Micro-analytical identification of the components of varnishes from South Italian historical musical instruments by PLM, ESEM-EDX, microFTIR, GC-MS, and Py-GC-MS

A multi-analytical investigation was carried out to study varnish micro-samples from historical stringed musical instruments from the collection of the “Vincenzo Bellini” Conservatory in Palermo (Italy). This paper reports on the results of the application of five micro-destructive techniques: optical microscopy analysis of cross-sections, micro-Fourier transform infrared spectroscopy, gas chromatography coupled with mass spectrometry, pyrolysis gas chromatography coupled with mass spectrometry with thermochemolysis, and environmental scanning electron microscopy with X-ray microanalysis. The study provides microchemical information about the composition of the varnishes of the instruments of this collection. The results show that the varnish on all the sampled instruments has a consistent formulation — mainly constituted by a mixture of a tree diterpenoid resin, shellac, and a drying oil. The identification of other organic and inorganic materials is also discussed. It is concluded that the luthiers manufacturing such beautiful instruments did not use any exotic ingredients in the formulations that could be attributed to a secret recipe.