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The darkening of cinnabar in sunlight
Abstract
Most cinnabar is brilliant red and remains so under sunlight. However, some cinnabar is photosensitive and irreversibly blackens
during exposure to sunlight. Electron microprobe analyses of cinnabar from several occurrences show that photosensitive cinnabar
contains noteworthy concentrations of chlorine, whereas non-photosensitive cinnabar does not. Experimental evidence shows
that non-photosensitive cinnabar becomes photosensitive after exposure to halogens. The darkening of cinnabar in sunlight
is caused by the presence of contained chlorine or other halogens.
... Cinnabar is a notoriously photosensitive mineral, irreversibly blackening upon light exposure. Several localities have been identified that produce photosensitive specimens (Dreyer 1939;McCormack 2000). At these locations, cinnabar is associated with various mercury halide minerals (McCormack 2000;Neiman, Balonis, and Kakoulli 2015) and often contains trace amounts (∼1 wt%) of alkali halogens, usually chlorides (Dreyer 1939;McCormack 2000;Keune and Boon 2005). ...
... Several localities have been identified that produce photosensitive specimens (Dreyer 1939;McCormack 2000). At these locations, cinnabar is associated with various mercury halide minerals (McCormack 2000;Neiman, Balonis, and Kakoulli 2015) and often contains trace amounts (∼1 wt%) of alkali halogens, usually chlorides (Dreyer 1939;McCormack 2000;Keune and Boon 2005). At these concentrations, halogens are integral catalysts for the photochemical redox reaction which produces the blackening (Keune and Boon 2005;Anaf, Janssens, and De Wael 2013;Neiman, Balonis, and Kakoulli 2015). ...
... Several localities have been identified that produce photosensitive specimens (Dreyer 1939;McCormack 2000). At these locations, cinnabar is associated with various mercury halide minerals (McCormack 2000;Neiman, Balonis, and Kakoulli 2015) and often contains trace amounts (∼1 wt%) of alkali halogens, usually chlorides (Dreyer 1939;McCormack 2000;Keune and Boon 2005). At these concentrations, halogens are integral catalysts for the photochemical redox reaction which produces the blackening (Keune and Boon 2005;Anaf, Janssens, and De Wael 2013;Neiman, Balonis, and Kakoulli 2015). ...
Damage and susceptibility are key concepts in conservation but are rarely explicitly defined. This paper provides definitions for these terms and applies them to mineral collections. Minerals are often overlooked in the context of heritage conservation due to their assumed stability. While many appear to be stable under ambient conditions, at least 10% of known mineral species are susceptible to temperature, moisture, light, or pollutant levels common in museum stores and displays. These susceptible minerals are represented in museums as natural history specimens (as crystals and inclusions within rocks and fossils), pigments in paintings, and deterioration products of other minerals, metals, and many other object types. A new online resource, the Mineral Susceptibility Database, has been designed to facilitate the preservation of minerals by providing relevant information in a single, accessible location. Data were collated and synthesised from various fields of research, many of which are not easily accessible to museum professionals. As an open repository of interdisciplinary research, the Mineral Susceptibility Database encourages informed decision-making and advocates cross-disciplinary communication, both of which are necessary to improve the care of mineral and geological materials.
... However, although the Raman ; Fig. 4), the presence of Fe and occasionally of Pb (Supplementary Table 2) could suggests that cinnabar was mixed with other pigments [19,22,23]. In fact, cinnabar was an expensive pigment often used as an admixture with the cheaper and more readily available haematite or red lead, presumably both to extend it and to brighten the other red pigments (e.g., [21,24,25]). It is worth noting that on the right sight of the lateral depiction, in correspondence of the bright red band below the entablature (Fig. 2), the colour appears Table 3). ...
... Spectroscopic data revealed that it was obtained by using a different pigment, composed of iron oxide compounds. The narrow doublet at ca. 225 and 290 cm −1 and the peaks at ca. 413, 498 and 616 cm −1 (Table 1) [19,23], in fact, feature hematite, the iron oxide representing the principal colouring component of red ochres, a pigment mainly used for red decorations in the Roman period (e.g., [21,25,32,33]. In the parts of the wall painting where dark red decoration overlying the bright red ones, a* and b* values appear higher ( Fig. 6; Supplementary Table 3) and pXRF detected Hg (Table 1). ...
During the Roman age, the southern promontory of the gulf of Baia was the perfect location for the construction of villae maritimae for the Roman élite that decided to spend their summer residences by the sea.
One of these residences is now located in the military fortress of the Castello Aragonese di Baia, built in 1495 CE during the Aragonese period (15th century). Here, during restoration works, the ruins of the residential sector of the villa, which historical sources ascribe to Caesar, were unearthed. The most representative evidence of this is the outstanding in situ remain of mosaics, decorated plasters and finely frescoed surfaces decorated according to the repertoire of the II style. This research aims to investigate the polychromy of a wall decoration representing a perspective depiction of architectural scenes en trompe l'oeil analysed by means of a multi-analytical, non-destructive approach performed in situ. The combined use of spectroscopic techniques (portable X-ray fluorescence, Raman and Fourier Transform Infrared Spectroscopy) points out the use of a characteristic Roman palette, quantitatively assessed by colorimetric measurements. It consists of red and yellow ochre, calcite, hematite, organic black pigments, precious materials such as cinnabar and Egyptian blue, green copper compounds. Fourier Transform Infrared Spectroscopy also revealed the presence of synthetic resins, likely used for the conservation of mural paintings. These are, however, damaged by atmospheric humidity, as detected by Infrared Thermography. Gypsum has been identified as the main weathering product.
... Although cinnabar is generally considered resistant, darkening of paints containing this pigment is common. Different possible pathways for the darkening of cinnabar during light exposure have been considered: (i) formation of black metacinnabar (β-HgS) [39,40], (ii) formation of a thin layer of black colloidal mercury (Hg) [41], (iii) formation of metallic mercury (Hg) due to the intervention of chlorides, either as a catalyst in the redox reaction of cinnabar or as intermediate reaction products that are subsequently photochemically reduced [42][43][44], and (iv) in the absence of chlorides, reduction to metallic mercury (Hg) via photo-induced electron transfer when cinnabar pigments are exposed to UV-C at room temperature and high relative humidity [45]. Moreover, in the absence of light, transformation of αto β-HgS can be induced by temperatures higher than 350 • C [46][47][48][49][50]. ...
... In the CIN-C-R, the colour changes were determined by salt precipitation and degradation in the binder (i.e., formation of fissures in both binders), although darkening was also observed in isolated areas. Different possible pathways for blackening have been proposed [39][40][41][42][43][44][45]. In the present study, it is possible that the chloride (15.8 mg/L Cl − ) present in the water of the climatic chamber and detected in all the aged paints (HE and CIN), was involved in darkening of some of the CIN-based paints. ...
