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Image spectroscopy (IS) is an important tool for the noninvasive analysis of works of art. It generates a wide sequence of multispectral images from which a reflectance spectrum for each imaged point can be recovered. In addition, digital processing techniques can be employed to divide the images into areas of similar spectral behavior. An IS system designed and developed in our laboratory is described. The methodology used to process the acquired data integrates spectral analysis with statistical image processing: in particular, the potential of principal-component analysis applied in this area is investigated. A selection of the results obtained from a sixteenth-century oil-painted panel by Luca Signorelli is also reported.

Quantitative neutron studies of cultural heritage objects provide access to microscopic, mesoscopic, and macroscopic structures in a nondestructive manner. In this paper we present a neutron diffraction investigation of a Ghiberti Renaissance gilded bronze relief devoted to the measurement of cavities and inhomogeneities in the bulk of the sample, along with the bulk phase composition and residual strain distribution. The quantitative measurements allowed the determination of the re-melting parts extension, as well as improving current knowledge about the manufacturing process. The study provides significant and unique information to conservators and restorators about the history of the relief. [ABSTRACT FROM AUTHOR]

A neutron study on two gilded bronze reliefs by Lorenzo Ghiberti is presented. The two reliefs, representing heads of prophets, come from the north and east doors of the Baptistery of Florence. The east door will be permanently located at the Museo dell’Opera di Santa Maria del Fiore museum at the end of its restoration, which is still in progress at the Metals Conservation Department of the Opificio delle Pietre Dure in Florence. The north door is kept in the original site, on the north facade of the Florentine Baptistery. Both reliefs exhibit critical aspects regarding their state of conservation in particular the stability of the gold layer on the bronze surface. Moreover the east head presents a remelting of which extension and composition are still unknown. The present work describes a non-destructive study of the subgilding area and bulk. The two main objectives of such analyses are: (1) to study the manufacturing technique and state of conservation of the reliefs; and (2) to assess the two cleaning techniques (laser cleaning and Rochelle salts chemical cleaning) used by the conservators during the restoration process of the east door. The experiment was carried out using prompt gamma-ray activation imaging combined with neutron radiography and conventional neutron radiography. The former method was applied to map the elemental composition of the two reliefs, while neutron radiography was used to investigate the bulk. The results provide significant information about subsuperficial areas, elemental composition of the objects from the surface down to a depth of 1 mm below gilding, and bulk structure of the remelting. Such information will guide the curators in the selection of the most suitable microclimatic conditions for the exhibition of the east door and for future conservation work on the north door. [ABSTRACT FROM AUTHOR]

The so‐called Venetian enamelled coppers are a group of objects produced in Italy during the 15th century. Up to now, about 300 objects have been recognized in private collections and in European and US museums. At the end of 19th century, a Venetian origin was suggested, but their provenance is still debated. In this study, the enamel compositions from 22 enamelled copper products from Italian and French collections have been analysed by invasive and non‐invasive techniques. A comparison of the results with Tuscan and Venetian glass databases reinforces the suggestion of a Tuscan (most probably Florentine) origin for these works of art. [ABSTRACT FROM AUTHOR]

The enamels of the Altar of San Giovanni, from the Baptistery of Florence, were investigated using both non-invasive and micro-invasive analysis in order to elucidate the glass melting and colouring techniques. A few fragments detached from the altar and recovered by the restorers were analysed in cross-section by electron probe microanalysis. Moreover, non-invasive investigations by portable XRF allowed a large number of enamelled plaques to be investigated. The results showed a good agreement between the two techniques and made it possible to identify similarities or differences in the enamels of the three manufacturing periods of the altar. [ABSTRACT FROM AUTHOR]

Reports on a study which used image spectroscopy (IS) to analyzed the works of art. Importance of IS; Development of an IS system; Details on the usage of digital processing techniques to divide the images into areas of spectral behavior.

This paper demonstrates that an educated methodology based on both non-invasive and micro invasive techniques in a two-step approach is a powerful tool to characterize the materials and stratigraphies of an Egyptian coffin, which was restored several times. This coffin, belonging to a certain Mesiset, is now located at the Museo Civico Archeologico of Bologna (inventory number MCABo EG 1963). Scholars attributed it to the late 22nd/early 25th dynasty by stylistic comparison. The first step of the diagnostic approach applied imaging techniques on the whole surface in order to select measurements spots and to unveil both original and restored areas. Images and close microscopic examination of the polychrome surface allowed selecting representative areas to be investigated in situ by portable spectroscopic techniques: X-ray Fluorescence (XRF), Fiber Optic Reflectance Spectroscopy (FORS) and Fourier Transform Infrared spectroscopy (FTIR). After the analysis of the results coming from the first step, very few selected samples were taken to clarify the stratigraphy of the polychrome layers. The first step, based on the combination of imaging and spectroscopic techniques in a totally non-invasive modality, is quite unique in the literature on Egyptian coffins and enabled us to reveal many differences in the ground layer’s composition and to identify a remarkable number of pigments in the original and restored areas. This work offered also a chance to check the limitations of the non-invasive approach applied on a complex case, namely the right localization of different materials in the stratigraphy and the identification of binding media. Indeed, to dissolve any remaining doubts on superimposed layers belonging to different interventions, it was necessary to sample few micro-fragments in some selected areas and analyze them prepared as cross-sections. The original ground layer is made of calcite, while the restored areas show the presence of either a mixture of calcite and silicates or a gypsum ground, overlapped by lead white. The original pigments were identified as orpiment, cinnabar and red clay, Egyptian blue and green copper based pigments. Some other pigments, such as white lead, Naples yellow, cerulean blue and azurite were only found in the restored areas. [ABSTRACT FROM AUTHOR]