X-ray Computed Tomography (CT) is a well known diagnostic technique. However, it could be very complex if one wants to use it in fields other than medicine. When CT is applied to large objects, as in cultural heritage, several thousand digital images have to be elaborated, operation that takes a long time. As it is not possible to leave the measurement stage near a monument or in a museum for a long time, it is necessary to develop fast image reconstruction software to allow the experimenters to "look inside" the objects quickly in order to repeat the measurements, if necessary, in a more suitable condition before dismantling the equipment. The X-Ray Imaging Group (University of Bologna) has developed several systems for CT of large objects and, recently, a software, for fast image elaboration, that operates on a network of computers. For illustrating the power of our computing system, this presentation will discuss the CT (done in 2008) of a large Japanese wooden statue (over 200cm of height) of the XIII century, located at the royal palace "La Venaria Reale" (Turin). To investigate the entire statue volume, up to 36 scans were necessary and for each of them 720 radiographs were acquired. To reconstruct all the slices of the complete volume of the object (120 GB) it took 20 days of computing on a good standard PC. The parallelization work was done using the Microsoft (Redmond) HPC cluster and thereafter on a new, transportable, 32 cores cluster at the INFN of Bologna. The HPC environment has proven to be dramatically powerful and easy to use allowing to have the results very quickly. A superlinear speedup of 75 was reached with a 32 cores cluster (the speed up factor, 75, is higher than the number of cores, 32).

The town of Herculaneum was destroyed by the pyroclastic flows of the erupting Mt. Vesuvius in 79CE. However, many artifacts and structures were preserved by this same process, until their rediscovery in the last few centuries. The Villa of the Papyri at Herculaneum contained many papyrus scrolls, carbonized in the eruption but otherwise still intact. Studying the text inside these papyri is made extremely difficult by their fragile state, and any attempts to read them result in irreparable damage. Scholars studying these rolls must painstakingly remove each layer of papyrus to read the text beneath and carefully preserve the resulting fragments. A non-destructive method of unwrapping the Herculaneum papyri would be of great use to scholars, while simultaneously preserving the cultural heritage of one of the greatest archaeological sites in the world. This has been the goal of the EDUCE (Enhanced Digital Unwrapping for Conservation and Exploration) project. In the summer of 2009, our team imaged the interior of two such papyri, housed at the Académie des Inscriptions et Belles-Lettres of the Institut de France in Paris, using X-ray computed tomography. CT provides a non-destructive method to visualize the interior of these scrolls as a three-dimensional volumetric rendering. Only minimal handling of the scrolls was required, to transfer them from archival storage to custom-built sample holders derived from a laser scan of the surface of each scroll. The X-ray scans were captured with a SkyScan 1173 Micro-CT scanner, at resolutions of up to 14 microns. The resulting 3D reconstructions show a tightly compressed, highly chaotic internal structure. Accurate estimates on the length of the scrolls can be made from this data. Manual segmentation of small regions have allowed us to extract single layers. With further refinements of our algorithms, we hope to be able to unroll the entire papyri.

This study concentrates on the analysis of an abstract painting attributed to the Russian avant-garde artist Vasily Kandinsky (1866-1944), often considered as the most important founder of abstract painting. The origin of this painting however is quite obscure and the question was posed if this work could be a copy. Since the occurrence of a modern pigment in a historic painting can point to a copy, a few pigment grains and chips were taken from different colours of the painting, and identified by micro-Raman spectroscopy (?-RS). To avoid sampling of retouched zones, the painting was carefully studied under UVlight and by X-radiography. The X-radiograph revealed a hidden painting, made in a completely different style. ?-RS proved the presence of synthetic organic pigments (SOP's) in the "Kandinsky paint". Although not impossible it is quite rare that SOP's are found prior to 1945. With the aid of an in-house built dedicated Raman reference library containing spectra of approximately 300 different SOP's, most SOP in the painting could be unambiguously identified. Comparing the dates of discovery or of first commercial use of these pigments with the date the painting is supposed to have been made, led to the conclusion that the painting could not have been created by Vasily Kandinsky.

