La diagnostica per la conoscenza storica e artistica delle opere d'arte. Il ruolo delle analisi sui pigmenti nel restauro degli affreschi di Michelangelo nella Cappella Sistina

Il pensiero inerente la tutela delle opere d’arte ha subito una notevole evo- luzione nel corso della storia ed oggi è diventato indispensabile affiancare la scienza della conservazione alle consuete metodologie di restauro. Le scienze applicate ai Beni Culturali coinvolgono studiosi provenienti da diversi campi di ricerca e la collaborazione diventa una prerogativa imprescindibile per il successo dell’intervento conservativo e, soprattutto, per la conoscenza approfondita dell’opera in tutti i suoi aspetti, dai materiali costitutivi alla tecnica di realizzazione. Nell’articolo illustreremo quanto detto soffermandoci tra l’altro sul restauro degli affre- schi di Michelangelo della Cappella Sistina. Questo è stato definito come il primo restauro moderno, proprio perché le analisi hanno accompagnato ogni intervento tecnico sugli affre- schi, i quali sono tornati allo splendore originario nel rispetto dei principi teorici del restauro. In questo e in altri casi la diagnostica è diventata quindi un importante ausilio per lo stu- dio dei Beni Culturali, anche se la scelta della tecnica analitica deve essere relazionata sempre alla domanda alla quale si cerca la risposta. Le scienze applicate permettono di approfondire la storia dell’opera, la tecnica dell’artista, caratterizzano i materiali, ricostruendone le antiche rotte commerciali; tutte queste informazioni permettono di raggiungere una conoscenza senza pari, indispensabile per la valorizzazione, la tutela e la conservazione dei Beni Culturali.he approach to the protection of artwork has considerably evolved through- out history; placing side by side the conservation science and the usual methods of restoration has today become unavoidable. Science Applied to Cultural Heritage involves scholars from different research fields making their collaboration of paramount importance for the success of the conservation process and, above all, for the in-depth knowledge of the artwork in all its aspects, from the constituent materials to the realization technique. This article will discuss this topic taking into particular account the restoration of Michelangelo’s frescoes in the Sistine Chapel. This was defined as the first modern restoration, because scientific tests have accompanied for the first time any technical intervention on the frescoes, which were returned to their original splendor in respect of the theoretical principles of restoration. In this specific case and in other ones, the diagnostics has therefore become an important aid in Cultural Heritage studies, provided that the choice of the analytical technique is always related to the answer that one is trying to pursue. Applied sciences provide an insight into the history of the artworks, the artists’ techniques, the knowledge of employed materials – that allow one to reconstruct the ancient trade routes; all this information can accomplish an unsurpassed knowledge, which is becoming essential for the development, protection and conservation of Cultural Heritage

Electrochemistry for non-electrochemists: a postgraduate formative projec

The essential guidelines are presented of a postgraduate course on electrochemistry for master studies at the University of Valencia (Spain). This course has been designed for students with a minimal knowledge of electrochemistry. It is based on laboratory experiments that, starting from an initial theoretical core, promotes the in-laboratory discussion of concepts, operations, functional relations, etc. The course, although focused on voltammetric techniques, covers the main concepts and experimental aspects of electrochemistry and particular attention is put to erroneous conceptions regarding fundamental physicochemical concepts and operations (misconceptions) as well as on general aspects of the scientific methodology (meta-conceptions) around this discipline

Chemical analysis and computed tomography of metallic inclusions in Roman glass to unveil ancient coloring methods

