Tommaso Rovetta

Spectroscopic Analysis to Characterize Finishing Treatments of Ancient Bowed String Instruments

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.

A multidisciplinary materials characterization of a Joannes Marcus viol (16 th century)

BackgroundSeveral musical instruments in the past centuries were decorated with engravings, inlays, or paintings. This paper focuses on an integrated approach to detect and characterize the kind of dyes when used for the decorations. The multi analytical campaign was performed on a viol made by Joannes Marcus in the second half of the 16th century. The instrument has been shattered during World War II, and the fragments are now held in Conservatorio Giuseppe Verdi in Milan; they still conserve the original black and white purflings and the painted decorations. The study is of critical importance since Joannes Marcus worked in the sixteenth century and, in this very period, some executive features were introduced in musical instrument making, which are now veritable standards for this kind of instruments.ResultsAt first, UV fluorescence examination and reflectographic analysis have been performed on the different fragments in order to characterize, respectively, the distribution of varnishes and glues on the surface and to select the areas treated with metal-gall inks that result transparent by long wave IR reflectographic technique. The materials were therefore characterized with X-Ray Fluorescence (EDXRF), Scanning Electron Microscopy with Energy dispersive X-Ray spectroscopy (SEM-EDX) microanalyses and Micro-Infrared Spectroscopy (μFT-IR) techniques. In particular, the metallic elements present in the dyes where revealed through XRF and SEM-EDX, while μFT-IR gave details about organic binders. Elemental compositions obtained for the black decorations allowed to distinguish original parts of the fragments from those restored or remade.ConclusionsThe characterization of materials performed by our multi analytical approach, allowed us to get a deep knowledge of the technology of this ancient viol maker.In particular, the varnishes are probably composed by a diterpenic and/or triterpenic resin. In the same way, in a few traces of glue the presence of proteinaceous substances have been individuated. As for the brush-decorated area, they present a preparation layer rich in feldspars on which a black layer of carbon black particles is applied. On the other hand the purfling areas are colored by an iron-gall dye. In particular the usage of a different ink allowed to identify restored areas.

Automatic Analysis of UV-Induced Fluorescence Imagery of Historical Violins

In recent years, UV-induced fluorescence (UVIFL) photography has proven to be very effective when studying the surface of historical musical instruments, such as violins. This technique makes it possible to highlight superficial details not clearly perceptible with visible light (e.g., retouchings, superficial distribution of varnishes, or wear). The data retrieved are also an important guide for further noninvasive spectroscopic analyses used when the chemical composition of the surface needs to be investigated. However, UVIFL imagery interpretation of a historical violin is no trivial task. In fact, constant playing and the multiple restorations over the centuries have produced very complex surfaces. This work presents an automatic tool designed to facilitate this kind of analysis. Using a quantized histogram in HSV color space, the distribution of the main fluorescence colors on an instrument’s surface can be highlighted, recurrence of the same color in different areas of the same violin can be detected, or different violins can be compared. UVIFL images of seven Stradivarius violins kept in the Museo del Violino in Cremona, Italy, were used as a test set. The results achieved endorse the validity of the proposed approach.

An Interactive Tool for Speed up the Analysis of UV Images of Stradivari Violins

UV fluorescence photography is widely use in the study of artworks, in particular for the analysis of historical musical instruments. This technique allows seeing important details which cannot be observed with visible light, such as retouching, different paints coats or worn areas. The complexity of the interpretation of the surface of a violin is proportional to its state of preservation: more alterations correspond to a more wide range of colors. We designed an interactive tool able to help the scientist to understand the composition of the surface and in particular the distribution of the colors on the entire instrument, avoiding perception illusion. The result is achieved using a quantized histogram in HSV color space. The tests were performed on UV imagery of the Stradivari violins collection stored by “Museo del Violino” in Cremona.

