THREE OF A KIND

Reseachers based at Cremona’s Museo del Violino recently had the chance to examine three priceless violins made by Giuseppe Guarneri ‘del Gesu’ in the same year – 1734. Giacomo Fiocco explains the technical methods used to analyse the trio, and what they revealed about the surface materials and design idiosyncrasies

FIGURE 1 The three 1734 violins by Guarneri ‘del Gesù’: the ‘Spagnoletti’, ‘Stauffer’ and ‘Prince Doria’

CISRIC, UNIVERSITY OF PAVIA ALL PHOTOS COURTESY ARVEDI LABORATORY,

FIGURE 2 X-ray fluorescence (XRF) spectroscopy was used in the project

Every musical instrument that came out of the great Cremonese luthiers’ workshops, such as those of Amati, Guarneri and Stradivari, has experienced a different journey. Each one may have passed through the hands of skilled and knowledgeable musicians and collectors – or lain forgotten in an attic for decades. Every violin bears, in some way, the marks of its history and fame that make it unique and inimitable, not only in terms of its acoustic and material features but also in its historical and symbolic ones.

Starting from the 20th century, the great interest in the topic has led makers and scientists to study the violins of the old Italians using a scientific approach, with the aims of characterising the chemical nature of the materials involved in Cremonese finishing treatments, and understand how they affect the instrument’s acoustic properties. Analytical investigations have enabled researchers to obtain a clear picture of the expected materials and their multilayered coatings, consisting of multiple superimposed films of varnishes, generally applied on wood that had been previously treated with a sealer to prevent varnish penetration. The most common materials identified and characterised so far in the coating systems of historical violins are siccative oils, metal-based driers, natural resins, animal glues, inorganic fillers, organic colourants, inorganic pigments, and lake pigments.

Since 2013 the research groups of the Arvedi Laboratory of Non-Invasive Diagnostics of the University of Pavia and the Musical Acoustics Lab of the Politecnico of Milan, both located in Cremona’s Museo del Violino, have been engaged in discovering these unique hidden details and developing new analytical procedures aimed at maximising the information that can be retrieved from priceless historical musical instruments, in order to deepen our knowledge of their materials and acoustical and vibro-mechanical features. These scientific approaches were necessary because in Cremona, traditional manufacturing techniques, materials and recipes (usually transferred orally from master to pupil) were lost in the 19th century at the same time as the closure of the most important workshops in town. This created a deep gulf between historical and contemporary violin making.

THE PROJECT

The laboratories of the University of Pavia and the Politecnico of Milan were fortunate enough to be given privileged access to the collections of the Museo del Violino, including three highly regarded violins made in 1734 by Giuseppe Guarneri ‘del Gesù’ (1698–1744). These were the ‘Spagnoletti’, the ‘Stauffer’ and the ‘Prince Doria’ (figure 1). For this project we used a spectroscopic noninvasive approach, through reflection FTIR and X-Ray fluorescence (XRF) spectroscopies, combined with a 3D model obtained with a 3D laser scanner. XRF (figure 2) and reflection FTIR spectroscopies (figure 3) use different portions of the electromagnetic spectrum – X-rays and infrared respectively – to obtain information on the elemental and molecular composition of the materials, such as the varnish, ground coat, fillers, pigments and polishes. Conversely, the 3D laser scan (figure 4) provides definitive information regarding the construction features of ‘del Gesù’ such as the arching, corners and f-hole shapes, with the aims of obtaining preliminary information about the design peculiarities adopted by Guarneri in 1734. Using these methods, we hoped to observe similarities and differences in the material and design features among the three violins.

All three violins have been played a great deal during their lifetimes. The ‘Spagnoletti’ was for many years the concert instrument of Francesco Diana, leader of the Cremona Opera Orchestra, whose nickname was Spagnoletto (‘little Spaniard’, the name of a popular dance of the time). The instrument came to England via Francesco’s son Paolo, a member of the court orchestra of King George III. Over the next two centuries it went through the hands of a series of owners, both amateurs and professionals, most recently Elliott Golub, concertmaster of the Chicago-based Music of the Baroque, who died in 2019.