Hematite-and cinnabar-based paint mock-ups prepared with either rabbit glue or egg yolk binder were artificially aged in an SO2-rich atmosphere, as a model system for investigating the deterioration of tempera paints exposed to an industrial atmosphere. The overall research aim was to identify the type of degradation occurring in tempera paints and the different alteration mechanisms related to the physical, mineralogical and chemical characteristics of the paint. Tempera mock-ups were prepared by mixing binder (egg yolk or rabbit glue) and pigment (cinnabar of different particle sizes or hematite) and were then exposed to SO2 for 2 months in accelerated aging tests. The colour, gloss, reflectance, roughness and micro-texture of the surfaces of the mock-ups were determined before and after the tests. In addition, chemical and mineralogical changes were determined by X-ray Powder Diffraction (XRPD), Attenuated Total Reflection-Fourier Transform Infrared spectroscopy (ATR-FTIR) and Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS) analysis. Colorimetric changes were confirmed, mainly in the cinnabar-based paints containing egg yolk, and in the hematite-based paints containing rabbit glue. Neoformed mineral phases have not been detected by XRPD, but precipitation of gypsum on the exposed surfaces has been confirmed by SEM. For cinnabar-based paints, the amount of sulfate-rich deposits was higher on egg yolk mock-ups than on rabbit glue samples, though the opposite was observed for the hematite-based paints. This confirmed the influence of the binder composition and pigment-binder tandem in the susceptibility to SO2 deposition. Pigment particle size did not have a clear influence on the physical and chemical changes in the tempera mock-ups during the ageing tests.
... Different mechanisms responsible for the darkening have been proposed: a) transformation of red hexagonal α-cinnabar into black metacinnabar [8,9], a theory which has been questioned more recently [3,10,11]; b) formation of an alteration layer containing mercury chlorides and/or mercury sulfochlorides [3,7,10,12]; and c) photochemical redox reaction of HgS into Hg 0 and S 0 , catalyzed by halogens at high RH and sunlight/UV exposure [13,14]. A number of researchers [10,[15][16][17][18] suggest that the cinnabar's observed photosensitivity would depend on the pigment's preparation process/chemical composition and that impurities would trigger darkening under light exposure. In the vast majority of studies the critical role of halogens in the blackening of cinnabar is highlighted based on the presence of chlorine compounds (i.e., calomel, terlinguaite, eglestonite, corderoite, and kenhsuite) detected in the pigments´alteration layer, which are often considered as intermediate products of the chlorine-induced degradation of cinnabar [3,7,11,14,19,20]. ...
... Several studies suggest that the photo-induced darkening is produced by the formation of an amorphous phase [10], possibly metallic mercury and that halogens would act as catalysts in this reaction [11,12,14,18]. Dreyer [15], in a pioneering study, also proposed that a layer of colloidal mercury would be responsible for the blackening of cinnabar. More recently, Anaf et al. [13] were able to demonstrate the formation of metallic mercury and the simultaneous release of SO 4 2− on laser-exposed, electrochemically treated (pretreatment in 1 M NaCl solution) HgS/Pt electrodes. ...
The darkening process of cinnabar and vermilion-based paint surfaces as well as pigment-binder interactions upon weathering have been studied by subjecting egg-yolk tempera dosimeters to UV-aging, RH cycling, and 2-year outdoor weathering with and without direct exposure to rain and sunlight. X-ray photoelectron spectroscopy proved that photooxidation resulted in Hg enrichment in the cinnabar pigment surface of weathered paints exposed to direct sunlight and rain, which caused important binder loss as well as thermal-induced crack formation and severe darkening of the unprotected pigments. Remarkably, darkening occurred in the absence of halogens and all pigments, independent of their preparation process (ground minerals or synthesis by a wet-process), were affected. After UV-aging, RH-cycling, and outdoor weathering in the absence of direct sunlight and rain, in contrast, pigments were still covered by egg yolk and did not undergo significant alteration. The binder, however, suffered important conformational and physical changes, including crack formation. These changes were significantly influenced by the size of the pigment. Additionally, XRD results indicate the presence of metacinnabar as an impurity in the original cinnabar and vermilion pigments, which might have been mistakenly identified as an alteration product in previous studies.
... Sunlight irradiation is able to induce the chemical transformation of a-HgS (McCormack, 2000;Radepont et al., 2011;Radepont et al., 2015) and b-HgS (Hsieh et al., 1991) in the solid phase or in a HgS(s)-water interface; this transformation can be further enhanced in the presence of Cl - (McCormack, 2000;Radepont et al., 2011;Radepont et al., 2015), with calomel (Hg 2 Cl 2 ), cordierite (a-Hg 3 S 2 Cl 2 ), kenhsuite (g-Hg 3 S 2 Cl 2 ), or dissolved Hg 2C as products (Hsieh et al., 1991;Radepont et al., 2011). In addition, upon irradiation with visible light, the vaporization of Hg 0 from a-HgS (Anaf et al., 2013) or b-HgS (Hsieh et al., 1991) was observed, suggesting there is a photochemical reduction of HgS. ...
... Sunlight irradiation is able to induce the chemical transformation of a-HgS (McCormack, 2000;Radepont et al., 2011;Radepont et al., 2015) and b-HgS (Hsieh et al., 1991) in the solid phase or in a HgS(s)-water interface; this transformation can be further enhanced in the presence of Cl - (McCormack, 2000;Radepont et al., 2011;Radepont et al., 2015), with calomel (Hg 2 Cl 2 ), cordierite (a-Hg 3 S 2 Cl 2 ), kenhsuite (g-Hg 3 S 2 Cl 2 ), or dissolved Hg 2C as products (Hsieh et al., 1991;Radepont et al., 2011). In addition, upon irradiation with visible light, the vaporization of Hg 0 from a-HgS (Anaf et al., 2013) or b-HgS (Hsieh et al., 1991) was observed, suggesting there is a photochemical reduction of HgS. ...
Mercury sulfide (HgS, cinnabar, and metacinnabar) is a major Hg sink, widely available in various environmental compartments. The formation and dissolution of HgS play a crucial role in the geochemical cycle of Hg, including its transport, reduction, methylation, and toxicity. Unlike other Hg species (e.g., methylmercury, Hg⁰), environmental HgS occurs in the form of different sized particles, leading to various challenges regarding its quantification and the evaluation of potential environmental impacts. This review summarizes the current analytical methods for the identification, characterization, and quantification of HgS, including sequential chemical extraction, X-ray absorption spectroscopy, programmed thermal desorption, and selective vapor generation, among other methods. In addition, the chemical/biological pathways and mechanisms involved in the formation and dissolution of HgS are reviewed, as are the analytical and environmental perspectives of HgS. This review furthers our understanding and encourages the study of the environmental formation and dissolution of HgS and its role in the geochemical cycle of Hg.
... The substance retains the original red pigment colour, although it has taken on a darker hue in some areas. Cinnabar is an unstable pigment in the long term and can turn black when exposed to light (Çamurcuoglu, 2015;McCormack, 2000) or due to its long stay under water (Béarat et al., 2013). The latter seems the most likely reason given the particularity of the context of discovery. ...
