True and Fake Red Layers on the Objects from Archaeological and Historical Context: Microscopic Observations
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2014, vol. 40 (2): 241–254 True and fake red layers on the objects from archaeological and historical context: microscopic observations Joanna Trąbska1, Barbara Trybalska2 1Rzeszów University, Institute of Archaeology; ul. Moniuszki 10, 35-015 Rzeszów; e-mail: [email protected] 2AGH University of Science and Technology, Department of Material Engineering and Ceramics; al. Mickiewicza 30, 30-059 Krakow, Poland; e-mail: [email protected] © 2014 Authors. This is an open access publication, which can be used, distributed and reproduced in any medium according to the Creative Commons CC-BY 4.0 License requiring that the original work has been properly cited. Received: 10 September 2013; accepted: 17 June 2014 Abstract: Colored layers on surfaces of objects associated with archaeological and historical context may be of various origins: natural or intentional and in numerous cases their exact identification is not obvious, especially for thousand-year-old objects. Yet, the diagnosing of their nature may constitute an important element for the interpretation of ancient cultures. Examples of red color layers of natural, intentional and unclear origin were chosen and observed to select criteria defining layers of uncertain parentage. Keywords: archaeology, red layers, paintings, weathering crusts INTRODUCTION Red was the first true color attractive to hu- mans (Petru 2006), and evidences of interest in it Colored layers on surfaces of objects associated reach deep into Paleolithic. In a distant time span, with archaeological and historical context may it is particularly difficult to distinguish between have been produced by humans deliberately or intentional and the natural colors or the imposi- “made” by nature; they may have arisen in a nat- tion of one to another. Diagnosing of their nature ural way, but have been generated by the specific may constitute an important element for the inter- cultural context. Colorful layer may appear be- pretation of the dawn of human culture. cause of restorers’ interventions: introduction of The problem of discrimination between in- a colored layer consciously or because of product tentional and natural red layer refers to not only time discoloration. In extreme cases, one must paintings but also fine-grained or cryptocrystal- reckon with counterfeiting. In any situation, it is line iron-bearing crusty concentrations of other important to identify a substance which formed origin. They may be remnants of rubbing red pow- the layer and to determine how it contacts with ders into various supports (Behrmann & Gonzales the ground, how thick and how homogeneous it 2009 – Fig. 5), even very specific, like a cemented, is; perhaps also to detect a specific painting tech- phosphatized ash from a hearth dated to 58,000 BP nique or traces of tools employed in a painting (Sibudu, South Africa, Wadley 2010). Red crusts process. It is crucial to define the natural and cul- appear on skeletal surfaces due to unknown ac- tural context from which the item originates. tions: rubbing a powder into a body, rubbing it into http://dx.doi.org/10.7494/geol.2014.40.2.241 ISSN 2299-8004 | e-ISSN 2353-0790 | Wydawnictwa AGH 242 Trąbska J., Trybalska B. a skeleton, applying a suspension, spraying a red Microstructure and chemical composition of dust or others. Cracks and crevices may have been a potential intentional layer may perfectly reflect infilled with red remnants after exploitation of a red the analogous features of a widespread red rocks raw material; it is a case of the Lovas site (Hungary from the surroundings. Some red paintings from & Dobosi 2006). Many sculptures and reliefs, now the Fumane Cave were executed with a pigment discolored, are believed to have been painted but of a composition identical with the pigment of the only microscopic traces may support these hypoth- cave’s terra rosa (Broglio et al. 2007). eses (Roussot 1994, Behrmann & Gonzales 2009). To numerous paintings, even as ancient as Archaeological artifacts may have become ca- Paleolithic, specific extenders used to be added sually contaminated by red powder dispersed in (Martin 1993: 261–264, Behrmann & Gonzales a sediment due to intentional actions (such con- 2009). They tend to be different from an under- centrations are known from numerous sites, e.g. ground and the recipes are repeatable, so that the Fumane cave, Broglio et al. 2007), due to their their presence points at human executed panting. immersion in red ash layers (present e.g. at the Analyses of organic bindings are not so promis- Dolni Věstonice I and Milovice sites, Moravia & ing, especially for very old crusts and paintings Oliva 2007) or natural red regolith of terra rosa (e.g. Paleolithic), excluding waxes, stable within type, abundant in numerous southern European very long periods of time (Riparo Dalmeri Cave, caves (e.g. Odile & Plassard 1995). Nevertheless, to Rosanò & Pelizzaro 2005). the authors’ knowledge, no hard evidence of