The ‘Prince Doria’ was named after the Doria family of Spanish origin, who owned a number of priceless Italian instruments in their time. It has had relatively few owners since the Dorias bought it in 1858; it was sold in 1950 to Leopold Godowsky Jr, son of the Russian pianist. In 1962 it was acquired by the Lionel Perera family for Zvi Zeitlin, then an aspiring young violinist. In a letter from that time, dealer Rembert Wurlitzer wrote that the instrument was unexcelled by any other Guarneri violin known to him, particularly in its tonal quality. Like the ‘Spagnoletti’, the scroll is carved by Giuseppe Guarneri ‘filius Andreae’, father of ‘del Gesù’.

The ‘Stauffer’ has also had a long history of being played. In 1830 the violin belonged to the Italian Bravi Mazzo, and in 1916 it came into the possession of a certain D. Saluzzo. In 1924 it was sold to H.L. Wessel of Copenhagen, and from 1972 to 1977 it was the principal performing instrument of Pinchas Zukerman, who played it in concert halls around the world and on numerous recordings. It has been owned by the Cremonabased Walter Stauffer Foundation since April 1980, and is currently on display at the Museo del Violino.

RESULTS

Our research showed that all three of the 1734 masterpieces analysed in this project showed many similarities, both in their finishing treatments and in their morphological and geometrical features. These were manifested particularly in elements such as their body shapes, the archings, the corners and the f-holes. These peculiarities help to understand the artisanship of Guarneri ‘del Gesù’ more fully.

FIGURE 3 A violin undergoing Reflection Fourier transform infrared (FTIR) spectroscopy

FIGURE 4 A 3D laser scan enabled researchers to analyse the violins’ morphological features

PHOTOS ARVEDI LABORATORY

THE PRESENCE OF CALCIUM SOA P ON THE ‘SPAGNOLETTI’ INDICATES THE USE OF A LUBRICANT

The analytical investigation of the different areas highlighted via UV light (figure 5) showed the presence of a mixture of resins and oil in the varnish on the ‘Prince Doria’, the ‘Spagnoletti’ and the ‘Stauffer’. Some iron-based inorganic phases dispersed in the varnish suggest the presence of red pigments, such as red earth, umber earth and ochres. Lead was probably used as a siccative agent in the oil varnish, as was often the case in oil painting. As regards the ground coat, a proteinaceous treatment, possibly made of casein or animal glue, is widely spread and was identified in particular in some of the areas of the ‘Prince Doria’ and ‘Spagnoletti’ where the wood is exposed, indicating that it is located underneath the varnish layer. In addition, silicate-based compounds such as kaolin, quartz or talc are dispersed in the ground, filling the wood pores. Kaolin and quartz were detected in the ‘Spagnoletti’, whereas in the ‘Prince Doria’ quartz was detected together with a sulphate-based material – possibly gypsum, which was always used as a filler.

Concerning the restoration areas: except for shellac resin, which was detected on all the violins, different materials were highlighted on the surfaces. This indicated different maintenance treatments undertaken during their long history. In particular, the presence of calcium soap on the ‘Spagnoletti’ indicates the use of a lubricant, and the identification of paraffin on the ‘Prince Doria’ and benzoin resin on the ‘Stauffer’ suggest some polishing had taken place. All these materials are commonly used for maintenance practice and as surface polish in restoration.

FIGURE 6 Outlines (a) and cross-sections (b–d) of the ‘Spagnoletti’ (green line), the ‘Stauffer’ (red line) and ‘Prince Doria’ (blue line).

