Non-invasive mobile technology to study the stratigraphy of ancient Cremonese violins: OCT, NMR-MOUSE, XRF and reflection FT-IR spectroscopy

It is generally believed that the modern violin has emerged in Italy in the first half of the 16th century. The scientific study of its complex stratigraphy began approximately in the 1980's with invasive standard methods. Only since the last decade or so, the focus of diagnostic investigations has been increasingly shifted towards the use of non-invasive approaches in order to preserve the value and the integrity of these masterpieces. In this work, precious historical Cremonese violins made during the Italian Baroque period by the great master luthiers of the Amati, Stradivari and Guarneri families were non-invasively analysed for the first time by combining Optical Coherence Tomography (OCT), reflection FT-IR spectroscopy, X-Ray Fluorescence (XRF) and Nuclear Magnetic Resonance (NMR-MOUSE). Portable instrumentation allowed non-invasive on-site analyses of the violins preserved at the Museo del Violino in Cremona. The aim of this wide multi-technique campaign, carried out within the MOLAB Transnational Access - EU H2020 Project IPERION CH, was the characterization of the stratigraphy from the innermost wood treatments to the outermost varnish layers. OCT provided information about thickness and number of layers, as well as detecting dispersed particles; FT-IR spectroscopy identified the molecular composition of the layered materials; XRF brought elemental information about finishing coats (i.e. pigments and fillers) and pre-treatment procedures; and the NMR-MOUSE investigated the wood density and elasticity, revealing wood treatments at the inner and outer surfaces of the plates. The collected results allowed one to gain deeper insight into the ancient processes adopted in the Cremonese violin making workshops during the considered period and subsequent restoration efforts.