Microanalytical investigation of degradation issues in Byzantine wall paintings

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

“…Their stability to acids is testified upon oxalic acid exposure, which causes only the formation of Ca-oxalates, from the other components of the ochre [32,67]. They are, however, sensitive to high temperatures, such as fires [12,68], or local heating effects related to the use of lasers for cleaning [19,69,70] or for spectroscopical analysis (i.e. Raman spectroscopy, [62,63,71,72]).…”

“…Humidity and chloride ions from various sources cause the formation of black copper oxides (CuO) and green chlorides (nantokite CuCl, paratacamite/atacamite or botallackite Cu 2 Cl(OH) 3 [103,116,[118][119][120][121]). Azurite degrades to black tenorite CuO when exposed to heat in presence of alkali [20,68,91,103,113,114,[121][122][123], while cold alkaline conditions might not affect it [111], or cause conversion to malachite [119], or the formation of tenorite via formation of copper hydroxide Cu(OH) 2 [35,64,114]. On the other hand, it is decomposed by acids, such as oxalic acid to form oxalates (CuC 2 O 4 ·nH 2 O, mooloite) [32,55,116].…”

“…It is soluble in diluted acids (nitric, chloridric, oxalic, acetic), with formation of the corresponding salts, and when heated it transforms to litharge [1,240]. It is sensitive to sulphur containing compounds, as H 2 S and SO 2 of atmospheric or biological origin, and pigments such as arsenic sulphides (As x S y ), vermillion (HgS) and ultramarine (Na 8 [Al 6 Si 6 O 24 ]S n ), especially in manuscripts, wall paintings, and in case the pigment is not mixed with a binder, which cause the formation of dark grey PbS [1,60,93,124,238,241] and of whitish PbSO 4 [59,68,233,242]. This was known to artists and artisans, as demonstrated by the presence of a blank space between yellow orpiment and red lead in a 12th century illuminated manuscript, although mixtures of the two pigments do not behave consistently.…”

Cinnabar alteration in archaeological wall paintings: an experimental and theoretical approach

“…Latin author Vitruvius -writing about Greek and Roman art and architecture during this same period -mentions in his book De Architectura, the application of a wax coating over areas painted with cinnabar to prevent it from darkening (Vitruvius 1960: VII:9). In modern times, cultural heritage professionals at the Roman site of Pompeii, Italy and at other archaeological sites with wall painting pigmented with cinnabar have reported the same phenomenon; red paint layers darken significantly after excavation (Gettens et al 1986, Cotte et al 2006 , egg--tempera and oil--based paint films in fine art paintings (Feller 1967, Gettens et al 1986, Daniels 1987, Spring and Grout 2002, Keune and Boon 2005and Radepont 2013 and Byzantine wall paintings (Pique et al 2007;Kakoulli and Fischer 2009;Sotiropoulou et al 2008, Radepont et al 2011 well as the few studies on archaeological wall paintings (Cotte et al 2006, Cotte and Susini 2009, Radepont et al 2011, Radepont 2013, this paper attempts to further clarify the mechanism(s) of cinnabar alteration in fresco applications, specifically the role of light and chlorine ions, through laboratory--based experiments and thermodynamic modeling. The aim is to understand better the transformations involved as a means to aid conservators in determining what steps may be taken during or immediately following excavation of wall paintings pigmented with cinnabar to slow down, mitigate or avoid the further darkening of the paint layer.…”

Integrated analytical study for the authentication of five Russian icons (XVI–XVII centuries)

“…An integrated multimethod approach using microscopy and spectroscopy is proposed and tested for authenticating these religious paintings on wooden supports (Domenech et al, 1996;Schreiner et al, 2007;Sotiropoulou et al, 2008). Pigments, mineral charges, and metallic leaves were characterized using light microscopy (OM, UV-Vis), scanning electron microscopy coupled with energy-dispersion X-ray spectroscopy (SEM-EDX) and micro-FTIR, whereas the organic components of the paint layers (binders and varnishes) were identified by the specific fluorescence images using UV light microscopy and by Fourier transform infrared spectroscopy.…”