IMAGES COURTESY GIACOMO FIOCCO

The differences in the compositional features and materials described so far are more noticeable than the geometrical and morphological ones. The outlines of the violins studied here are all quite similar, although the largest variation between them appears in the lower left corner (figure 6a). The measurements corresponding to the cross-sections shown in figures 6b–d revealed some slight differences between the violins in the upper and lower right parts.The ‘Prince Doria’ revealed the maximum width in both measurements (upper bouts: 166.02mm; lower bouts: 203.66mm), whereas the other two are significantly smaller: for the ‘Stauffer’, upper bouts are 161.76mm and lower bouts 200.16mm, while the upper bouts of the ‘Spagnoletti’ are 162.38mm and lower bouts 203.42mm. In particular, the ‘Stauffer’ shows significant variations in both the upper and lower parts of the front. The width at the centre is similar for all three.

ARVEDI LABORATORY

Based at Cremona’s Museo del Violino since 2013, the University of Pavia’s Arvedi Laboratory for Non-Invasive Diagnostics represents the confluence of science and the art of violin making.

With the aim of revealing and naming the materials on violins, the Arvedi Lab has optimised the first analytical protocol for the study of stringed musical instruments, using completely noninvasive and non-destructive portable techniques: multispectral imaging with infrared, visible, and ultraviolet light sources to obtain a detailed picture of the violins, and acquire information on the distribution of their surface materials. Stereomicroscopy, enodoscopy and digital high-resolution X-Ray radiography enable the investigation of structural features and the observation of superficial micro-details; while the 3D laser scanner acquires and compares the shapes and volumes of the violins. The two analytical spectroscopic techniques, X-Ray Fluorescence (XRF) and Reflection -Fourier Transform Infrared (R-FTIR) spectroscopy, provide the researchers with accurate chemical information about the materials comprise the stratigraphy.

Thanks to the synergic work with violin makers, restorers and conservators, and the international collaborations with other research groups, the team of chemists and conservation scientists of the Arvedi Lab has analysed around a hundred precious violins from the collections of the Museo del Violino and from private owners, obtaining a surprising amount of knowledge about the manufacturing processes and materials associated with historic and contemporary violin making. Its mission is the sharing of this information about the Cremonese violin making techniques of the past with luthiers, curators, owners, musicians and other stakeholders, by publishing the results in international scientific journals and monographs. Moreover, the Arvedi Lab offers to private owners the opportunity to analyse their instruments to document the materials and their state of preservation.

Photographing a violin at the Arvedi Laboratory for Non-Invasive Diagnostics

A different picture appears when looking at the back plate. Here, the ‘Spagnoletti’ shows the maximum values in the three measurements while the ‘Prince Doria’ and the ‘Stauffer’ revealed slightly smaller values. As for the total lengths of the back plates of the ‘Spagnoletti’, the ‘Stauffer’ and ‘Prince Doria’, they are respectively 349.5mm, 349.37mm and 349.95mm. Those of the fronts are 348.82mm, 349.38mm and 348.81mm. Despite these differences, the creation of the 3D models reveals a good match between the shape of the bodies, suggesting the use of the same mould and templates for all the three violins.

The violins have roughly the same arching profile, except for the central part of the ‘Prince Doria’, which exhibits a higher curvature on the bass side. This is where the bass-bar is located, and it could be due to a poorly fitted bass-bar at some point in the history of the violin, or it might have been a conscious choice by the maker. There are some places on the ribs where they are not perfectly vertical, which is most visible at y = -20mm (figure 6b) on both sides of the ‘Spagnoletti’ and the ‘Prince Doria’, and at y = -230mm on the left side of the ‘Prince Doria’ (figure 6d). The small variations in the relative heights are likely due to twisting of the wood and to the invasive restoration interventions that the instruments have undergone. Some variations can be pointed out comparing the f-holes (figure 7) and the different amounts of wear of the corners on the treble sides of the instruments (figure 8), possibly related to the high concert activity that the violins have undergone, since the effects mainly fall on that side of the violin.

