An in-and-out-the-lab Raman spectroscopy study on street art murals from Reggio Emilia in Italy

Abstract

The street art murals ‘The Big Mother’ by Gola Hundun, the ‘Big Sacral Bird’ by Kenor, the ‘Oriental Carpet” by H101 and “The Economy Subdues You” by Zosen, belonging to the Cooperative Popular Houses of Mancasale and Coviolo in Reggio Emilia (Italy), were investigated by the use of various mobile Raman spectrometers coupled to different lasers and by micro-Raman spectroscopy on selected samples. The study was made necessary by the evident fading of many colours, despite the young age of the paintings, realized in 2010. The first step of the investigation, realized by the on-site campaign, was the identification of the materials, and in particular of the dyes. The main chromophores were identified as polycyclic, monoazo- and disazo- organic pigments, with inorganic compounds as bismuth vanadate (BiVO4) together with the extensive presence of rutile (TiO2). The second step was devoted to the study of the degradation mechanism affecting the colourful layers of the murals. It required the use of laboratory micro-spectrometers and was carried out on a reduced set of samples, selected during the in-situ campaign. This combination of on-site and laboratory Raman spectroscopy allowed the obtaining of the complete identification of the palette used by the different artists in a single day of measurements, in a complete non-destructive day. In addition, it was possible to minimize the number of samples required for the study of the degradation process. Graphical abstract

Interpol questioned documents review 2019–2022

“…Twenty-six articles are included in this section to show the use in forensic document examination of analytical techniques. A selection of these is described below, however the majority are included in reference only [ [344] , [345] , [346] , [347] , [348] , [349] , [350] , [351] , [352] , [353] , [354] , [355] , [356] , [357] , [358] , [359] , [360] , [361] , [362] , [363] , [364] , [365] , [366] , [367] , [368] , [369] , [370] ] as they mainly deal with the analysis of historic documents and their components, although these documents are also examined by the FDE. A further 16 presentations [ [371] , [372] , [373] , [374] , [375] , [376] , [377] , [378] , [379] , [380] , [381] , [382] , [383] , [384] , [385] ] were given at conferences and pertain directly to FDE, as well as the two workshops [ 386 , 387 ] concerning novel analytical techniques in the field.…”

Current progress on murals: distribution, conservation and utilization

“…Non-invasive techniques provide chemical information about the materials, and diagnostic methods can reveal structural information and provide multi-layered structures [ 73 ]. X-ray fluorescence spectrometer (XRF) [ 74 , 75 ], macro X-ray fluorescence (MA-XRF) [ 76 , 77 ], laser-induced breakdown spectroscopy (LIBS) [ 12 , 78 , 79 ], ultraviolet fluorescence [ 80 , 81 ], infrared [ 74 , 82 ], microwave imaging [ 83 – 85 ], Laser Raman Analyzer [ 13 , 50 , 86 ], and Terahertz (THz) spectroscope and imaging techniques [ 84 , 87 , 88 ] were widely used to study the materials of the paintings. For example, the Raman analysis can identify the materials of different pigments.…”

Preliminary approach to protect Street Art from environmental agents and gaseous pollutants

“…According to the literature [6][7][8], the main polymeric binders used are acrylic emulsions, styrene-acrylic emulsions, oil-modified alkyd-based paints, and nitrocellulose resins. These materials have been investigated and studied by various research groups and organizations through morphological, mechanical, chemical, and physical analyzes in order to understand their state-of-art, their chemical composition, and to support conservators and restorers in evaluating the prevention of the degradation of these materials when exposed to different atmospheric conditions.…”