Numerous researchers point out the emergence of human symbolism is related to the evolution of the complexity of human cognition. Red mineral pigments have been used extensively, particularly with anatomically modern humans, for various purposes. However, the management and supply of these pigments during prehistoric periods remains poorly investigated. Still today, the limited application of physico-chemical analyses often leads to a simplistic attribution of these pigments as ochre. The studies of data from recent literature presented in our paper show a progressive introduction and exploitation of cinnabar ore, to achieve a red pigment, from the seventh millennium BC. In this panorama, the new data obtained from the analyses of samples of artefacts from La Marmotta (Italy) show a wide use of cinnabar in central Italy from the early Neolithic and attest to the earliest use of this ore in the western Mediterranean area.
... In some illuminations where vermilion was identified, chromatic changes (blackening) were observed, which have been related to the photosensitivity of the pigment when it is agglutinated with tempera [53]. Hypotheses about the mechanisms responsible for this pathology have been proposed; however, the experimental data were not consistent with the observed chromatic variation [54][55][56][57][58][59]. In recent years Elert and Cardell (2019) were able to demonstrate that the darkening is a product of a thin layer of metallic mercury deposited on the surface of the pigment resulting from direct exposure to sunlight and humidity [60]. ...
Choirbooks are historical heritage manuscripts used for the performance of vocal music in religious ceremonies in colonial times. This study aimed to understand the characteristics of choirbook manuscripts produced in the Real Audiencia de Quito during the 17th century. The methodology combined non-invasive techniques, such as infrared false-color imaging (IRFC) and X-ray fluorescence (XRF), together with spot analysis by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) and Fourier transform infrared spectroscopy with attenuated total reflection (FTIR-ATR). The analytical results revealed the use of pumice, chalk and lime carbonate as support materials in the manufacturing process and surface treatment of the parchment. In the illuminations, three pictorial techniques based on protein, polysaccharide and lipid binders were recognized, establishing that the pigments used with greater regularity in the illuminations were vermilion, minium, verdigris, orpiment, azurite, and indigo, preferably in a pure state. Materials used less regularly were also identified, such as yellow ochre, saffron, smalt, red ochre, and bone black, among others. Regarding the vulnerability of the pictorial materials, it was determined that, although most of the pigments exhibit chemical stability, they present some vulnerabilities associated with their intrinsic composition and the medium that contains them.
... The substance retains the original red pigment colour, although it has taken on a darker hue in some areas. Cinnabar is an unstable pigment in the long term and can turn black when exposed to light (Çamurcuoglu, 2015;McCormack, 2000) or due to its long stay under water (Béarat et al., 2013). The latter seems the most likely reason given the particularity of the context of discovery. ...
... It is of great significance to discuss the alteration mechanism. Dreyer [36] suggested that alkali (KOH in his experiment) promotes αHgS darkening. Halides such as chloride were widely considered as a reason for αHgS to βHgS transformation as catalytic elements [37][38][39][40]. ...
Jade is most valued in Chinese culture since ancient times. For unearthed jade artifacts, the alteration color resulting from weathering effects and human activities provides information for cultural heritage conservation, archaeology, and history. Currently, the noninvasive 3-dimensional characterization of jade artifacts with high chemical and spatial resolution remains challenging. In this work, we applied femtosecond pump–probe microscopy and second harmonic generation microscopy techniques to study the black alteration of an ancient jade artifact of the late Spring and Autumn period (546 to 476 BC). The direct cause of the “mercury alteration” phenomena was discovered to be the conversion of metacinnabar from buried cinnabar in the tomb. Furthermore, a 3-dimensional optical reconstruction of the black alteration was achieved, providing a high-resolution method for analyzing the blackening mechanism without the need of sample damage. Our approach opens up new opportunities to extract microscopic spatiochemical information for a broad range of alteration colors in jade artifacts.
... The detection of well-resolved, intense X-ray energy lines of Hg, associated with weak lines of S, by pXRF on darkened areas revealed the consistent presence of mercury sulfide, most likely a combination of cinnabar and metacinnabar (β-HgS) [32][33][34][35][36][37]. ...
Polychromy in Ancient Greek Sculpture was the subject of the exhibition Chroma: Ancient Greek Sculpture in Color, held at The Metropolitan Museum of Art (The Met), New York, in 2022–2023. On this occasion, a multidisciplinary project involving The Met’s Departments of Greek and Roman Art, Objects Conservation, Imaging, Scientific Research, and colleagues from the Liebieghaus Polychromy Research Project in Frankfurt, Germany, was carried out to study an Attic funerary monument. The color decoration of the sphinx was reconstructed by combining non-invasive and minimally invasive techniques that provided information about surviving and lost pigments, original design, and painting technique. Results of multiband imaging, digital microscopy, and X-ray fluorescence spectroscopy guided the removal of minute samples from selected areas for examination by Raman spectroscopy and scanning electron microscopy, coupled with energy-dispersive X-ray spectroscopy, to shed light on the pigments and paint stratigraphy. The color palette included two varieties of blue, Egyptian blue and azurite, a carbon-based black pigment, two reds, cinnabar and red ocher, and yellow ocher, all painted directly over the marble without a preparation layer. The scientific findings informed the physical reconstruction of the sphinx made by archaeologists from the Liebieghaus Polychromy Research Project, featured in the exhibition.
... ruros(Keune y Boon, 2005;McCormack, 2000;Radepont et al., 2015;Spring y Grout, 2002) o a la presencia de un coloide de mercurio metálico superficial(Dreyer, 1939), detectado en probetas sintéticas de témpera envejecidas(Elert y Cardell, 2019). En un trabajo sobre las pinturas murales romanas de la Villa Sora del área vesubiana se incide en la sulfatación del carbonato de calcio como factor que contribuye al ennegrecimiento de la capa pictórica(Cotte et al., 2006), debido al material particulado atrapado en la estructura porosa del yeso. ...
Within the research project entitled Evaluación de tratamientos de limpieza para la eliminación de depósitos calcáreos en cerámicas arqueológicas, a new methodology for the evaluation fo the efficacy and safety os several cleaning treatments for archaeological pottery has been developed, by including diverse techniques from applied sciences.
... La hipótesis tradicional (Feller, 1967;Liberti, 1950Liberti, , 1951 atribuía el ennegrecimiento del pigmento a la conversión de α-HgS rojo en β-HgS, metacinabrio negro, a una temperatura de 345 ºC (Dickson y Tunnel, 1959). Sin embargo, son escasos los ejemplos en los que se ha detectado esta fase en zonas ennegrecidas (Istudor et al., 2007;Yu, Warren, y Fischer, 2019) y resultan abundantes las referencias recientes que apuntan a una fotodegradación asistida por clo-ruros (Keune y Boon, 2005;McCormack, 2000;Radepont et al., 2015;Spring y Grout, 2002) o a la presencia de un coloide de mercurio metálico superficial (Dreyer, 1939), detectado en probetas sintéticas de témpera envejecidas (Elert y Cardell, 2019). En un trabajo sobre las pinturas murales romanas de la Villa Sora del área vesubiana se incide en la sulfatación del carbonato de calcio como factor que contribuye al ennegrecimiento de la capa pictórica (Cotte et al., 2006), debido al material particulado atrapado en la estructura porosa del yeso. ...