FIGURE 7 F-hole shapes of (a) the ‘Spagnoletti’, (b) the ‘Stauffer’ and (c) the ‘Prince Doria’

FIGURE 7 COURTESY GIACOMO FIOCCO. ARVEDI PHOTO COURTESY MUSEO DEL VIOLINO

FIGURE 8 Outlines of the upper (a) and lower (b) corners of the ‘Spagnoletti’, the ‘Stauffer’ and the ‘Prince Doria’.In both images, the dotted lines represent the left corners while the solid lines represent the right ones.

FIGURE 9 F-hole outlines of (l-r) the ‘Spagnoletti’, the ‘Stauffer’ and the ‘Prince Doria’

The f-holes present the most different features among the three violins in terms of position and dimensions (figure 9).By the measurements obtained through the 3D model, the ‘Spagnoletti’ and the ‘Stauffer’ show a similar length of around 77mm, whereas the ones of the ‘Prince Doria’ are noticeably smaller in the total length (right f-hole: 74.59mm, left f-hole: 75.41mm). In terms of their width at the centre, they present similar values, except for the distance between the two lower eyes of the ‘Stauffer’, where a larger variation between left and right holes is present.

When we integrate and compare the results, it is possible for us to observe how the three coeval violins suffered numerous restorations aimed at maintaining the aesthetics of the finishing treatment. These repeated interventions led to almost total removal or retouching of the original materials in most of the investigated areas. On the contrary, the features relating to the construction techniques of the body remained nearly unchanged.

Sound analysis at the Musical Acoustics Lab

To conclude: the innovative combination of non-invasive spectroscopic techniques and the 3D laser scanner allowed researchers to characterise both the compositional and morphological features, providing detailed information about the finishing layers and past restoration action, as well as disclosing specific aspects of the shapes, morphology and geometries of the violins. The unique opportunity to compare the results of three instruments by the same maker from the same year of production made it possible for us to deepen our knowledge of the manufacturing techniques of Guarneri ‘del Gesù’, and to highlight the extent to which the history of each individual instrument affects materials, and varnishes in particular.

This project was undertaken by the research group of the Arvedi Laboratory of the University of Pavia, the Musical Acoustics Lab of the Politecnico of Milan, and the Museo del Violino in the person of the curator Fausto Cacciatori. The authors thank the Fondazione Museo del Violino Antonio Stradivari for its collaboration, which has contributed to improving this research study. We are grateful to the ‘Friends of Stradivari’ network, and to the owners of the violins for their availability. We would also like to thank the Fondazione Arvedi-Buschini, which supports and funds our research activities

MUSICAL ACOUSTICS LAB

The Musical Acoustics Lab of the Politecnico of Milan is another institution based at the Museo del Violino. It has been active in the area of musical instrument acoustics since 2013. Among its research methods, the Lab works on vibrational analysis, measurement of sound radiation, and timbre analysis and its perception. Over the years the laboratory has developed a strong reputation for expertise in the measurement, analysis and modelling of all the phenomena that contribute to the sound formation from a musical instrument. In particular, Finite and Boundary Element Modelling (FEM and BEM) techniques are customarily used in predicting the impact of geometrical and mechanical modifications on an instrument’s design.

In the past few years the Lab has adopted deep learning techniques for predicting the complex relationships between the geometry of the instrument and its vibrational behaviour, and for measuring the mechanical parameters of the material in a non-invasive way, using vibrational measurements.

During the years the laboratory has developed a strong network of connections with violin makers, associations, and the Cremona Violin Making School. In this context, it has created a prototype platform for vibrational analysis, to be used by makers in their workshop. The laboratory is also available for collaborations with makers for assistance in the design and realisation of their own instruments.Moreover, it is available for supporting museums in noninvasive analyses of collections of musical instruments, and for documenting their state of preservation through non-invasive vibrational measurements.