Characterization of the binders and pigments in the rock paintings of cueva la conga, nicaragua

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Book Chapter

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Cueva la Conga is the first limestone cave with paintings and modified speleothems found in Nicaragua. Dating of images made with inorganic pigments generally requires the presence of an organic binder. Chemical characterization of the organic material in the paint was undertaken using thermally assisted hydrolysis/methylation-gas chromatography-mass spectrometry (THM-GC-MS). Results show that significant quantities of organic material are present in the rock itself, precluding dating of the paints based on binders. Some of the inorganic paints, however, contain traces of charcoal, possibly from calcination of the iron oxide pigments to change their color. We have successfully dated charcoal from the paintings using plasma-chemical oxidation and accelerator mass spectrometry. This study considered the composition of the substrate when sampling of the rock art to be dated, and emphasizes the importance of rigorous sampling protocols in analysis of rock art.

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