The exemplary case of a remarkably well-preserved historical musical instrument: the “Tuscan” Stradivari violin (1690)

In recent years, scientific diagnostic analysis has increasingly focused on historical musical instruments, especially bowed stringed ones. The materials composing the stratigraphy of these peculiar works of art are characterized by a complex and heterogeneous nature, which is representative of the working techniques employed by the great violin makers of the past. The entire coating system, so called wood finish [1], includes multiple varnish layers on a previously grounded wooden substrate to prevent varnish penetration. Over the time, however, the original stratigraphy of these centuries-old masterpieces could have been affected by the extended handling during performances and practice, the very close contact of the instrument with the musician skin, or, again, accidents and interventions of maintenance and restoration. As a consequence, variations in its coating thickness and composition have most often occurred. The object of the present study is one of the best-conserved instruments by Antonio Stradivari, namely the “Tuscan” violin (1690) today preserved at the Accademia of Santa Cecilia in Rome (Italy). Commissioned by the Medici family in 1684, as a part of the famous quintet, it is one of the earliest examples of the master’s multiple-layer varnishing method [2]. The remarkably well-preserved wood finish of the violin was non-invasively studied by UV-Induced Fluorescence (UVIFL) photography (by B. Brandmair), Fourier-Transform Infrared (FTIR) reflection spectroscopy and X-Ray Fluorescence (XRF) spectroscopy. The hypothesis drawn from the non-invasive approach was supported by a micro-destructive analysis performed on two micro-samples, one taken from the violin’s top plate (Fig. 1) and the other from the centre bass rib. The micro-samples were analysed by the Optical Microscope (OM) equipped with visible and ultraviolet lights and by the Scanning Electron Microscope (SEM) coupled with Energy Dispersive X-ray (EDX) spectrometer. The aim of the multi-analytical investigation was the characterization of varnishes, pigments and wood treatments constituting the violin’s stratigraphy, trying to understand the methods used by Antonio Stradivari to finish the instrument. From the results, the varnish is confirmed to be applied in a two-layer system: the uppermost salmon-fluorescent coloured varnish (Fig. 1, level A) is oil-resinous composed, with crystals of calcium oxalates witnessing the age of the varnish as a decomposition product of lipid materials [3]; the lowermost yellow-whitish fluorescent layer (Fig. 1, level B) is also characterized by an aged oil-resinous varnish with an aluminium- and oxygen-rich grain dispersed therein which gives rise to possible attributions, including that of alumina (Al2O3) as a substrate for lake pigments [4]. At the interface between the wood and the overlying varnish (Fig. 1, level C), probably related to a wood treatment, a proteinaceous compound can be likely identified as a binder of a few silica and silicates mineral phases. Moreover, rare particles of possible titanium-manganese-iron oxides and/or hydroxides as well as iron-containing aluminosilicates, both suggesting the possible presence of iron-based pigments such as red-ochre or umber earth [5], were found at this level. Under the treatment level, finally, small amounts of chlorine, sulphur, potassium and calcium could be ascribed to a wood pre-treatment method [2]. In conclusion, by combining data from the non-invasive and micro-destructive analytical campaign it was possible to propose a stratigraphic hypothesis of the “Tuscan” violin

“I Cantieri del Suono” project: a public-private cooperation for the valorization of the violin “Piccolo” by Lorenzo Storioni (1793)

The Cultural District of Violin Making is a network of Cremona municipality that keeps the search for quality violinmaking alive and constantly strives to defend traditional craftsmanship. It coordinates various groups in the city involved in education, teaching and research in the field of music and violinmaking. The Bracco Foundation, one of the leading arts patrons in Italy, has chosen to finance the “I Cantieri del Suono” project, dealing with this highly promising area. One of the projects aims consists in the acquisition and valorisation of a rare violin made by Lorenzo Storioni (Cremona, 1744-1816), involving all the main organisations in the District, plus the violin makers that work in the city of Cremona. This small-size violin, known as “Piccolo”, was probably made for a child. The instrument was played in the decades following its construction (1793), but then it has not been used for a significant period. It provides an extraordinary piece of evidence when it comes to construction techniques, the materials used and the composition of varnishes in late eighteenth century Cremona. The analytical protocol developed at the Laboratorio Arvedi di Diagnostica non Invasiva allowed collecting new data on the instrument through a non-invasive approach (XRF and FTIR spectroscopy, X-ray radiography, VIS-UVIFL photography, 3D laser scanning, OCT, NMR). The obtained results were discussed with the students of the Master’s degree in Conservation and Restoration of Cultural Heritage, aiming at identifying the best procedures to preserve the instrument and its materials. Meanwhile, the students of the International School of Violin Making took advantage from 3D model, making a playable copy of the instrument. The violin and its copy will soon enrich the Civic Collections and will be exhibited at the Museo del Violino in Cremona. Up to now different strategies of communications have been put in place (publication of a monography, social network notifications, congress for experts in the field). During the exhibition, attention will be given to the diagnostic results, accompanying visitors through different levels of technical insights