The aim of this article is to present the latest research outcomes of the APUV project(Analytica Pompeiana Universitatis Vasconicae) regarding the transformation of pigments employed on mural paintings of the Archaeological Park of Pompeii (Italy). More concretely, the results concerning red ochre and red cinnabar darkening and the in situ discrimination between original red
ochre and dehydrated yellow ochre due to the thermal effect of the 79 AD Mount Vesuvius eruption and its transformation extent according to the specific temperature impact are addressed.
... The transformation of red trigonal α-HgS into black cubic β-HgS metacinnabar, which is reported to take place at 344 ± 2°C [6,7], was assumed at the beginning of the twentieth century and proposed by Eibner and Liberti, among many other authors [8,9]. More recently, other theories have gained increasing attention, such as the photosensitization of cinnabar induced by chlorides or the reduction of Hg (2) to black Hg(0) [10][11][12][13]. Indeed, to the best of our knowledge, the main attributions of metacinnabar as the compound present a e-mail: silvia.perezd@ehu.eus ...
The blackening of red cinnabar (α-HgS) pigment has traditionally been explained by its conversion into black metacinnabar (β-HgS). Scarce is however the scientific evidence that supports this hypothesis in polychrome artworks. As such transition occurs at around 345 °C, the thermal impact of the eruption of Mount Vesuvius in 79 AD could have induced this structural change of the pigment present in the mural paintings of Pompeii. This work aims to assess whether the mentioned volcanic eruption could be responsible of the cinnabar blackening through the formation of metacinnabar. The thermodiffractometry study of cinnabar-decorated fresco mock-ups stated that the formed β-HgS is not stable, observing its reversion into α-HgS. Moreover, sublimation of the cinnabar pictorial layer was registered, also when the cinnabar paint layer was protected by a coating of pyroclastic materials. In real blackened cinnabar Pompeian samples, it was not possible to identify metacinnabar by X-ray diffraction (XRD), but evidence of sublimation of mercury due to the thermal impact was observed. Hence, this blackening seems to be related mainly to the presence of calomel (Hg 2 Cl 2 ) and a gypsum (CaSO 4 ·2H 2 O) crust as degradation products of red cinnabar and the calcite mortar, respectively, and not to the formation of metacinnabar. Finally, laser-based techniques could also induce modifications in the HgS crystalline structure, resulting in an amorphous black product. Therefore, the elemental and molecular study of the species promoted by laser impact was carried out to avoid false positives in the metacinnabar detection or when the decorated surface has been subjected to laser cleaning.
Graphical Abstract
... The process is accentuated in presence of halide impurities ions (chlorine) and the formation of metallic Hg was observed. At high concentration the appearance of chlorine-based compounds was not excluded as found in other works [13][14][15][16][17]. ...
The application of no destructive techniques in the field of Cultural Heritage is becoming fundamental to understanding degradation phenomena. In this study, Transient Absorption (TA) spectroscopy was exploited to explain the process which causes the darkening of Red Vermilion, a famous pigment known also as cinnabar. The optical properties involved in the process are studied in pure HgS and chlorine doped HgS samples, before and after exposure to UV light (365 nm). The study was carried out with particular attention on the ground state bleaching signals, directly connected to the formation of intra-gap trap levels responsible for the pigment degradation. First derivative reflectance spectra reveal the presence of these defectivities, while the analysis of Tauc plots from Kubelka Munk function confirms the reduction of energy band gap due to UV exposure. With the help of Density Functional calculations, we simulated the role of S vacancies in producing a defective alpha-phase, the consequent reduction of the energy band gap and, finally, the progressive phase transformation to the cubic metacinnabar. Transient Absorption turns out to be an important tool of diagnosis about the conservation state of pigments applied in the field of Cultural Heritage
... The presence of cinnabar in wall paintings with a link to burials should be studied further before any conclusions can be drawn. The material properties and long-term instability might have turned cinnabar paintings black when exposed to light (McCormack 2000;Nöller 2015). But maybe cinnabar's toxicological effects were known or experienced by the Neolithic inhabitants too (e.g., Liu et al. 2006;Huang et al. 2012), hence its limited use or its use for special occasions. ...
... The presence of cinnabar in wall paintings with a link to burials should be studied further before any conclusions can be drawn. The material properties and long-term instability might have turned cinnabar paintings black when exposed to light (McCormack 2000;Nöller 2015). But maybe cinnabar's toxicological effects were known or experienced by the Neolithic inhabitants too (e.g., Liu et al. 2006;Huang et al. 2012), hence its limited use or its use for special occasions. ...
... 16,19,63 The Δ 199 Hg/Δ 201 Hg slope, together with very similar values of E 199 Hg (Surface emission) and Hg(0) emission fluxes at day-and nighttime, implies that the MIF observed during Hg(0) net emission from the cinnabar tailing was dominated by abiotic dark reduction and/or Hg(0) evaporation processes. Given that blackening of cinnabar ore is accompanied by formation of colloidal Hg(0) 64 and microscopic beads of elemental mercury frequently occur in cinnabar ores, 65 it is highly probable that evaporation of liquid elemental Hg is a major contributor to positive MIF during Hg(0) net emission from cinnabar. ...
... Different pathways for the blackening reaction have been proposed, including the formation of black metacinnabar (β-HgS) 8,9 . Many researchers consider the formation of a thin layer of metallic mercury to be responsible for the darkening 1,2,6,10 , based on the fact that colloidal mercury is black 11 . However, direct evidence for its formation on altered cinnabar paint has not been provided so far 1,2,6,10 . ...
Photo-induced darkening of red cinnabar (HgS) has attracted the interest of many researchers as it drastically impacts the visual perception of artworks. Darkening has commonly been related to metallic mercury (Hg ⁰ ) formation in the presence of chlorides. Based on the study of UV-aged cinnabar pigment and tempera paint we propose an alternative pathway for the blackening reaction of cinnabar, considering its semiconductor properties and pigment-binder interactions. We demonstrate that darkening is caused by the oxidation of cinnabar to mercury sulfates and subsequent reduction to Hg ⁰ via photo-induced electron transfer without the involvement of chlorides, and provide direct evidence for the presence of Hg ⁰ on UV-aged tempera paint. Photooxidation also affects the organic binder, causing a competing depletion of photo-generated holes and consequently limiting but not impeding mercury sulfate formation and subsequent reduction to Hg ⁰ . In addition, organics provide active sites for Hg ⁰ sorption, which is ultimately responsible for the darkening of cinnabar-based paint.
... The presence of Hg suggested the occurrence of vermillion and the moderate association of Hg and Cl (the correlation coefficient between Hg and Cl is about +0.50) may be linked to the darkened vermilion due to the well-known vermilion alteration in presence of halides [30]. It is interesting to highlight the relatively high association of As and Hg, which might point to a certain source of vermillion or its adulteration with an As-bearing pigment (e.g., realgar). ...
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The results derived from this research paper contributes to the body of knowledge available from Bagan painting materials and techniques and also to a treatment proposal for the conservation and restoration of Bagan’s temples.