Study of materials and techniques in painted ceiling panels from a palace in Cremona (Italy, 15thcentury)

BackgroundThis study concerns the analysis of four painted wooden panels from the second half of the 15th century which embellish the ceiling of a palace situated in Cremona (Northern Italy). This type of painting was generally used to decorate the top of the walls and the ceilings of the rooms in aristocratic palaces and they usually portray the owner’s ancestors, family members or important visitors. The paintings are of historical importance since they enable us to study the clothing and hair styles which were in fashionable in Italy during the Renaissance. These panels were heavily damaged and required a lot of restoration including the cleaning of the paint layers. This enabled us to carry out a thorough examination of the materials and techniques used for creating these paintings.ResultsVarious micro-samples were taken in order to distinguish the materials and, in particular: (i) to analyze the ground layer and study its function; (ii) to typify the organic binders and the pigments of the polychrome films. The stratigraphic sequence of micro-samples was analyzed using optical microscopy, the elemental composition was determined by means of the SEM-EDX technique while the organic binders were analyzed by means of μFT-IR spectroscopy. The main component of ground layer proved to be clay. The organic binder was probably composed of a protein-based material such as animal glue. This type of ground layer is similar to the traditional 15th century Flemish formula and seems to confirm the strong influence of that artistic technique in Northern Italy. Cross-section investigation showed a primer layer over the ground layer made of white lead pigment. In fact, a white primer was used to cover the ground layer of yellowish clay common in Central Europe. The importance of this research is also confirmed by the study of paint films, for which pigments such as azurite or cinnabar were used. Red lake pigment for painting the subjects’ complexions was emphasized.ConclusionsThe analyses provide new detailed information concerning the materials used for painting the ceiling panels, the layer sequence of the paints and Northern Italian 15th century painting techniques.

Mid and Near-Infrared Reflection Spectral Database of Natural Organic Materials in the Cultural Heritage Field

This study presents mid and near-infrared (7500-375 cm−1) total reflection mode spectra of several natural organic materials used in artworks as binding media, consolidants, adhesives, or protective coatings. A novel approach to describe and interpret reflectance bands as well as calculated absorbance after Kramers-Kronig transformation (KKT) is proposed. Transflection mode spectra have represented a valuable support both to study the distorted reflectance bands and to validate the applicability and usefulness of the KK correction. The aim of this paper is to make available to scientists and conservators a comprehensive infrared reflection spectral database, together with its detailed interpretation, as a tool for the noninvasive identification of proteins, lipids, polysaccharides, and resins by means of portable noncontact FTIR spectrometers.

Alteration processes of pigments exposed to acetic and formic acid vapors

This contribution investigates the chemical modifications experienced by different historic inorganic pigments when exposed to acetic and formic acid vapors naturally produced by wood. The production of acetic and formic acid vapors by wood is well known phenomenon; their interactions with different materials as metals, limestone or glass were already investigated, but only few researches concern interactions with pigments. Pigments modification processes represent one of the most important causes of artworks deterioration since they are directly involved in the pictorial films and their colors. Polychromatic artworks, such as paintings or manuscripts, are generally held indoor where they could be directly exposed to the acid vapors produced by wood floors or cases. In order to study the interactions between pigments and acid vapors, Azurite, Red Lead, Tin-Lead Yellow, and White Lead pigments were selected on the basis of their chemical composition and historical wide use. Powders of these materials were exposed in a simulated acetic and formic acid environments and their alteration processes were investigated by XRD and SEM analyses. The assessment of chromatic variations was performed through a colorimeter.

Microstructural investigations on historical organ pipes

Organs have always been among the most important musical instruments in Europe. Because of their highly complex mechanical systems and the wide variety of materials they are made of, such as metal, ivory, wood or paperboard, they are considered one of the hardest instruments to preserve. Particularly, the different materials used to make the pipes, mainly tin or lead alloys, are sensitive to environmental conditions such as temperature and moisture, and consequent decay. The alteration processes are mostly due to tin-pest development or to the oxidation. As a consequence, sound quality decreases or, in the worst cases, pipes are completely lost. The aim of this work is to investigate several Italian pipe fragments dating from the seventeenth to twentieth century, in order to: (1) analyse the raw materials and the traditional manufacturing of organ pipes, in relation to conservation issues; (2) characterize the particular decay processes; (3) outline a suitable methodological approach to characterize the most common alterations of metal organ pipes. For this purpose, during the analytical campaign, both non-invasive and micro-destructive methodologies were performed, i.e. stereomicroscopy observations, X-ray fluorescence analysis, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis and X-ray diffraction. The application of the proposed analytical procedure allowed the differentiation of the pipe fragments examined into several groups on the basis of original materials and morphological characteristics.