such Iron compounds often precipitate on bone or contamination has been proved so far. shell surfaces producing brown-red and red col- Paintings and irregular patches that happen oration. It may appear difficult to discern results to occur together (e.g. the Aurignacian paintings of painting, rubbing, immersing or other human from the Fumane cave, Broglio et al. 2007) can be actions. Influence of natural processes is suggest- discerned when the two are compared on the basis ed by domination of brownish shade (especially in of microstratigraphy and petrographic analyses. a moderate climate), irregularity of patches con- In many dubious cases, an intentional action of tour, only partial covering of an object. The ob- painting may be identified due to specific appear- jects that have been interpreted as intentionally ance of a smoothened underground, infilling and colored are usually red or cherry on a whole sur- evening of microundulation (e.g. Trąbska 2001); face and a color shade is uniform (compare, for however, for many rock, cave, shell or stone paint- example, Aurignacian ivory pendants from the ings it does not occur (e.g. Broglio et al. 2007: 167). Betche-aux-Rotches cave, Lejeune 2007: 143). It Usually, thickness of paintings executed with should be remembered that some restoration pro- mineral pigments balances close to 0.2 mm (e.g. cesses may have altered original appearance. Roy 1993, Berry 2007). The pigments used to be Intentional layers that are most difficult to dis- very fine-grained and of homogeneous size, due to cern from natural crusts come from Paleolithic, careful grinding (the phenomenon observed also mainly due to time span and simpler or unknown for the rock paintings, e.g. Hoz de Vicente, Her- way of their execution compared to numerous nanz et al. 2010) but their particular appearance younger realizations. Microscopic cross-sections will always depend on an individual workshop of cave, rock, shell or stone paintings depict var- or painting technique. However, micromorpho- ious images: panting layers are cryptocrystalline logical features of a pigment itself may appear or fine-grained, usually the layers are clearly dis- indicative especially because ground iron-bear- cernible from an underneath but the contact may ing pigments tend to preserve their parental mi- be both sharp (especially for cryptocrystalline crostructure (Trąbska et al., manuscript). In this paint, e.g. Hoz de Vicente, Hernanz et al. 2010) way, the particles micromorphology may indicate or cloudy (for fine-grained paint; Fumane Cave, an external source of a raw material, different Broglio et al. 2007: 167; Abri Pataud, Chiotti et al. from in situ source. In some cases, hematite order- 2007). Painting layers may be inserted between ing may indicate at a pigment origin (Trąbska & layers of clay minerals, gypsum, oxalates and oth- Gaweł 2007, Hernanz et al. 2010). Unfortunately, er secondary phases (e.g. Hoz de Vicente rock art, detailed comparative analyses may be misleading. Hernanz et al. 2010). https://journals.agh.edu.pl/geol True and fake red layers on the objects from archaeological and historical context: microscopic observation 243 Last but not least, red colored surfaces were in- graphite. A low vacuum technique was applied. fluenced by deterioration: continuity of the layers Samples were observed in 3D dimensions, some- got lost (e.g. some paintings from the Yiwarlarlay times on surfaces of thin sections. in Australian North Territory, Watchman et al. 2000), images disappeared due to powdering (e.g. RESEARCH Behrmann and Gonzales point at the phenomenon for certain paintings from the Siega Verde cave, Historical context unspecified. 2009). Coloration was likely present on reliefs from Intentional red layers Cap Blanc (Roussot 1994) but its nature may be in- A case: Mural paintings (Vrbnik, Croatia). Red terpreted only based on the analyses of microtrace paint layer can be implemented using a wide range remnants. A change of phase composition of red of pigments, dyes and adhesives (Berrie 2007). iron pigments is less possible than for other pig- A sample comes from a depiction of a foundation ments but in some circumstances it is still possible. cross from ruined stone chapel. Painting layers In this paper, selected examples of red color were executed with an inorganic pigment. layers of natural, intentional and unclear origin Thickness of a painting layer is uneven but os- are presented. They were identified on the objects cillates around 0.2 mm. It penetrates into a very and surfaces: (a) from an archaeological context/ fine-grained carbonate underneath. The contact historical context, (b) from natural environment, is apparent but not very sharp, as if the painting (c) obtained in experimental research. Basic infor- was realized on a soft underlayer. Painting layer mation on tested material is listed in the Table 1. is composed of cryptocrystalline microclusters Observation and characteristics of the well-de- of iron compounds and fine grains of detritic fined color origin layers and layers of natural ori- quartz, feldspars and glauconite (Fig.