Abstract
Pagán is an ancient city located in Myanmar that is renowned for the remains of about 4000 pagodas, stupas, temples and monasteries dating from the 11th to 13th centuries. Due to a magnitude 6.8 earthquake in 2016, more than 300 ancient buildings were seriously damaged. As a part of the post-earthquake emergency program, a diagnostic pilot project was carried out on Me-taw-ya temple wall paintings to acquire further information on the materials and on their state of conservation. This article presents our attempts at characterising the painting materials at Me-taw-ya temple using non-invasive portable energy dispersive X-ray fluorescence (ED-XRF), portable Raman spectroscopy and micro-invasive attenuated total reflectance—Fourier transform infrared spectroscopy (ATR-FTIR), micro-Raman spectroscopy (µ-Raman), gas chromatography-mass spectrometry (GC-MS), polarized light microscopy (PLM) and environmental scanning electron microscope—X-ray energy dispersive system (ESEM-EDS) investigations with the aim of identifying the composition of organic binders and pigments. The presence of a proteinaceous glue mixed with the lime-based plaster was ascertained and identified by GC-MS. In addition, this technique confirmed the occurrence of plant-derived gums as binders pointing to the a secco technique. Fe-based compounds, vermillion, carbon black and As-compounds were identified to have been incorporated in the palette of the murals.
... Firstly, McCormack (2000) highlighted that chlorine contents are decisive for cinnabar blackening. His research focused on natural deposits containing photosensitive cinnabar (generally associated with calomel, corderoite, terlinguaite and kleinite, eglestonite, comancheite, mosesite, radtkeite and kenshuite). ...
This article summarises the history of cinnabar, from its first uses in burials to modern oils on canvas. After a brief introduction on mercury and contamination issues, the article gets to the heart of the topic. First, mercury-based minerals significant for studying pigments, i.e. cinnabar, metacinnabar, hypercinnabar and calomel, are presented. Structural information and properties precede an overview of the geographic distribution of cinnabar deposits. The following section addresses the multiple uses of cinnabar, divided into funerary use, decorative use, lustre and Chinese lacquer production. The use of cinnabar for writing (ink), medicine and cosmetics is briefly described, and a shortlist of uncommon finds is further provided. The following section approaches inherent but less known topics such as cinnabar procurement, trade, production technology, application and alteration. An entire section is dedicated to calomel before concluding with an overview of the analytical methods for the characterisation and provenance investigation of cinnabar.
... Some scholars made the hypothesis of the transformation of cinnabar to metacinnabar (black form) but without any analytical confirmation [78,79]. Further studies are related to panel paintings [80][81][82] and Roman wall paintings [83]. Various mechanisms of red a-HgS degradation have been proposed, but the issue is still under discussion. ...
This paper presents the study of selected painted fragments from different contexts of Ostia Antica city, dating between 2nd century BC and the end of the 1st century AD. The aim is to identify the raw materials used and to understand the execution techniques through a non-invasive protocol including techniques based either on multiband imaging (Visible-VIS, Ultraviolet induced Luminescence - UVL and Visible Induced Luminescence - VIL) and single spot analyses (Fiber Optic Reflectance Spectroscopy- FORS and portable X-Ray Fluorescence spectrometry - XRF). The most representative and interesting fragments were sampled for further studies with laboratory techniques such as optical microscopy (OM) and electron microscopy (SEM), Fourier Transform Infrared and micro-Raman Spectroscopies (FT-IR and μRaman).
The extensive use of non-invasive techniques, even working on fragments, is proved to be the most robust and effective approach enabling the anaysis of a high number of areas, dramatically increasing the statistical meaning of the collected data. The elaboration of such a huge number of data allows highlighting differences and similarities, thus achieving a more realistic overview of the materials composition and addressing the sampling to the more significant and complex areas.
... Vermilion produced by the wet process is more vulnerable to degradation than the dry-processed pigment or the natural cinnabar (Eibner, 1914;Feller, 1967). The presence of small traces of chloride (Daniels, 1987;McCormack, 2000). White mercury chlorides, Hg 2 Cl 2 (calomel) and HgCl 2 , have been identified by several researchers in the greyish deteriorated surface layer on paintings using advanced analytical techniques (Spring and Grout, 2002;Keune and Boon, 2005;Cotte et al., 2006;Anaf et al., 2013). ...
... Microscopic analysis with the Transmission Electron Microscope (TEM, FEI Inc.) and Energy Dispersive X-Ray Spectroscopy (EDX, EDAX Inc.) indicates that Hg compounds in the agricultural soil may partly include Nano HgS, microscopic balls of liquid or colloidal Hg(0), and Hg-Al-Au-Ni amalgams or HgO adsorbed on clay minerals ( Figure S1 in the supporting information). A previous study suggested that the microscopic balls of liquid and colloidal Hg(0) and gaseous Hg(0) in sediments impacted by mine waste drainages represent a small fraction of the total Hg (<0.1%) (Bloom et al., 2003;Dreyfr, 1939;Gray et al., 2000;Jew et al., 2011). The native gaseous Hg(0) is soil samples might be lost during soil processing, but the bulk of the microscopic balls of liquid and colloidal Hg(0), which were coated with gas-impervious layer (Bloom et al., 2003), should be preserved. ...
Soil Hg(0) emissions are an important source of atmospheric mercury (Hg), but the Hg isotopic signatures of this source remain poorly characterized. In this study, the fractionation of Hg isotopes during Hg (0) emissions from Hg‐enriched agricultural and forest soils in Wanshan Hg mining area were investigated through laboratory experiments. Significant mass‐dependent fractionation (MDF) of Hg isotopes and mass independent fractionation of odd Hg isotopes (odd‐MIF) were observed. Mean MDF enrichment factors (ε²⁰²HgHg(0)‐soil) of agricultural soil were in the range of −2.03‰ to −1.34‰ for agricultural soil in light‐, light moisture‐, and temperature‐controlled experiments, which were higher than those of forest soil in similar controls (means = −3.38‰ to −1.98‰). Temperature‐controlled experiments exhibited a larger MDF compared to light‐ and light moisture‐controlled experiments. Photoreduction of Hg in agricultural soil in the presence and absence of soil water generated a larger positive odd‐MIF (mean E¹⁹⁹HgHg(0)‐soil = 0.67‰ to 0.76‰, n = 2) than the temperature‐controlled experiments (mean E¹⁹⁹HgHg(0)‐soil = 0.18 ± 0.04‰, 1 SD), whereas the E¹⁹⁹HgHg(0)‐soil of forest soil in temperature controls (mean = 0.23 ± 0.03‰, 1 SD) were higher than that in light (mean = 0.18 ± 0.06‰, 1 SD) and light moisture‐controlled experiments (mean = −0.03 ± 0.06‰, 1 SD). It is speculated that photoreducible Hg (II) likely dominantly bound to S‐containing ligands in agricultural soil but to both S‐containing and sulfurless ligands in forest soil, resulting in significant positive odd‐MIF in Hg(0) product during photoreduction in the former case and a small magnitude of positive to some negative odd‐MIF in the latter case.
