ARTICLE ARTICLE VOL. 33 NO. 2 (2021) Surfing through the coating system of historic bowed instruments: a spectroscopic perspective Giacomo Fiocco, a,b Claudia Invernizzi, a,c Tommaso Rovetta, a Michela Albano, a,d Marco Malagodi, a,e Patrizia Davit b and Monica Gulmini b a Laboratorio Arvedi di Diagnostica Non Invasiva, CISRiC, Università degli Studi di Pavia, Via Bell’Aspa 3, 26100 Cremona, Italy b Dipartimento di Chimica, Università di Torino, Via Pietro Giuria 7, 10125, Torino, Italy c Dipartimento di Scienze Matematiche, Fisiche e Informatiche, Università degli Studi di Parma, Parco Area delle Scienze, 7/A, 43124 Parma, Italy d Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy e Dipartimento di Musicologia e Beni Culturali, Università degli Studi di Pavia, Corso Garibaldi 178, 26100 Cremona, Italy DOI: 10.1255/sew.2021.a8 © 2021 The Authors Published under a Creative Commons BY-NC-ND licence Which materials did the great Cremonese violin makers use to coat their violins? Is it possible to determine the secret reci- pes jealously guarded by the luthiers in their workshops? Although almost three centuries have passed since his death, the myth of Antonio Stradivari still represents the epitome of violin making. Indeed, every violin maker has the ambition, more or less declared openly, to build instruments similar to those produced in the Cremonese work- shops in the 17 th and 18 th centuries. Stradivari lived for 93 years and after his death Cremonese violin making progres- sively decreased in quality and quan- tity. This decline has inevitably led to the loss of traditions and knowledge, creat- ing a deep gap between historical and contemporary lutherie. Since the second half of the 20 th century, however, luthiers who aspired to be scientists and scien- tists with a passion for musical instru- ments proposed more or less convincing hypotheses concerning the materials used by the great masters. 1 Only in the last few decades has scientists’ inter- est in musical instruments grown, and the increasing historic (and economic) importance of ancient violins has fuelled the scientific debate on how to approach the investigation. Technical peculiarities of these artworks have been studied, 2,3 with the main focus on the nature of the fine Cremonese varnish and of the other materials involved in the overall finishing treatment. 4 It is known that multiple varnish layers were applied to the wood, which had been pre-treated with a sealer to prevent varnish penetration. In addition, μm-sized inorganic particles are some- times dispersed in the coating system. The most common materials involved in the finishing processes were sicca- tive oils, natural resins, casein or animal glues, inorganic fillers, organic and inor- ganic colourants. 5 Furthermore, other substances such as benzoin or shellac resin were commonly used on ancient violins—and still are in contemporary ones—as surface polishes for conserva- tion, restoration and maintenance. 6 Despite some similarities with other painting techniques, the finishing of wooden, bowed string instruments has peculiar purposes and characteristics. In particular, the varnish must not only be a protective layer, but it should be coloured, transparent and glossy, in order to enhance the wood features. A number of colourants (pigments, lakes or dyes), normally spread at very low concentra- tion, or specific pre-treatments can be employed to obtain the typical shades of the varnish. Spectroscopies based on infrared radi- ation and X-rays are perfect candidates for the study of these materials as they enable the identification of both organic and inorganic chemical species. Fourier transform infrared (FT-IR) spectroscopy specifically identifies the functional groups mainly related to the organic materials and to some inor- ganic components (e.g. carbonates, silicates, sulphates) of the layers. As for bowed string musical instruments, where sampling is often impossible, the use of portable non-invasive reflection SPECTROSCOPYEUROPE 19 www.spectroscopyeurope.com