Marco Malagodi

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.

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

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.

Handheld XRF and Raman equipment for the in situ investigation of Roman finds in the Villa dei Quintili (Rome, Italy)

In the present work, a variety of fragments of frescoes coming from the Villa dei Quintili in Rome (Italy) and dating back to the II century A.D. were subjected to, first of all, an X-ray fluorescence (XRF) analysis by optimizing a portable spectrometer for non-destructive investigation in the field of cultural heritage. The innovative aspect is the ability to obtain coloured maps referring to the distribution and concentration of elements present in the sample. Other than characterization, the aim was to improve the technique for non-invasive and fast in situ analysis. It has been performed, in conjunction with portable Raman analysis, at the ruins of the Villa dei Quintili on samples of different typologies including pottery, statues and frescoes, dating back to the II/III century A.D., different in colour, support and shape. From the results, the identification of the main pigmenting agents is attempted, providing the group of archaeologists in the villa with extremely valuable information for their work too. In particular, by comparing the XRF results for frescoes analysed in the laboratory, taken from the warehouse of the villa, and XRF and Raman data of frescoes analysed in situ, for which the provenance area inside the villa was known, the context of excavation and the manufacture process for some of the former has been hypothesized.

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.

Surface treatments of wood by chemically modified shellac

Abstract Shellac is an animal resin, which has been widely used as a decorative lacquer for wooden handicrafts in the last centuries. It still finds application as wood sealer and finisher because of its peculiar properties. However, there are also some limitations, such as sensitivity to alcoholic solvents and to pH variations and considerable tendency to chromatic variations upon ageing. The aim of this work is to improve some features of shellac by inducing a cross-linking in its structure. Two new materials were obtained by addition of a polyamine and a polyaziridine to shellac, and their performance were studied by different experiments. The varnish obtained by addition of polyaziridine shows a considerably improved performance when compared to plain shellac. In particular, it preserves almost unaltered the chromatic properties of shellac varnish and it shows an increased resistance to alcohols, to basic agents and to artificial ageing caused by a long lasting UV irradiation.

Pretreatment of alfalfa stems by wood decay fungus Perenniporia meridionalis improves cellulose degradation and minimizes the use of chemicals

Enzymes of wood decay fungi can be exploited to degrade lignocellulosic wastes for sustainable production of bioethanol. Perenniporia meridionalis was tested for growing at different temperatures on stems of alfalfa. The process aims to produce fermentable sugars and can be divided into the following steps: (1) fungal treatment to degrade lignin, (2) microwave pretreatment in water or in phosphoric acid, and (3) enzymatic hydrolysis of cell wall carbohydrates. Thermogravimetric analysis assessed the biomass content of cellulose and lignin after the fungal treatment. Throughout all steps HPLC analysis of sugars, oligomers and by-products (furfural, hydroxymethylfurfural and acids) was performed. Scanning electron microscopy was used for visual inspection and characterization of the experimental material during the treatments. The P. meridionalis pretreatment enhanced the yield of fermentable sugars obtainable by enzymatic hydrolysis in samples subjected to microwave-assisted pretreatment in water, but not in those in acid medium. This is probably related to the very selective removal of lignin by P. meridionalis, exposing cellulose fibers without depleting them. Furthermore, microwave treatment in water produced less byproducts than in acid medium. By exploiting the P. meridionalis lignin degradation is therefore possible to avoid H3PO4 use during the alfalfa stem pre-treatment, reducing economic and environmental impacts.

Provenance study of building and statuary marbles from the Roman archaeological site of Villa dei Quintili (Rome, Italy)

The present work represents the first study addressed to the provenance attribution of marbles from the Villa dei Quintili, an important Roman archaeological site located in the south-eastern area of Rome (Italy). The monumental villa was built in the 2nd century A.D. at the behest of the brothers Sesto Quintilio Condiano and Sesto Quintilio Valerio Massimo. Later (182 A.D.), the Emperor Commodus confiscated the villa, transforming it into an imperial residence until the 3rd century A.D. Different analytical techniques, including polarized optical microscopy, scanning electron microscopy coupled with energy dispersive spectrometry (SEM-EDS), carbon and oxygen stable isotope ratio determinations, inductively coupled plasma mass spectrometry and X-ray diffraction, were used to identify the provenance sources of seventeen white marble samples belonging to statues, covering slabs and architectural elements of the villa. For such a purpose, data obtained were compared with existing databases relative to white marbles commonly used in antiquity collected from historic quarries in the Mediterranean area.Results show that several precious marbles from different Mediterranean sites were used for the statuary as well as for decorative and architectural elements of the Villa thus remarking the importance of the archaeological site.

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.

Structural modification of alfalfa stems during hot water and enzymatic hydrolysis for sugar production

Bioethanol production from non-food lignocellulosic material is one of the most important topics in the field of biofuel production. We report on experiments with a treatment for the production of fermentable sugars from the fibrous parts of alfalfa (Medicago sativa L.), a widely used forage plant. The process is divided into several consecutive steps: ball milling, microwave assisted pretreatment in aqueous medium and enzymatic hydrolysis with a mixture of cellulase and β-glucosidase leading to the final production of fermentable sugars. This process was followed by a detailed HPLC analysis for the detection of sugars, oligomers and by-products, such as furfural, hydroxymethylfurfural and acids. Scanning electron microscopy was used for a visual characterization of the material throughout all these steps. Several plant structures were identified and their successive changes during the different treatment steps were monitored and followed.