... Kanvas üzerine yağlı boya ile uygulanan kırmızı renk ışık ve bağıl nem gibi çevresel koşullara ve inorganik kirleticilere maruz kaldığında, renk bileşenlerindeki bazı safsızlıklar (çözünmüş tuzlar ve boyamada kullanılan organik bileşenler) nedeniyle zaman geçtikçe oksidasyona uğrayarak yavaş yavaş geri dönüşü olmayan bir şekilde bozulur ve kırmızı renk koyu kırmızı, kahverengi veya grimsi beyaza dönüşebilir (Rytuba, 2003;McCormack, 2000; Abo-Taleb ve Orabi, 2019). ...
... The most common alteration of natural or synthetic cinnabar is due to the change in the typical red pigment colour to black or grey-silver hues. This phenomenon is not systematic and its origin is not yet fully understood (Vitruvius 1978b;McCormack 2000;Cotte et al. 2006;Cotte et al. 2010;Mazzocchin et al. 2010). Chlorine probably plays a key role in the process of photochemical alteration and could be present as an impurity in cinnabar or is derived from atmospheric pollution. ...
The Archaeological Museum of Palermo (Sicily) has recently presented the results of the restoration of three wall paintings from the House of the Masks of Solunto archaeological site. These significant paintings, dating back to the first century BCE, are the most significant examples of Pompeian style discovered in Sicily to date. The cycle of frescoes unearthed is the best preserved and most complete example of wall painting dating to the Republican Roman period in Sicily. This house was a luxurious private residence built on two floors and centred around a peristyle. This fresco cycle embellished the walls of a banquet room (oecus) discovered during an archaeological excavation carried out by Giovanni Patricolo in 1869. The House of the Masks definition was suggested by Salemi Pace in 1872 when he published the discovery of frescoes with colourful garlands and theatrical masks. In 1874, five panels were detached from the walls and moved to the National Museum of Palermo for conservation purposes. The recent careful cleaning of the pictorial surfaces and the new archaeological and archaeometric research revealed unusual details about the pictorial technique and newly painted subjects. The scientific investigation was preliminarily based on a non-destructive approach, performed in situ using portable equipment and subsequently, the further examination of a micro fragment using micro-destructive investigation. X-ray fluorescence analysis was carried out to identify the original pictorial palette, and electron microprobe analyses coupled with energy-dispersive X-ray spectroscopy to define the alteration products. Finally, infrared imaging provided new data about the pictorial technique and iconography. The new archaeometric evidence sheds light on these rare examples of Roman wall painting in the Sicilian Roman province, which until today have not been systematically studied from the point of view of materials and execution techniques, confirming the dating and connections with contemporary workshops active in other Roman provinces.
... As some authors have already pointed out, halides such as chlorine play ak ey role in this process. [15,[37][38][39][40] Bearing in mind that the considered samples are not pristine pyroclastic materials and have already been subjected to natural weathering (almost 2000 years) and leaching processes,t he quantitative values here presented do not reflect the maximum water-leachable contents of the nonexposed pyroclastic materials that still remain in the burial. Nevertheless,t he contribution of some ions (i.e., K + and SO 4 2À )c oming from specific pyroclastic strata is even higher than the concentrations found in the groundwater of the Phlegraean Fields.B esides,s ince the conductivity of the groundwater from the Somma-Vesuvius area is,atleast, eight times lower than the one of the Phlegraean Fields,t he ionic content of the groundwater below Pompeii is probably closer to the values extracted from the leachates of the pyroclasts, thus reinforcing the thesis of the pyroclastic materials as source of ions. ...
Pyroclastic strata have always been thought to protect the archaeological remains of the Vesuvian area (Italy), hence allowing their conservation throughout the centuries. In this work, we demonstrate that they constitute a potential threat for the conservation state of the mural paintings of Pompeii. The ions that could be leached from them and the ion‐rich groundwater coming from the volcanic soil/rocks may contribute to salt crystallisation. Thermodynamic modelling not only allowed to predict which salts can precipitate from such leaching events but also assisted the identification of additional sources of sulfates and alkali metals to explain the formation of the sulfates identified in efflorescences from the mural paintings of Pompeii. For the future, fluorine, mainly related to a volcanic origin, can be proposed as a marker to monitor the extent of the impact in the mural paintings of Pompeii in situ.
... Cinnabar tends to darken to be form of the black metacinnabar á-HgS [35]. The cause of cinnabar photosensitivity related to physical and chemical mechanisms such as photo-oxidation and changes in atomic structure [36]. SEM-EDS of dark red and blue sample shows white crystals spread on the surface, while the results analysis showed that it contains of chloride (Cl) and sodium (Na) and this indicates to the presence of halite (NaCl) as a salt which is a common salt in the sandy burial environment [37,38]. ...
The aim of this paper is to study deterioration phenomena of foot case cartonnage from Saqqara area, Egypt. There are many damage problems such as: accumulation of dust, stains, cracks of ground layer and detachment of paint and gilded layers. An analyses and investigations of different samples were performed using a number of different analytical techniques. Light microscopy (LM), X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive X-ray detector (EDS) and Fourier transform infrared spectroscopy coupled with attenuated total reflection (ATR-FTIR) were used. Analytical studies indicated that, cartonnage was composed of two layers; the coarse ground layer consisted of calcite and quartz as while the finer ground layer contained calcite only. Two layers of preparing double of linen textile were used as a separate layer between the previous ground layers. The pigments used for the decoration of cartonnage were identified as hematite, cinnabar and cuprorivaite. Gilded layer was identified as gold and silver. Microbiological investigation indicated the presence a fungal and bacterial infestation. The results obtained gave important knowledge about the deterioration processes of the foot case cartonnage.
... The cause of the red color change can be effectively explained in two separated stages. First, chlorine acts as a catalyst during the lightinduced conversion of mercury sulfide HgS (photo-oxidation) to Hg (0) and S (0) [7]. Then, mercury reacts with chlorine to form different mercury chlorine compounds. ...
... 1) Both inorganic and organic pigments change colour and nature, due to high light levels, fluctuating pH and contact with moisture and oxygen (Cronyn 1990, 118, Mora et al. 1984, Bearat et al. 1997, McCormack 2000. Practically this meant it was hard to determine if the variety of red tones used in the paintings were the original colours, or if they had changed due to the burial environment and exposure to air. ...
Neolithic site of Çatalhöyük (Turkey) presents the most detailed and the interesting story up to date on Neolithic art and technologies both for the prehistoric archaeology and the material science studies. Çatalhöyük wall paintings are significant in terms of understanding the ideas of beliefs, rituality, symbolism and the social organization within the Neolithic community as well as the development of Neolithic wall art, since there are no other Neolithic sites at which the wall paintings were found of a similar scale in sizes and varieties in representations. However the technological processes which these paintings were created by did not seem to be interconnected with the discussions on the social aspects. The constantly developing field of material science has proved that the social studies on these paintings would not be complete without the study of their technologies which ultimately created these images. For the first time, this research aims to investigate primarily the technological make up of these paintings in detail and tie up the previous studies on the Çatalhöyük pigments and plasters within a broader technological and social context. The nature of wall painting production as a whole i.e. the materials used and their interaction with each other, tools and techniques and how “specialized” this practice was within the Neolithic community were investigated with the variety of analytical techniques available in order to understand the painting methods and the use of materials/sources within their archaeological and technological context. The research showed that most households at Çatalhöyük have involved in the making of wall paintings, their selection of materials/techniques were developed via their close environment and the production work was based on long-lived practices and traditions which were created through simply discovering and experimenting. By undertaking this research, it was also possible to understand the nature of the individual wall painting materials and thus to develop better conservation strategies for their preservation whilst setting up parameters for their safe retrieval from soil, sampling, stabilizing and safe storage which will help to increase the level of information provided by these very old paintings.