This paper describes the analysis of two near-spherical metallic inclusions partially incorporated within two Roman raw glass slags in order to elucidate the process that induced their formation and to determine whether their presence was related to ancient glass colouring processes. The theory of metallic scraps or powder being used in Roman times for glass-making and colouring purposes is widely accepted by the archaeological scientific community, although the assumption has been mainly based on oral traditions and documented medieval practices of glass processing. The analysis of the two inclusions, carried out by X-ray computed tomography, electrochemical analyses, and scanning electron microscopy, revealed their material composition, corrosion and internal structure. Results indicate that the two metallic bodies originated when, during the melting phase of glass, metal scraps were added to colour the material: the colloidal metal–glass system reached then a supersaturation condition and the latter ultimately induced metal expulsion and agglomeration. According to the authors’ knowledge, these two inclusions represent the first documented and studied finds directly associated with the ancient practise of adding metallic agents to colour glass, and their analysis provides clear insights into the use of metallic waste in the glass colouring process.This paper describes the analysis of two near-spherical metallic inclusions partially incorporated within two Roman raw glass slags in order to elucidate the process that induced their formation and to determine whether their presence was related to ancient glass colouring processes. The theory of metallic scraps or powder being used in Roman times for glass-making and colouring purposes is widely accepted by the archaeological scientific community, although the assumption has been mainly based on oral traditions and documented medieval practices of glass processing. The analysis of the two inclusions, carried out by X-ray computed tomography, electrochemical analyses, and scanning electron microscopy, revealed their material composition, corrosion and internal structure. Results indicate that the two metallic bodies originated when, during the melting phase of glass, metal scraps were added to colour the material: the colloidal metal-glass system reached then a supersaturation condition and the latter ultimately induced metal expulsion and agglomeration. According to the authors' knowledge, these two inclusions represent the first documented and studied finds directly associated with the ancient practise of adding metallic agents to colour glass, and their analysis provides clear insights into the use of metallic waste in the glass colouring process

Hematite as an Electrocatalytic Marker for the Study of Archaeological Ceramic Clay bodies: A VIMP and SECM Study**

[EN] The electrocatalytic effect exerted by hematite, a ubiquitous component of clay bodies, on the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) can be used to acquire information on archaeological ceramics. The solid-state voltammetric response of different hematite and ochre specimens, accompanied by SECM analysis in contact with 0.10 M HCl aqueous solution, is described. In air-saturated solutions, catalytic effects on the ORR and OER are accompanied by Fe(III)/Fe(II) and Fe(IV)/Fe(III) redox reactions. Such processes are conditioned by a variety of factors, the hydroxylation degree of the mineral surfaces being particularly influential, and exhibit significant variations upon heating the specimens between 300 and 900 degrees C. Voltammetric measurements carried out on a set of archaeological samples of Apulian red-figured pottery dated back within 5(th) and 4(th) centuries BCE permit to obtain site-characteristic voltammetric profiles.The work was carried out within the framework of project PID2020-113022GB-I00 which was financially support by Ministerio de Ciencia e Innovacion and Agencia Estatal de Investigacion (AEI) of the Spanish government.Doménech-Carbó, A.; Giannuzzi, M.; Mangone, A.; Giannossa, LC.; Di Turo, F.; Cofini, E.; Domenech Carbo, MT. (2022). Hematite as an Electrocatalytic Marker for the Study of Archaeological Ceramic Clay bodies: A VIMP and SECM Study**. ChemElectroChem. 9(2):59-68. https://doi.org/10.1002/celc.20210119759689

How Green Possibilities Can Help in a Future Sustainable Conservation of Cultural Heritage in Europe

We are moving towards a future that must be more sustainable in several aspects of society. Culture and cultural heritage have been recognized as indispensable parts of the sustainable growth of society, and the conservation model implemented in Europe has been considered as an example to follow at the economic, environmental, and social levels. The achievement of excellent results and the development of new technologies for the conservation of cultural heritage have highlighted the fundamental need for a method of sustainable conservation. In this commentary paper, we discuss two aspects that can contribute to sustainability in the future of conservation science: the use of innovative chemical products and the monitoring of outdoor sites by means of the forecast of the impact of dangerous factors on artistic surfaces. We are focusing mainly on the material aspect of cultural assets and how hard science can help in sustainable conservation. Even if the concept of sustainability has an ever-growing presence in our society, and different approaches have been given in different fields, it is still difficult to come up with a specific definition that can include the various hues of the world of cultural heritage conservation. The case studies presented in this paper are related to the European area and the advancements made for the sustainable preservation of such heritage. Considering the results obtained from both the chemical and the forecast side, we will try to summarize concisely the tasks that must be achieved in order to indicate as sustainable an approach to diagnostics for cultural heritage, including both the trans-disciplinary features of cultural heritage science and the scientific conservation of materials

Investigations on alloy-burial environment interaction of archaeological bronze coins