A modern restoration intervention on paintings needs a preliminary investigation of constitutive materials. This investigation is important to take the proper choices before the restoration intervention and it is decisive in order to provide significant research topics. Spectrophotometric analyses have been carried out on "Profeta Stante", a Fifteenth century oil-painted panel, in order to determine artist's colour palette using an absolutely non-invasive method. In accordance with the principle of selective light absorption, which is the basis of spectrophotometry, the result of this analysis are reflectance spectra, the trend of which is typical of each pigment or dye. Then, the particular behaviour of a painted surface to a source emitting the visible wavelength range gives evidence of its nature and it shows how every single pigment is also characterized by the presence of other colour components that confer to it its own hue. Following the false colour infrared (IR-FC) photography outcomes, thirty measurement points, representative of the different colour present in the painting, have been chosen in order to identify the artist's palette and also to evaluate reliability and limits of spectrophotometric and colorimetric analysis when used as preliminary investigation for pigments identification. This work as a whole aims at ensuring an exhaustive pigments comprehension by the combination of the non-invasive techniques which the Centro Conservazione e Restauro "La Venaria Reale" makes use of. The undoubted advantage is to limit the quantity of micro-sampling in accordance with the principle of minimum invasiveness. Following the adopted diagnostic protocol, when the spectrophotometric analysis were found to be insufficient for the pigments' identification, further non-invasive analysis, such as the X-ray fluorescence (XRF), have been used to solve identification problems.

Image Spectroscopy (IS) in the UV-Vis-NIR spectral region is a well-established methodology for the non-invasive diagnostics and documentation of polychrome surfaces. This contribution illustrates a high-performance hyper-spectral scanner, specifically designed for diagnostics on paintings and flat polychrome objects. The system, based on a prism-grating-prism line-spectrograph connected to a silicon CCD camera, operates in the 400-900nm spectral range, with high spectral resolution (about 1 nm) and a spatial sampling of 0.1 mm over areas of about 1 m2. Thanks to these characteristics, this hyper-spectral scanner, recently upgraded with mechanical improvements and a new software interface, still represents a cutting-edge instrumentation for IS applications on polychrome surfaces. This work illustrates the characteristics of the instrumentation and presents review of noticeable results obtained in different cases-.studies.

An ongoing challenge in the analysis of paintings and paint cross-sections is the identification of organic pigments. The focus of this work is the application of fluorescence imaging, fluorescence lifetime imaging and micro- Raman spectroscopy for the characterisation of organic red pigments in easel and wall paintings. Results of the analysis of model samples of a variety of red lake pigments with fluorescence spectroscopy and Raman spectroscopy highlight significant spectral differences for natural red-lake pigments. The in-situ analysis of wall paintings using non-destructive spectrally-resolved fluorescence imaging and fluorescence lifetime imaging techniques has highlighted the presence of red-lake based pigments, some of which are barely visible to the naked eye. However, while fluorescence may provide clear indications of the presence of lake pigments, the identification of original materials on the basis of fluorescence spectra alone is particularly challenging due to the heterogeneity of painting and paint layers and the presence of conservation treatments. Therefore, non-destructive analysis of historical paint cross-sections using environmental Scanning Electron Microscopy (SEM-EDX) and micro-Raman spectroscopy has been performed. Novel applications of micro-Raman spectroscopy coupled with Subtracted Shift Raman Spectroscopy (SSRS) for the subtraction of fluorescence from historical paint cross-sections of highlight that sufficiently well-defined spectra may allow the identification of original materials. The non-destructive analysis of organic historical cross-sections has highlighted the presence of anthraquinone-based organic red dyes bound to an Aluminium-based mordant.

The thermal analysis has been widely applied to the investigation of the structure and of the materials of artworks. Different kind of cultural heritage have been inspected, in particular, by means of the active thermography, a technique based on the analysis of the temperature distribution at the surface of an artifact, evolving as a consequence of a given thermal stimulation. Such a technique enables to detect the presence of sub-surface defects and inhomogeneities and offers several advantages, the main one being its non destructive character. In this work we present an application of the active thermography to the study of a bronze statue. In particular, we refer to a copy of a bronze statue which can be obtained from a single original model using the indirect casting process. The artist's original model is hence preserved by this method and can be used as a reference during the surface finishing and refinement of the casting performed by means of a variety of filing, polishing, and chasing tools. The aim of the present research is in particular to investigate the processing of bronze surfaces, giving the possibility to reveal the cold working hidden under the final polishing.