The Case of Musical Instruments
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UNIVERSITA’ DEGLI STUDI DI PARMA DOTTORATO DI RICERCA IN FISICA CICLO XXXIII ADVANCED MULTI-ANALYTICAL METHODS FOR THE STUDY OF MICROSCOPIC LAYERED STRUCTURES: THE CASE OF MUSICAL INSTRUMENTS Coordinatore: Chiar.mo Prof. Stefano Carretta Tutore: Chiar.mo Prof. Danilo Bersani Co-tutore: Chiar.mo Prof. Marco Malagodi Dottorando: Claudia Invernizzi Anni Accademici 2017/2018 – 2019/2020 Rights of use The content of this PhD Thesis, partially based on unpublished research and involving images and data which property is shared among different institutions, can be consulted and quoted in the appropriate forms, but images and whole texts cannot be used if not under the author’s permission, after a proper request (at: [email protected]). To the consciousness Abstract The stratigraphy of historical bowed string musical instruments is a complex and heterogeneous system composed of multiple varnish layers coated on previously treated wood. The entire coating system, collectively called wood finish, is representative of the instrument makers’ working techniques. However, the extended use of the instruments by the musicians as well as the restoration interventions over the centuries could have altered it in terms of layer thickness and composition. Moreover, sampling is rarely feasible because of the need to preserve the value and the integrity of these precious artefacts. In this thesis, we first evaluated potential and limits of a suite of non-invasive spectroscopic and optical imaging techniques in the study of wood finish systems of laboratory mock-ups. Reflection FTIR spectroscopy, XRF, Raman spectroscopy and OCT were applied to the mock-ups by means of portable instrumentation. This non- invasive methodology was supported by SEM-EDX and ATR micro-FTIR analyses. Moreover, the effects of the progressive artificial solar exposure were non-invasively assessed from chemical and chromatic points of view. Then, we explored novel multi- analytical approaches on historical musical instruments by combining the most efficient techniques considered in the experimental study with other advanced non-invasive instrumentation, both non-destructive (NMR-MOUSE, synchrotron radiation micro-CT) and micro-destructive (LIBS), for the characterization of their stratigraphy. Finally, the availability of micrometric samples collected on esteemed instruments represented an extraordinary opportunity to perform analyses by the use of advanced invasive techniques such as the synchrotron radiation FTIR microspectroscopy in reflection geometry. This study involved multiple complementary techniques to obtain high-level information from microscopic layered structures with the final aim of disclosing materials and technologies employed by old violin makers, as well as by restorers and experts in later interventions. Its importance is also related to the preventive conservation of objects that, being played over time and often still nowadays, have undergone different kinds of degradation and wear. Table of contents Table of contents Introduction 0.1 Organization of the dissertation………………………………………………….…..……..... 3 0.2 State of the art on historical bowed string musical instruments……….…. 4 0.2.1 The golden age of the Italian violin making…………………………………. 4 0.2.2 Materials and stratigraphic structure…………………………………………….. 7 0.2.3 Analytical techniques……………………………………………………………………. 10 0.3 Context of the research problem and aims…………………………………….……… 12 0.4 References…………………………………………………………………………………………....…… 14 1. Analytical results on laboratory mock-ups by non-invasive portable instrumentation 1.1 Aims and methods……………………………………………………………………………….…… 23 1.2 Experimental………………………………………………………………………………………….…. 25 1.2.1 Preparation of the mock-ups…………………………………………………………….. 25 1.2.2 Exposure to artificial solar ageing…………………………………………………… 27 1.2.3 Analytical strategy…………………………………………………………………………… 27 1.2.4 Multivariate statistical data analysis………………………………………………… 29 1.3 Results and discussion…………………………………………………………………….………... 30 1.3.1 Optical coherence tomography………………………………………………………… 30 1.3.2 Reflection FTIR spectroscopy…………………………………………………….…… 33 1.3.3 Raman spectroscopy………………………………………………………………………… 38 1.3.4 X-ray fluorescence spectroscopy……………………………………………………... 39 1.3.5 Artificial ageing…………………………………………………………………..………..….. 44 1.4 Conclusions…………………………………………………………………………………..………..….. 49 1.5 References…………………………………………………………………………………………………. 52 2. Innovative applications of advanced non-invasive techniques Preface…………………………………………………………………………………………………………....... 57 2.1 Non-invasive and non-destructive mobile technology to study the stratigraphy of ancient Cremonese violins: OCT, NMR-MOUSE, XRF and reflection FTIR spectroscopy……………………...……………..