This study is focused on ten Roman leaded coins from the archaeological site of the Magna Mater Temple (Rome, Italy). These coins, buried for centuries in a peculiar environment of the archaeological area (i.e., the latrinae), were investigated to explore the chemical composition and microstructure of the inner alloy. The opportunity to examine the core of the alloy permitted to disclose information about the original composition as well as to infer the interaction and the modification of the metal core during burial condition over centuries. Scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and Electron Microprobe Analysis (EMPA) techniques have been employed to study each sample from rim to inner un-corroded core. The results showed that the coins are a Cu-Sn based alloy enriched in Pb. The content of Cu in the Cu-rich area (i.e., the α-phase) is ca 99 wt% and that of the Pb islands (i.e. the β-phase) reaches 97 wt%. The X-ray maps of the interface between the subexternal layer/inner-core revealed the occurrence of high chloride content, in which the distribution of Cl and Pb indicated the presence of lead chloride minerals. SEM-imaging highlighted also a deep corrosion of the patina with cracks and pits. Underneath the corrosion layer, an area of the almost unaltered β-phase composing the bulk material of the coin has been detected

Application of microemulsions for the removal of synthetic resins from paintings on canvas

Traditional cleaning methods with organic solvents often are not suitable for removal of aged resin so researchers have to find new formulations. In this work, a case study is reported in which new microemulsions were applied on the surface of a painting covered by some aged resin layers used during a previous restoration. Based on the quality of the intervention and the analysis of a sample of the varnish carried out with both MALDI-TOF and ATR-IR spectrometers, it was conjectured that this undesired material could be an acrylic polymer. So it was chosen to use xylene, ethyl acetate and propylene carbonate (XYL and EAPC) microemulsions (O/W oil in water). The first is able to solubilise only acrylic polymers, the second may solve both acrylic and vinyl resins. The first has had the greatest effect allowing complete varnish removal and original artwork restoration

PVA hydrogel as polymer electrolyte for electrochemical impedance analysis on archaeological metals

The development of an electrochemical cell based on poly(vinyl alcohol) (PVA) hydrogel as polymer electrolyte for electrochemical impedance spectroscopy analysis (EIS) is discussed. PVA hydrogel is prepared with different cycles of freeze/thawing (F/T) employing distillated and mineral water as solutions. The PVA-disks obtained are compared for their conductivities in order to employ it in an appropriate cell for diagnostic purposes, reducing the invasiveness of the analysis on the sample. The test of the self-consistent disk of PVA is carried out on a modern sample of copper and on an archaeological bronze coin, obtaining an alternative of the classical electrochemical cell for EIS measurements on ancient metals

The application of non-destructive techniques for the study of corrosion patinas of ten Roman silver coins. The case of the medieval Grosso Romanino

This work focuses on the study of ten Grosso Romanino, a silver medieval coin, minted in Rome during the 13th century CE. As the coinage of this denomination occurred during a tumultuous period of the history of Rome, the official documentation from Mint was lost. For this reason, archaeometric investigations were necessary to have an overall knowledge of the Grosso Romanino. This work represents the first attempt of archaeometric study performed on this interesting denomination. The coins were characterized by a combination of non-destructive techniques, i.e., X-ray diffraction (XRD), Scanning Electron Microscopy (SEM-EDAX), micro-Raman spectroscopy and Voltammetry of Microparticles (VIMP), aiming to investigate the external surface and its microstructure and to explore the nature of the alloy and corrosion products. The results show an Ag- rich alloy with minor amount of copper (2.1–3.1 wt%), lead (0.7–3.2 wt%) and other elements. Moreover, the rare corrosion products on the surfaces indicate the presence of a random distributed patina composed by oxides, sulfides and chlorides

New insights on medieval Provisini silver coins by a combination of non-destructive and micro-invasive techniques

The aim of this research was to characterize ten Provisini, one of the most common silver coins in the Middle Age, dating back to the 13th century A.D. These coins are composed by Ag-Cu alloy and were coined in the Roman mint. A non-destructive, micro-destructive and multi-analytical approach was used, aiming to preserve the surfaces of the coins. The results of XRD and micro-Raman spectroscopy allow defining the alloy composition and the mineralogical nature of the alteration products (e.g. cuprite, tenorite, chlorargyrite, stromeyerite). X-ray maps provided information on major elements distribution on the surface. Finally, Electrochemical Impedance Spectroscopy (EIS) and Voltammetry of Immobilized Micro-Particles (VIMP) permitted to reconstruct the possible scheme of the multi-layering of the patina on the coins. Then, the conservation status was monitored