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A 3D trip into the violin varnish - Physicists and chemists ally to bring back the forgotten secrets of ancient violin-makers

Ancient Masters of Italian violin-making workshops developed peak quality techniques, still testified by the tonal excellence and amazing appearance of their instruments. Few records give scarce information about the original recipes for finishing the instruments, as technical secrets were orally passed to apprentices. Scientific investigations represent nowadays powerful tools to rediscover the lost recipes, and scientists have invested effort in setting up new analytical schemes and innovative techniques for probing the instruments in order to properly identify materials used for their finishing.
In a new study published in EPJ Plus, Giacomo Fiocco affiliated with both Pavia and Torino Universities, in Italy, and colleagues have developed a non-invasive approach to catch a 3D insight into the main morphological features of the overlapping finishing layers, linking the morphological images with the chemical nature of coating system. 
This newly developed method could help scientists to rediscover the procedures and materials employed, in order to reproduce the multi-layered coating systems of the ancient Masters and to properly preserve their masterpieces. To smooth and seal the wood, violin makers typically used multiple applications of ground minerals, such as calcium sulphates, calcium carbonates and silicates, dispersed in a protein-based binder, such as casein or animal glues, to fill up the wood pores before applying several layers of varnish, made up of natural resins dissolved in alcohol, volatile oils (fig. 1).
In this study, the authors relied on phase-contrast Synchrotron Radiation micro-Computed Tomography (SR-micro-CT), used for the first time for this specific purpose. The approach involves X-rays produced at the SYRMEP beamline of Elettra, originally designed for the medical field. 
 

Figure 1.  3D reconstructions of sample models with different inorganic particles embedded in the ground coat below the varnish layer (left to right: chalk, kaolin, gypsum).

The authors use the X-rays of the SYRMEP beamline to scan two sets of mock-ups mimicking the finishing layers of historical instruments, in order to optimise the instrumental settings, boost the spatial resolution and define reconstruction parameters. They then consider a large fragment removed from a damaged cello by 17th century Italian luthier Andrea Guarneri and compare their findings with those of micro-invasive analyses to evaluate the merits of the reconstructed volumes and virtual slicing in investigating such layered complex structures (fig. 2).
The team is now ready to scan other varnishes, in order to collect a broader set of case-studies and to go on with disclosing the secrets of the ancient violin-makers.

 

Figure 2.  Radial slices from a cello of Andrea Guarneri; a) The ground layer clogging the porous wood; b) radiopaque particles embedded in the ground layer levelling wood inhomogeneities ; c) dispersion of small particles at the ground-to-varnish interface; d) upper varnish embedding rare radiopaque particles; e) virtual reconstruction of the coating system. Particles dispersed in the ground layer are coloured in blue, and the rare particles visible in the varnish are in red. The ground layer and the varnish layers are evidenced in blue and yellow, respectively. 


 

This research was conducted by the following research team:

Giacomo Fiocco1,2, Tommaso Rovetta1,3, Marco Malagodi1,4, Maurizio Licchelli1, Monica Gulmini2, Gabriele Lanzafame5, Franco Zanini5, Alessandro Lo Giudice6 and Alessandro Re6
 

1 Laboratorio Arvedi di Diagnostica Non Invasiva, CISRiC, Università degli Studi di Pavia, Via Bell’Aspa 3, 26100 Cremona, Italy
2 Dipartimento di Chimica, Università di Torino, Via Pietro Giuria 5, 10125, Torino, Italy
3 Dipartimento di Fisica, Università degli Studi di Pavia, Via Bassi 6, 27100 Pavia, Italy
4 Dipartimento di Musicologia e Beni Culturali, Corso Garibaldi 178, 26100 Cremona, Italy
5 Elettra-Sincrotrone Trieste, S.S. 14 km 163.5 in AREA Science Park, Basovizza, I-34149 Trieste, Italy
6 Dipartimento di Fisica, Università di Torino and INFN, Sezione di Torino, Via Pietro Giuria 1, 10125 Torino, Italy


Contact persons:

Franco Zanini, email: franco.zanini@elettra.eu


Reference

G. Fiocco, T. Rovetta, M. Malagodi, M. Licchelli, M. Gulmini, G. Lanzafame, F. Zanini, A. Lo Giudice, A. Re, "Synchrotron radiation micro-computed tomography for the investigation of finishing treatments in historical bowed string instruments: issues and perspectives", European Physical Journal Plus 133, 525 (2018); DOI 10.1140/epjp/i2018-12366-5

 
Last Updated on Tuesday, 26 March 2019 11:20