Stradivari's Varnish Revisited: Feature Improvements Using Chemical Modification

The most widespread varnish formulations used by master violin-makers of the "Italian Golden Age", including Antonio Stradivari, were based on mixtures of siccative oils (e.g., linseed oil) and natural resins (e.g., colophony). Similar formulations are still used for the finish of contemporary instruments. Although most precious violins made by Stradivari and other Cremonese Masters are kept in museums, several instruments are still played and their finish may undergo deterioration due to contact with the players. Moreover, the decay of the traditional varnish may occur due to mechanical stress and natural aging caused by environmental agents (e.g., exposure to uncontrolled light, humidity, and temperature changes). The main aim of this research work is to investigate the possible improvement of varnish resistance to the decay induced by different aging processes. For this purpose, the traditional varnish (linseed oil/colophony 3:1 w/w) was recreated in the laboratory following an ancient recipe and then it was functionalized with a cross-linking agent (3-Glycidyloxypropyltrimethoxysilane, GLYMO). Plain and functionalized varnishes underwent artificial aging (UV light, temperature, and humidity variations), and their properties were comparatively studied using different techniques. All the results suggest that the functionalized varnish displays improved resistance to the aging process and particularly enhanced photostability and increased hardness (resistance to scratches)

Discovering the coating structure of historic bowed string instruments: an analytical campaign by SR-FTIR microspectroscopy

In many cases, the possibility to analyze a micro sample from an ancient bowed string instrument allows researchers to collect a wealth of information concerning materials used by the great Masters of violin-making and their construction procedures. In fact, the stratigraphic investigation may provide important information about (i) the treatments of the wood, normally involving proteinaceous materials and inorganic fillers such as carbonates, silicates, sulphates, (ii) composition of the different superimposed layers of varnish, and (iii) organic or inorganic pigments dispersed in the binders of the different superimposed layers of varnish [1]. In the present work, a set of four micro-samples - collected from well-preserved violins made by Antonio Stradivari, Francesco Ruggeri and Lorenzo Storioni - have been mounted in cross section and investigated throughout. The analytical approach has been developed on the embedded samples by means of Synchrotron Radiation (SR) FTIR microspectroscopy in reflection mode using a 15X objective, at the Chemical and Life Sciences branch of SISSI beamline (Elettra - Sincrotrone Trieste) [2]. Data have been collected in the MIR range in correspondence of each single layer of the stratigraphy, setting the lateral resolution in order to match the layer thickness (from few microns to tens of microns). A classification model has been constructed and validated to discriminate classes of materials according to the spectral information [3]. Preliminary results obtained from measurements performed by the micro-invasive SR-FTIR approach are elaborated and discussed, together with the analytical procedures, in order to characterize the features of the different samples

Combining OCT and NMR-MOUSE techniques to study the stratigraphy of historical violins: the thickNESS project

In this work, Optical Coherence Tomography (OCT) and Nuclear Magnetic Resonance (NMR-MOUSE) have been applied to precious historical violins made by the most renowned makers of the Italian lutherie, such as Amati, Stradivari and Guarneri ‘del Gesù’, and hosted in the Museo del Violino in Cremona. Several large fragments removed during past restorations from instruments produced by the luthiers Stainer, Gasparo da Salò, Maggini and Guadagnini, as well as laboratory models simulating musical instruments stratigraphy, were further examined. OCT study was carried out with a prototype high-resolution portable SdOCT instrument providing layer thickness measurements and information about the presence of particles, cracks and delaminations. NMR analyses were performed with a Magritek Kea spectrometer and a Profile NMR-MOUSE (PM5) giving information on the wood density and elasticity, the last one possibly related to adopted treatments. The analyses have been conducted within the MOLAB Transnational Access - EU H2020 Project IPERION CH (thickNESS Project). Data interpretation is still in progress and promising results are expected to reveal in-depth insight into the finishing violin making process. These outcomes will be integrated with the results from UVIFL, FT-IR, Raman and XRF techniques in order to set up a methodology which allowed researchers to non-invasively characterize the stratigraphy of historical violins

From IR to X-rays: approaches to go through the coating system of historical bowed string musical instruments

Some historical bowed string musical instruments produced in Italy from the 16th to 18th Centuries are considered until now peak-quality masterpieces of the violin-making art. Technical skills were mostly lost after the disappearance of the prominent workshops, and nowadays ancient methods and materials are charming secrets to be revealed by scientific techniques. This work discusses the results obtained by investigating the complex coating systems on bowed string instruments produced by four violin-makers, namely: Jacobus Stainer, Gasparo da Salò, Giovanni Paolo Maggini and Lorenzo Guadagnini. They were selected in order to represent convincingly - albeit not exhaustively - the variety of situations that can be encountered when multi-layered coatings on historical bowed string instruments are considered. The coating systems have been investigated though micro-invasive and non-invasive procedures [1], employing UV-imaging, portable X-ray fluorescence, optical microscopy, scanning electron microscopy coupled with energy dispersive X-ray spectrometry and Fourier transform infrared microscopy. In addition, two tomographic techniques (synchrotron radiation micro-computed tomography and optical coherence tomography) have been used to image the finishing layers spread on the wood substrate [2,3]. Chemical investigations and images on cross-sections have been compared with the morphological view obtained by tomography, with particular attention to the ability of the tomographic insight to distinguish and measure the various overlying layers, and to highlight the presence of dispersed particles