Historical bowed string instruments exhibit acoustic features and aesthetic appeal that are still considered inimitable. These characteristics seem to be in large part determined by the materials used in the ground and varnishing treatments after the assembly of the instrument. These finishing processes were kept secret by the violinmakers and the traditional methods were handed down orally from master craftsmen to apprentices. Today, the methods of the past can represent a secret to be revealed through scientific investigations. The “Cremonese” methods used in the 17th and 18th centuries were lost as the last Great Masters from the Amati, Guarneri, and Stradivari families passed away. In this study, we had the chance of combining noninvasive and microinvasive techniques on six fragments of historical musical instruments. The fragments were detached from different instruments during extraordinary maintenance and restoration treatments, which involved the substitution of severely damaged structural parts like top plates, back plates, or ribs. Therefore, the fragments can offer to the scientists a valuable overview on the materials and techniques used by the violinmakers. The results obtained by portable X-ray fluorescence, optical microscopy, scanning electron microscopy coupled with energy dispersive X-ray spectrometry, and Fourier transform infrared microscopy allowed us to: (1) determine the stratigraphy of six instruments; (2) obtain new information about the materials involved in the finishing processes employed in Cremona; and (3) elucidate the technological relationship among the procedures adopted in the violin making workshops during the considered period.

X-ray fluorescence spectroscopy is a non-destructive technique employed for elemental analysis of a wide range of materials. Its advantages are especially valued in archaeometry, where portable instruments are available. Considering ancient glass, such instruments allow for the detection of some major, minor, and trace elements linked to the deliberate addition of specific components or to impurities in the raw materials of the glass batch. Besides some undoubted advantages, portable XRF (p-XRF) has some limitations that are addressed in this study. The performance assessment of four different p-XRF units and the reconciling of their output were conducted. The results show the limitations in cross-referencing the data obtained from each unit and suggest procedures to overcome the issues. The p-XRF units were tested on the set of Corning reference glasses and on a small set of archaeological glasses with known composition. The compatibility of the output was assessed using multivariate statistical tools. Such a workflow allows us to consider data from multiple sources in the same frame of reference.

Musical instrument coatings are generally made by multi-layered systems of organic and inorganic materials, applied on the wood substrate by the violin makers during the finishing process. This coating has paramount relevance for several aspects: protection from sweat and dirt, increase of specific acoustic features, and especially aesthetic effects. In fact, the colour of historical bowed string instruments represents a very peculiar characteristic of each workshop. Among the various colourants, lakes are the most challenging to detect because of their sensibility to the alteration processes. In this work, non-invasive and micro-invasive procedures were applied to a set of mock-ups mimicking historical coatings systems prior and after artificial ageing, in order to highlight the overall information that can be recovered for the detection of madder lake in historical bowed instruments. A set of techniques, including colourimetry, visible and UV-light imaging, stereomicroscopy, Fibre Optics Diffuse Reflectance spectroscopy (FORS), X-ray Fluorescence spectroscopy (XRF), Scanning Electron Microscopy coupled with Energy-Dispersive X-ray microprobe (SEM-EDX), and Fourier-Transform Infrared spectroscopy (FTIR) were used in order to evaluate the pros and cons in the detection of organic and inorganic component of madder lake at low concentration levels.

Wooden artefacts embrace wide-ranging types of objects, like paintings on panel, sculptures, musical instruments, and furniture. Generally, in the manufacturing process of an artwork, wood is firstly treated with organic and inorganic materials to make it nonporous and morphologically homogeneous, and, at last, the surface treatment consists of varnishes or coatings applied with the aims of conferring aesthetic properties and protecting wood from biological growth and external degradation agents, as well as mechanical damage. In this work, different wooden mock-ups were prepared by varying some parameters: concentration of filler and pigment, respectively, in the ground and paint layers, thickness of the protective varnish coat, and sequence of the layers. The mock-ups were subsequently exposed to time-varying artificial aging processes. The multi-analytical non-invasive approach involved spectroscopic (reflection FT-IR, Raman, and X-ray fluorescence), tomographic (optical coherence tomography) and colorimetric techniques. Data were interpreted using both univariate and multivariate methods. The aim was to evaluate potential and limits of each non-invasive technique into the study of different stratigraphies of wooden artworks. This approach was supported by microscopic observations of cross-sections obtained from selected mock-ups. The methodological approach proposed here would add valuable technical know-how and information about the non-invasive techniques applied to the study of wooden artworks.