Often associated with acts of vandalism, graffiti can also be identified with the so-called street art movement. Moreover, in the historical context of visual arts from the 20th and 21st century, graffiti spray paints feature among the materials employed in the work of representative artists such as Lucio Fontana, Richard Hamilton, Yves Klein, or David Alfaro Siqueiros. In this study, a large number of artist spray paints were analyzed by means of X-Ray Fluorescence (XRF), Fourier Transform Infrared Spectroscopy (FTIR), spectrophotometry, and Hyperspectral Imaging (HSI). The aim of the study was to provide a chemical characterization of the main organic and inorganic components present within the spray paint formulations by means of a complementary nondestructive approach. Titanium white, zinc white, bismuth vanadate yellow, ultramarine, strontium sulfide, iron, and copper oxides, along a series of pigments of the azo, phthalocyanine, and quinacridone classes could be identified. High amounts of barium sulfate as well as calcium-based extenders were also detected. FTIR analysis provided important information regarding the binder composition, mainly modified alkyd resins being identified. Additional information related to the existing chromophores as well as specific binderpigments interactions could also be highlighted within the HSI data sets. Overall results provide new insights on the complex chemistry of this new range of materials, which could help future investigations carried on street art graffiti, contemporary murals, or mixed-media artworks.
<p><strong>Abstract.</strong> In this paper we are presenting our approach and workflow for macro photogrammetry as a complementary method for 3D digitization of polychromies on wood support. Macro photogrammetry can be used for detailed documentation of physical damages in painting layers, underlayers or support. For a better presentation of the context, a selection of typical physical damages, relevant to this study, are explained. Two case studies are presented. Two wooden icons realized with different techniques and presenting different types of physical deterioration. The experiments detailed within this paper represent the first epoch of long-term monitoring of the restoration interventions for each of these icons. All the stage of our workflow is thoroughly detailed with acquisition parameters and processing settings in order to better understand the results and where things can be improved. For each icon a full body photogrammetry process is described, followed by macro photogrammetry on smaller selected areas on the icons' surfaces. Macro magnifications of 1&thinsp;:&thinsp;1 and 2&thinsp;:&thinsp;1 are obtained by using a dedicated macro lens and extension rings. Lighting setups and focus stacking process are also described for a better understanding of the parameters and settings used.</p>
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