A Multi-Analytical Investigation of Roman Frescoes from Rapoltu Mare (Romania)

• Published in: Coatings (Basel) Vol. 12; no. 4; p. 530
• Main Authors: Ion, Rodica-Mariana, Barbu, Marius Gheorghe, Gonciar, Andrei, Vasilievici, Gabriel, Gheboianu, Anca Irina, Slamnoiu-Teodorescu, Sofia, David, Madalina Elena, Iancu, Lorena, Grigorescu, Ramona Marina
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.04.2022
• Subjects: 4th century; Apatite; Archaeology; Beeswax; Calcite; Carbon; Chemical composition; Color; Fourier transforms; Gypsum; Hematite; Mathematical analysis; Morphology; Murals; Optical microscopy; Pigments; Scanning electron microscopy; Spectrum analysis; Thermal analysis; Topography; Wollastonite; X-ray fluorescence; United States > US; Japan; Romania
• ISSN: 2079-6412; 2079-6412
• DOI: 10.3390/coatings12040530

(1) Background: Due to the precarious situation of many monuments or archeological sites, analytical investigations are necessary to obtain information about the used materials, as well as to identify the most appropriate solutions for their conservation/restoration. This paper addresses the characterization of mural painting fragments collected during the excavation in 2018 in Rapoltu Mare (La vie), Deva. (2) Methods: Specific analytical techniques were used, as follows: X-ray diffractometry (XRD), wavelength dispersive X-ray fluorescence (WDXRF), optical microscopy (OM), zoom microscopy and scanning electron microscopy (SEM), spectroscopic techniques (UV–Vis, FTIR, Raman), porosity and thermal analysis, all of which provide information about the structure, chemical composition, morphology and topography of pigments and their deterioration as well. (3) Results: Up to seven different pigments were identified: Egyptian blue, carbon, calcite, gypsum, hematite, goethite and green earth. Egyptian Blue is identified in all the other color areas, except the white area: in the green zone (as degradation product with beeswax) and in the red zone (in mixture with ochre) too. In addition, carbon and beeswax were highlighted as toner and binder for pigments, respectively. In the presence of the organic beeswax binding environment, the Egyptian blue pigment particles darkened or turned yellow significantly, changing the blue to a greenish color. It is also possible to identify wollastonite (CaSiO3) in the blue pigment, which indicates that the temperature used in the manufacturing of Egyptian blue was higher than 950 °C from thermal analysis. The presence of apatite, hematite and gypsum deposits in the Hunedoara region certifies that these pigments could have been of local origin, as demonstrated by the presence of analytically identified elements (Fe, P, S, Ca). (4) Conclusions: The analytical techniques used for such investigations have highlighted the main pigments used in Roman times for various Roman murals.