played over the centuries, these master- pieces have undergone different kinds of degradation and wear, and subsequent invasive restorations. Varnish layers have therefore been thinned or even removed from the surface and other materials could have been added overlaying the original ones, with consequent variations in coating thickness and composition over time. In the present work, a novel non-destructive and non-invasive methodology combined UV-Induced Fluorescence (UVIFL) photography and reflection FT-IR spectroscopy to investigate how and to what extent varnish thick- nesses vary on the surface of historical violins as well as to reconstruct the stratigraphic layer order and chemical composition. Firstly, UV-induced variations and IR diagnostic bands were identified on numerous model samples reproducing musical instrument stratigraphy. Then the methodology was applied to the study of several Stradi- vari and Guarneri violins and its limitations and strengths were showed in three representative case studies.