Colour degradation of artworks: an ab initio approach to X-ray, electronic and optical spectroscopy analyses of vermilion photodarkening

Abstract

First principles calculations explain the presence, colour, and photo-reactivity of Hg-containing compounds involved in vermilion degradation.

Degradation of Cd-yellow paints: Ab initio study of native defects in {10.0} surface CdS

“…Hogan et al [20,21] by a first-study based on state-of-the-art electronic structure methods and highresolution microscopic X-ray diffraction clarify the mechanism of undesirable phenomenon of degradation where the bright red pigment vermilion (α-HgS) turns into black color.…”

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

“…Finally, the photodegradation of vermillion was explained in terms of formation of metallic mercury and HgCl 2 , due to the halogen impurities present in the pigment, identified thanks to secondary ion mass spectrometry (SIMS) analysis [207], and to X-ray spectroscopic analysis [208]. The role of Cl-ions, present as an impurity in the pigment, coming from marine aerosol, from the used binder or from pollution, in the degradation of vermillion has been ascertained thanks to the identification of chlorine species [197,199,202,203,[207][208][209]. Calomel (HgCl) 2 was identified by portable and micro-Raman spectroscopy, while HgCl 2 and metacinnabar were not [33,59,73,199].…”

“…Synergy with photodegradation and oxidation [64,66] Involved in discolouration and sulphation [106,197,199,202,203,[207][208][209] Unstable [103,123,200], but still used in wall paintings [73,193,[201][202][203] Red Red lead…”

Zur Photochemie von Künstlerfarben: Strategien zur Verhinderung von Farbveränderungen in Kunstwerken

“…Der n-Halbleiter Zinnoberrot oder Zinnober (a-HgS) ist seit der Jungsteinzeit bekannt und kommt weltweit in verschiedenen Arten von Artefakten vor. [13] Unter der Einwirkung von Licht und Feuchtigkeit chemisorbiert Cl aus der Umwelt auf der a-HgS-Oberfläche.Die Struktur von Cl@HgS begünstigt die Bildung verschiedener Hg-S-Cl-Phasen, die schließlich in das stabilere a-Hg 3 S 2 Cl 2 übergehen. [9,10] Während die Schwarzfärbung von a-HgS früher der photoinduzierten Strukturänderung zu kubischem b-HgS zugeschrieben wurde, [6] bewiesen neuere Analysen von Mikroproben von Kunstgegenständen, [8-10, 11, 12] dass der Prozess mit Hg-Cl-Folgeprodukten wie Hg 3 S 2 Cl 2 -Polymorphen, Hg 2 Cl 2 und HgCl 2 zusammenhängt (Abbildung 1c,d).…”