... Calomel is uncommon in the mercury ores. It was found associated with cinnabar, eglestonite and liquid mercury at the McDermitt mine McCormack 1986), and with photosensitive cinnabar, terlinguaite and an Hg-S-Cl mineral, probably corderoite, at the Opalite mine (McCormack 2000). Recent discoveries of calomel crystals in silica-rich light gray rock associated with kleinite and terlinguacreekite presents an interesting association. ...
This is a minor change to the original article on the mineralogy of the McDermitt mine, Humboldt County, Nevada.
... Calomel is uncommon in the mercury ores. It was found associated with cinnabar, eglestonite and liquid mercury at the McDermitt mine McCormack 1986), and with photosensitive cinnabar, terlinguaite and an Hg-S-Cl mineral, probably corderoite, at the Opalite mine (McCormack 2000). Recent discoveries of calomel crystals in silica-rich light gray rock associated with kleinite and terlinguacreekite presents an interesting association. ...
This final report represents over four years of field and laboratory work on the mineralogy of the McDermitt mercury mine, Humboldt County, Nevada. Thirteen probably new mercury phases have been identified during this effort, adding new knowledge to the mineralogy of mercury deposits. Suggested paragenesis of the deposit is compared to that of the Clear Creek mercury mine, California. This deposit illustrated both a macro and micro environments for the formation of a host of mercury-bearing minerals. Because of the large amount of residual ore remaining, additional mercury phases are possible but it require a tremendous effort, both in the field and in the laboratory.
... Results are in agreement with the IR reflectography by which the transparency of cinnabar at 1000 nm highlights the lost pendants (both at left and right). The blackening of red can be explained as the well know degradation of cinnabar [19,20]. The P27 spectrum revealed the presence of zinc (Zn) and chromium (Cr) attributable to zinc white (ZnO) and chrome red (PbCrO4·PbO), respectively, added to surface during the pictorial retouches of this area. ...
The “Trionfo della morte” is a detached fresco painting dated at the half of the XV century. Its history is strictly connected with the history of Palermo and it is considered a symbol of the late Gothic period. Some small areas of the fresco were analyzed using a combination of non-invasive techniques and hand-held instrumentations (multispectral imaging analysis, X-ray fluorescence (XRF), and IR spectroscopy). The characterization of the nature of pigments used in its realization and restoration works was performed and some indications about its conservation state were obtained. More interestingly, some hidden details were revealed on the mysterious painting. They constitute additional evidence of the preciousness of the fresco.
... Cinnabar tends to darken to be form of the black metacinnabar á-HgS [35]. The cause of cinnabar photosensitivity related to physical and chemical mechanisms such as photo-oxidation and changes in atomic structure [36]. SEM-EDS of dark red and blue sample shows white crystals spread on the surface, while the results analysis showed that it contains of chloride (Cl) and sodium (Na) and this indicates to the presence of halite (NaCl) as a salt which is a common salt in the sandy burial environment [37,38]. ...
The aim of this paper is to study deterioration phenomena of foot case cartonnage from Saqqara area, Egypt. There are many damage problems such as: accumulation of dust, stains, cracks of ground layer and detachment of paint and gilded layers. An analyses and investigations of different samples were performed using a number of different analytical techniques. Light microscopy (LM), X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive X-ray detector (EDS) and Fourier transform infrared spectroscopy coupled with attenuated total reflection (ATR-FTIR) were used. Analytical studies indicated that, cartonnage was composed of two layers; the coarse ground layer consisted of calcite and quartz as while the finer ground layer contained calcite only. Two layers of preparing double of linen textile were used as a separate layer between the previous ground layers. The pigments used for the decoration of cartonnage were identified as hematite, cinnabar and cuprorivaite. Gilded layer was identified as gold and silver. Microbiological investigation indicated the presence a fungal and bacterial infestation. The results obtained gave important knowledge about the deterioration processes of the foot case cartonnage.
... That is to say pure cinnabar is not photosensitive, but it will become photosensitive after exposure to halogens. Pure HgS reacts with concentrated HCl at room temperature rapidly producing mixtures of photosensitive corderiote and cinnabar, which reveal vivid red initially but blacken rapidly on exposure to sunlight (McCormack 2000). The question about this transformation, however, is that the blackening of mercuric sulfurhalide should be upon exposure to light, while there was no evidence that jade artifacts turned black after excavation. ...
In mercury-contaminated soils, mercury sulfides (HgS) occur as nanoparticles in mineral surface coatings. The coatings are composed of ferrihydrite and its replacement by goethite results in the release of the HgS nanoparticles.
In this volume, Alexander Nagel investigates the use of polychromy in the art and architecture of ancient Iran. Focusing on Persepolis, he explores the topic within the context of the modern historiography of Achaemenid art and the scientific investigation of a range of works and monuments in Iran and in museums around the world. Nagel's study contextualizes scholarly efforts to retrieve aspects of ancient polychromies in Western Asia and interrogates current debates about the contemporary use of color in the architecture and sculpture in the ancient Mediterranean world, especially in North Africa and the eastern Mediterranean. Bringing a multi-disciplinary perspective to the topic, Nagel also highlights the important role of theory, methodology, and conservation studies in the process of reconstructing polychromy in ancient monuments. A celebration of the work of painters, artisans, craftsmen and -women of Iran's past, his volume suggests frameworks through which historical and contemporary research play a dynamic role in the reconstruction of ancient technological knowledge.
This chapter presents a summary of some of the results of Mazzucato’s doctoral dissertation; it assembles the work and suggestions of many of the members of the Çatalhöyük Research Project, and it is the outcome of the integration of a vast array of data collected by archaeologists and specialists during the 25 years of the Çatalhöyük Research Project. The current study explores the potential of network concepts and methods as a way to disentangle the dense set of relations that formed the social fabric of Neolithic Çatalhöyük at different chronological points during its development. It seeks to shed light on the dynamics of interconnectivity and cooperation between buildings, combining both an exploratory approach of observed networks and a hypothesis-testing methodology. For this study, networks are used as conceptual and methodological tools for integrating a range of archaeological data within a framework that privileges connections between entities instead of the entities in isolation.
The rhythms and organisation of daily life at Çatalhöyük were influenced by seasonal variation in the natural and social world its residents navigated. Seasonal changes in day length, temperature and rainfall shape overall productivity of the landscape (Fairbairn et al. 2005a). These biophysical cycles would have been punctuated by seasonal changes in the composition of local plant and animal communities, the seasonal presence of migratory species, and particular cycles of growth and maturation among resident populations (e.g., Russell, McGowan 2003; Pels 2010; Haddow, Knüsel 2017). The conceptions of seasonal patterns and activities shaped the ways in which Çatalhöyük’s residents interacted with their local environments, and structured the timing and spatial requirements of necessary tasks (Ingold 2000; Fairbairn et al. 2005a).....
