In the present work, a powerful tool for the investigation of paintings is presented. This permits the tuneable multispectral real time imaging between 200 and 5000nm and the simultaneous multispectral acquisition of spectroscopic data from the same region. We propose the term infrared reflectoscopy for tuneable infrared imaging in paintings (Chryssonlakis and Chassery, The Application of Physicochemical Methods of Analysis and Image Processing Techniques to Painted Works of Art, Erasmus Project ICP-88-006-6, Athens, June, 1989) for a technique that is effective especially when the spectroscopic data acquisition is performed between 800 and 1900nm. Elements such as underdrawings, old damage that is not visible to the naked eye, later interventions or overpaintings, hidden signatures, nonvisible inscriptions, and authenticity features can thus be detected with the overlying paint layers becoming successively “transparent” due to the deep infrared penetration. The spectroscopic data are collected from each point of the studied area with a 5nm step through grey level measurement, after adequate infrared reflectance (%R) and curve calibration. The detection limits of the infrared detector as well as the power distribution of the radiation coming out through the micrometer slit assembly of the monochromator in use are also taken into account. Inorganic pigments can thus be identified and their physicochemical properties directly compared to the corresponding infrared images at each wavelength within the optimum region. In order to check its effectiveness, this method was applied on an experimental portable icon of a known stratigraphy.

Modern sustainable architecture indicates the use of local natural stones for building. Greek sandstones from Epirus (Demati, Greece, EN 12440) used as building facades meet aesthetic and have high mechanical properties, but the inevitable interaction between stone materials and natural or anthropogenic weathering factors controls the type, and extent of stone damages. In the present paper, samples of sandstone were treated with a conventional hydrophobic product and four solutions of the same product, enriched with nanosilica of different concentrations. The properties of the treated samples, such as porosity and pore size distribution, microstructure, static contact angle of a water droplet, and durability to deterioration cycles (freeze-thaw) were recorded and conclusions were drawn. The research indicates the increased hydrophobic properties in nanosilica solutions but also the optimum content in nanoparticles that provides hydrophobicity without altering the properties of the stone.

The degradation effects of artificial aging on the “true” pigment color of Byzantine iconography are thoroughly investigated in this work. For this purpose, a multi-material palette is fabricated, consisting of various popular egg-tempera pigments, while the original recipes from the literature are utilized in order to mimic the genuine art of Byzantine painters. Then, artificial aging procedures are appropriately employed to simulate environmental fluctuations in historical buildings, such as churches. A total of four time steps are investigated, including the initial condition, and pigments’ spectra in the ultraviolet/visible (UV/Vis) area are acquired in the diffuse reflectance mode at each individual step. Moreover, a color characterization procedure is realized via the quantification of lightness and saturation by means of the measured UV/Vis spectrum. The main objectives of this work are to determine the color stability, the type of color degradation, and generally the color response through time of the studied pigments. The extracted results indicate that a couple of pigments suffer severe color degradation while the majority present moderate darkening or discoloration.

A main concern for the documentation of artworks (such as paintings, miniatures, icons, manuscripts, wall paintings) is how to reveal the information that stems from the internal paint layers (stratigraphy). This information is up to now mainly acquired through analytical spectroscopic methods which require a micro-sampling operation. In the majority of the cases, the objects under study are extremely valuable, rare and fragile, therefore they may not be subjected to any intervention, rendering the micro sampling procedures prohibitive. The current work proposes a method combining signal processing techniques with novel non-destructive testing techniques for the determination of artworks' paint layers profile in depth as well as the local distribution of the pigments in each of the paint layers without micro-sampling.

The preservation of the Athenian Acropolis monuments constitutes an ongoing top-priority national project of global significance and impact. The project concerning the analytical investigation of the polychromy of the Acropolis monuments presented in this paper was part of the Acropolis Restoration Service (YSMA) program (2011–2015), regarding the restoration of the two corners of the west entablature of the Parthenon, which exhibited severe static damage, and a parallel restoration program of the Propylaea. The scope of this research was to investigate the materials in the paint decoration remains on the monuments by applying, entirely in situ, numerous non-invasive techniques on selected architectural members of the Parthenon and the Propylaea. The research focused, mainly, on surfaces where traces of colour or decoration patterns were visible to the naked eye. Furthermore, surfaces that are referred to in the literature as decorated but that are currently covered with weathering crusts (of white or black colour) and/or layers of patina (of yellowish and orange-brown hue), were also examined. The techniques applied in situ on the Acropolis monuments were X-ray fluorescence, micro-Raman, and Fourier Transform InfraRed (FTIR) spectroscopic techniques, conducted with the use of handheld or portable instruments. The scientific data gathered in situ are discussed in this paper to enhance our knowledge of the architectural polychromy of the classical period. Further investigation by applying analytical techniques on a few selected micro-samples would be highly complementary to this present work.