Non-invasive identification of organic materials in historical stringed musical instruments by reflection infrared spectroscopy: a methodological approach

Abstract

The analysis of historical musical instruments is becoming more relevant and the interest is increasingly moving toward the non-invasive reflection FTIR spectroscopy, especially for the analysis of varnishes. In this work, a specific infrared reflectance spectral library of organic compounds was created with the aim of identifying musical instrument materials in a totally non-invasive way. The analyses were carried out on pure organic compounds, as bulk samples and laboratory wooden models, to evaluate the diagnostic reflection mid-infrared (MIR) bands of proteins, polysaccharides, lipids, and resins by comparing reflection spectra before and after the KK correction. This methodological approach was applied to real case studies represented by four Stradivari violins and a Neapolitan mandolin.

Approaches for Detecting Madder Lake in Multi-Layered Coating Systems of Historical Bowed String Instruments

“…Considering the AC binder, the analysis of the dispersed lake particles highlights the characteristic bands of a proteinaceous materials with signals of primary amides (νC=O at 1650 cm −1 ), secondary amides (νNH at 3080 cm −1 ; out-of-phase combination of νCN and δNH 1540 cm −1 ), and tertiary amides (in-phase combination of νC-N and δN-H at 1450 cm −1 ). Focusing on the characteristic bands of the ML, the strong signal at 1095 cm −1 attributed to the sulfate vibration band is predominant, with a slight increase at 1420 cm −1 due to in-plane δ s CH 2 absorption [38] (Figure 8c). …”

Kandinsky’s fragile art: a multidisciplinary investigation of four early reverse glass paintings (1911–1914) by Wassily Kandinsky

“…An unaffected spectrum is given in Fig. 9b, showing intense bands at 1466 and 1753 cm −1 and inverted bands with minima at 2849 and 2916 cm −1 , which classify drying oil properly [7,8,33]. The painting Apokalyptischer Reiter II (1914) reveals several unpainted areas (i.e.…”

“…An example is given in Fig. 8a, showing bands at 1468 (CH 2 scissoring) and 1754 (C=O stretching) cm −1 and inverted spectral features with minima at 2848 and 2915 cm −1 (CH 2 stretching) [7,8,33].…”

A Micro-Tomographic Insight into the Coating Systems of Historical Bowed String Instruments

“…During the last decade, scientists have proposed analytical protocols and procedures dedicated to the identification and characterization of the materials. The musical instruments were tested both through the most common non-invasive spectroscopic techniques [4][5][6][7][8][9], such as X-ray fluorescence (XRF), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR) in ATR and reflection mode, and by micro-invasive analyses, such as micro-FTIR and scanning electron microscopy coupled with energy dispersive x-ray analysis (SEM-EDX) [10][11][12][13][14]. These works allowed scientists to highlight the diversity of the materials used by the ancient violin makers.…”

“…The presence of a multi-layered coating system frequently composed of a very thin proteinaceous preparation, applied directly on the wooden substrate, and an oil-resinous varnish has been detected in several musical instruments manufactured both in Brescia and Cremona. Moreover, some inorganic materials, such as sulfates, carbonates, and silicates [4,8,12,[15][16][17], as well as dispersed colorants [6,13,[18][19][20][21][22], were identified. The characterization of this wide variety of organic and inorganic materials-combined together in order to seal the wood porosity, protect the instrument from moisture and biological agents, and enhance its aesthetic appearance-represents the most challenging task in the investigation of the finishing layers in historic musical instruments.…”