……………….…..… 59 2.1.1 Introduction……………………………………………………………………………………… 59 Table of contents 2.1.2 Materials…………………………………………………………………………………………... 62 2.1.2.1 Mock-up…………………………………...…………………………………………. 62 2.1.2.2 Historical violins…………………………………..…………………….....…….. 63 2.1.3 Results……………………………………………………………………………………………… 65 2.1.3.1 Optical coherence tomography……………………………………..….…. 65 2.1.3.2 Reflection FTIR spectroscopy……………………………………..….…... 68 2.3.3.3 X-ray fluorescence spectroscopy………………………………..….…… 72 2.3.3.4 Nuclear Magnetic Resonance – Mobile Universal Surface explorer………………………………...………………………………….………….. 73 2.1.4 Discussion………………………………………………………………...…………..………...... 76 2.1.5 Conclusions……………………………………………………………………………………… 80 2.2 A non-invasive and non-destructive micro-tomographic insight into the coating systems of fragments from historical bowed string instruments: synchrotron radiation micro-CT and OCT……………………... 82 2.2.1 Introduction……………………………………………………………………………………… 82 2.2.2 Materials…………………………………………………………………………………………... 84 2.2.3 Results and discussion……………………………………………………………………... 84 2.2.3.1 F01 – Jacobus Stainer…………………………..………………….………….. 85 2.2.3.2 F13 – Gasparo da Salò………………………………………………………… 87 2.2.3.3 F16 – Gasparo da Salò………………………………….……...……………… 89 2.2.3.4 F20 – Giovanni Paolo Maggini………………………………...…………. 91 2.2.3.5 F21 – Lorenzo Guadagnini…………………………......….……………….. 93 2.2.4 Conclusions……………………………………………………………………………………… 96 2.3 Stratigraphic analysis of fragments from historical bowed string instruments and a small violin by combining micro-destructive and non-destructive approaches: LIBS and OCT…………………………………………. 98 2.3.1 Introduction……………………………………………………………………………………… 98 2.3.2 Materials………………………………………………………………………………………....... 101 2.3.2.1 Mock-up……………………………..……………………………………………….. 101 2.3.2.2 Historical musical instruments…………………..………………………... 102 2.3.3 Results and discussion…………………………………………………………………....... 103 2.3.3.1 Mock-up………………………………..…………………………………………….. 104 2.3.3.2 F13 – Gasparo da Salò………………………………..……………….….…… 107 2.3.3.3 F16 – Gasparo da Salò…………………………..……………………….……. 110 2.3.3.4 F20 – Giovanni Paolo Maggini………………..………………………….. 111 2.3.3.5 Bracco 1793 small violin – Lorenzo Storioni……………..…......... 112 2.3.4 Conclusions……………………………………………………………………………………… 114 2.4 References…………………………………………………………………………………………………. 115 3. Innovative applications of advanced invasive techniques 3.1 Discovering the coating structure of ancient bowed string instruments by synchrotron radiation FTIR microspectroscopy in reflection geometry……………………………………………………………………………………………………. 125 Table of contents 3.1.1 Introduction……………………………………………………………………………………… 125 3.1.2 Materials…………………………………………………………………………………………... 128 3.1.3 Univariate and multivariate methodological approaches…………...…….. 128 3.1.4 Results and discussion…………………………………...………...………………………. 130 3.1.4.1 Stratigraphic characterization by morphological, molecular and elemental data………….…………...…………………………………...….. 130 3.1.4.2 SR-FTIR univariate and multivariate imaging………………..…... 136 3.1.5 Conclusions…………………………………………………………………………………….... 140 3.2 References………………………………………………………………………………………………..... 143 Appendices Appendix I – Analytical instrumentation and acquisition parameters……... 151 I. Colorimetry…………...…...…………………………………………………...…………………... 151 II. Fourier transform infrared spectroscopy……………………………………………... 151 II.I Reflection mode…….…………………………………………………………..……... 151 II.II Attenuated total reflection mode……………….…………………..………… 152 II.III Transmission mode……………………….……………………………….……….. 153 III. Laser‐induced breakdown spectroscopy……………………………………………. 153 IV. Nuclear magnetic resonance - mobile universal surface explorer…….. 153 V. Optical coherence tomography………………………………………………………….. 154 VI. Optical microscopy……………………………………………………………………………. 157 VII. Raman spectroscopy………………………………………………………………………….. 157 VIII.Scanning electron microscopy - energy dispersive X-ray spectrometry………………………………………………………………………………………. 158 IX. Stereomicroscopy…………………………………...…………………………………………. 158 X. Synchrotron radiation micro-computed tomography………………………… 158 XI. Ultraviolet-induced fluorescence and visible photography……………….. 159 XII. X-ray fluorescence spectroscopy………………………………………………………. 159 References………………………………………….……………………………………………………… 160 Appendix II – Historical musical instruments…………………………………………….. 163 I. Hämmerle violin 1658, Nicolò Amati…………………………………….…………. 163 II. Hellier violin 1679, Antonio Stradivari…………………………………………….. 166 III. Toscano violin 1690, Antonio Stradivari………………………………….……….. 170 IV. Cremonese violin 1715, Antonio Stradivari……………………………………… 174 V. Principe Doria violin 1734, Giuseppe Guarneri “del Gesù” ……………. 177 VI. Bracco small violin 1793, Lorenzo Storioni……………………………………... 180 VII. Fragments of the “Collezione Sgarabotto” ……………………………………….