Identification of the finishing technique of an early eighteenth century musical instrument using FTIR spectromicroscopy

Abstract

The study of varnishes from musical instruments presents the difficulty of analysing very thin layers of heterogeneous materials on samples most of which are generally brittle and difficult to prepare. Such study is crucial to the understanding of historical musical instrument varnishing practices since written sources before 1800 are very rare and not precise. Fourier-transform infrared (FTIR) spectroscopy and imaging methods were applied to identify the major chemical components within the build-up of the varnish layers on a cello made by one of the most prominent French violin-makers of the eighteenth century (Jacques Boquay, ca. 1680-1730). Two types of FTIR imaging methods were used: scanning with a synchrotron-based microscope and full-field imaging using a 2D imager with a conventional source. An interpretation of the results obtained from these studies on the Boquay cello is that the maker first applied a proteinaceous layer, probably gelatine-based animal glue. He later applied a second layer based on a mixture of a drying oil and diterpenic resin from Pinaceae sp. From an historical perspective, the results complement previous studies by describing a second technique used for musical instrument finishes at the beginning of the eighteenth century in Europe.

Ageing of resin from Pinus species assessed by infrared spectroscopy

“…Spectroscopic studies performed to date including Pyrolysis coupled to GC/MS (Py-GC/MS) [14][15][16][17][18], Fourier Transform Infrared (FTIR) Spectroscopy [19][20][21][22][23][24][25] and Raman Spectroscopy [26][27][28][29] among other techniques [30] have been focused on the identification of the Pinus resin by determining its characteristic footprints. Nevertheless, a spectroscopic study of the ageing process is expected to give very valuable additional information since, unlike GC/MS, it can detect macromolecules and it doesn't require any sample treatment such as dissolving or derivatization, to identify how molecular species are organized and which reactions or interactions exist among them.…”

Combined approach of FT‐Raman, SERS and IR micro‐ATR spectroscopies to enlighten ancient technologies of painted and varnished works of art

“…IR spectroscopy can be used to get complementary information about the studied materials since it does not generate fluorescence emission. It can be used to characterize binders and minerals in multilayered samples such as painting layers or glazes, or varnish layers using synchrotron radiation . Mathematical developments can also be considered to determine mixtures' components such as first and second derivatives of the spectra, spectral decomposition or principal component analyses …”

Color‐based automatic detection of worn out varnishes on Stradivari's “Scotland University” violin back plate

“…In that case, the user selects a small sample region on the image, then the program extracts the main color features of that area in terms of Hue, Saturation, and Value, and finally all the regions of the surface with a color “close” to the chosen one are automatically highlighted. The procedure can be repeated iteratively until the user has obtained a set of regions of interest, on which apply further not destructive techniques such as X‐ray fluorescence spectroscopy or Fourier transform infrared spectroscopy . The outcome is only a raw classification, it gives information about the recurrence of similar colors and their position on one or more images, but it does not give an interpretation of what they represent.…”