Nondestructive Raman investigation on wall paintings at Sala Vaccarini in Catania (Sicily)

Abstract

In this work, the results of a Raman campaign for studying seventeenth-century Sicilian frescoes, by using two portable Raman systems, equipped with different excitation sources (785 and 1064 nm), are proposed. The measurements were performed with the aim to provide an in situ diagnostic analysis of the wall paintings (in terms of colorants and preparation layer) and to support the conservators in the framework of the ongoing restoration. The combined use of the two Raman spectrometers has given a complete overview on the artist palette and on the state of preservation of frescoes, also informing us about the technique employed by the painter. Natural pigments as hematite, vermillion, goethite, lead red, lead white and carbon-based black pigments have been identified. Additionally, the application of a transitional RomanesqueRenaissance frescoes method has been noticed by the systematic combined presence of calcite and gypsum in the substrate. Finally, the analyses have highlighted the presence of degradation products, mainly related to alteration of lead-based pigments.

The combined use of SEM-EDX, Raman, ATR-FTIR and visible reflectance techniques for the characterisation of Roman wall painting pigments from Monte d’Oro area (Rome): an insight into red, yellow and pink shades

“…2e, characterised by the aforementioned broad band at 780 cm -1 of calcium hydroxide when excited with near-infrared radiation (Edwards et al 2003) and by the bands at 1085, 711 and 282 cm -1 of calcium carbonate, can be related to the use of the so-called limewash or slaked lime (Edwards et al 1999;Edwards et al 2001;Edwards et al 2003), i.e. a lime-based preparation layer extensively used in Roman wall paintings (Piovesan et al 2011;Crupi et al 2015;Barone et al 2016;Toschi et al 2016).…”

On the stability of mediaeval inorganic pigments: a literature review of the effect of climate, material selection, biological activity, analysis and conservation treatments

“…Lead pigments on ceramic artefacts are sensitive to sulphur containing pollutants, to acidic solutions (rain; CO 2 ; microbial activity), to light and air: anglesite PbSO 4 , cerussite PbCO 3 , hydrocerussite 2PbCO 3 ·Pb(OH) 2 and lead sulphide PbS are formed [166]. Anglesite, attributed to lead pigment degradation was identified on wall paintings as well [214]. To laser irradiation, reduction of the lead compounds (leadwhite, massicot, red lead) occurs on the surface, so that the dark colour is attributed to formation of metallic lead, or Pb 2 O [150].…”