It is widely known that the vivid hue of red cinnabar can darken or turn black. Many authors have studied this transformation, but only a few in the context of the archeological site of Pompeii. In this work, the co-occurrence of different degradation patterns associated with Pompeian cinnabar-containing fresco paintings (alone or in combination with red/yellow ocher pigments) exposed to different types of environments (pre- and post-79 AD atmosphere) is reported. Results obtained from the in situ and laboratory multianalytical methodology revealed the existence of diverse transformation products in the Pompeian cinnabar, consistent with the impact of the environment. The effect of hydrogen sulfide and sulfur dioxide emitted during the 79 AD eruption on the cinnabar transformation was also evaluated by comparing the experimental evidence found on paintings exposed and not exposed to the post-79 AD atmosphere. Our results highlight that not all the darkened areas on the Pompeian cinnabar paintings are related to the transformation of the pigment itself, as clear evidence of darkening associated with the presence of manganese and iron oxide formation (rock varnish) on fragments buried before the 79 AD eruption has also been found.
Pyroclastic materials buried and protected ancient Pompeii throughout the centuries. In this work, we demonstrate that they could represent a threat for the conservation state of the mural paintings, since rainwater and groundwater cause the leaching and transfer of ions to the mural paintings, promoting salt crystallisation. At Pompeii, the latter is one of the main causes of the detachment of the pictorial layers.
Abstract
Pyroclastic strata have always been thought to protect the archaeological remains of the Vesuvian area (Italy), hence allowing their conservation throughout the centuries. In this work, we demonstrate that they constitute a potential threat for the conservation state of the mural paintings of Pompeii. The ions that could be leached from them and the ion‐rich groundwater coming from the volcanic soil/rocks may contribute to salt crystallisation. Thermodynamic modelling not only allowed to predict which salts can precipitate from such leaching events but also assisted the identification of additional sources of sulfates and alkali metals to explain the formation of the sulfates identified in efflorescences from the mural paintings of Pompeii. For the future, fluorine, mainly related to a volcanic origin, can be proposed as a marker to monitor the extent of the impact in the mural paintings of Pompeii in situ.
Here, we demonstrate the use of pump-probe microscopy for high-resolution studies of vermilion degradation. Vermilion (mostly α-HgS), an important red pigment used in historical paintings, blackens over time, and metallic Hg and β-HgS have been implicated as possible degradation products. Conventional analysis techniques have trouble differentiating α- and β-HgS with sufficiently high spatial resolution. However, pump-probe microscopy can differentiate metallic mercury, α- and β-HgS, and map each distribution on the microscopic scale. We studied artificial degradation of α-HgS; femtosecond-pulsed laser irradiation induces an irreversible phase shift of α- to β-HgS, in which the initial presence of β-HgS grains can increase the rate of conversion in their vicinity. Continuous ultraviolet exposure instead generates both liquid Hg and β-HgS, with a conversion rate that increases with elevated temperatures. Last, we reveal the presence of β-HgS as a natural degradation product in discolored vermilion layers in a 14th century Italian painting.
Vitruvius’ De architectura is the only extant classical text on architecture, and its impact on Renaissance masters including Leonardo da Vinci is well-known. But what was the text’s purpose in its own time (ca. 20s BCE)? In this book, Marden Fitzpatrick Nichols reveals how Vitruvius pitched the Greek discipline of architecture to his Roman readers, most of whom were undoubtedly laymen. The inaccuracy of Vitruvius’ architectural rules, when compared with surviving ancient buildings, has knocked Vitruvius off his pedestal. Nichols argues that the author never intended to provide an accurate view of contemporary buildings. Instead, Vitruvius crafted his authorial persona and remarks on architecture to appeal to elites (and would-be elites) eager to secure their positions within an expanding empire. In this major new analysis of De architectura from archaeological and literary perspectives, Vitruvius emerges as a knowing critic of a social landscape in which the house made the man.
Cambridge Core - Ancient History - Author and Audience in Vitruvius' De architectura - by Marden Fitzpatrick Nichols
Corderoite, Hg//3S//2Cl//2, occurs in late Miocene playa sediments in association with montmorillonite, alpha -quartz, alpha cristobalite, and cinnabar. This paper describes the occurrence, genesis, and physical characteristics of corderoite. The case history was originally published in 1974.
Radtkeite, Hg3S2ClI, is a new mineral that occurs in small amounts with cinnabar and corderoite at one locality in the McDermitt mercury mine, Humboldt County, Nevada. The mineral occurs mostly as 2-μm grains and as finely dispersed grains, coatings, and prismatic crystals as long as 30 μm, some of which are hollow, in altered tuffaceous sediments. Radtkeite is orthorhombic, with possible space groups Fmmm, F222, or Fmm2; a = 16.85(1) Å, b = 20.27(2) Å, and c = 9.133(2) Å; V= 3119.4(5) Å3; and Z = 16. The four strongest lines in the X-ray powder diffraction pattern of synthetic material are (d Å, I/I0, hkl) 2.54, 100, 080; 2.65, 85, 313; 3.89, 48, 420; 2.71, 44, 620. Radtkeite is opaque in thick sections but translucent in thin grains. The mineral and streak are yellow-orange, and both blacken on exposure to sunlight. Luster is almost adamantine. Hardness is 2-3. Cleavages are: pinacoidal {010} perfect, {001} and {100} very good; prismatic {0kl}, {h0l}, and {hk0} good. Fracture is splintery, conchoidal, and hackly. Dmeas = 7.0 ± 0.1 g/cm3, and Dcalc = 7.05 ± 0.1 g/cm3. Preliminary optical measurements indicate that the mineral is biaxial (+), with 2Vz approximately 35°. Refractive indices are greater than 2.0. Pleochroism of thin plates is orange, orange with red tint, and orange with green tint. Reflected light properties of natural and synthetic radtkeite are: medium reflectance, slightly lower than cinnabar; color pale gray with yellow cast; strong anisotropism commonly masked by abundant canary yellow internal reflections. The polishing hardness is less than that of cinnabar; VHN = 65-75. Radtkeite formed during late stages of mineralization by reaction of cinnabar and corderoite with halide-rich hydrothermal solutions in a surface-dominated environment; it exists in several textures as a result of fluctuating saturation levels.
The first act of any photochemical and photophysical process is the absorption of a photon by a molecule (equation (1)). The excited state that
(1)
is formed in this way is a high energy, unstable species which must undergo some type of deactivation [1]. As shown in figure 1, excited state deactivation can occur via (i) disappearance of the original molecule and formation of products (photochemical reaction), (ii) emission of light (radiative deactivation, also called luminescence), (iii) degradation of excess energy into heat (nonradiative deactivation), and (iv) some type of interaction with other species present in the solution (quenching processes).
The blackening of powdered red mercury(II) sulphide suspended in aqueous potassium iodide, upon illumination, has been investigated. The blackened material is shown to contain metacinnabar, the black form of mercury(II) sulphide, by electron spectroscopy for chemical analysis, photo-acoustic spectroscopy, thermal analysis, and X-ray powder photography.