CONICET | Buscador de Institutos y Recursos Humanos

SEM, EDS and XRD analytical techniques were applied to surface paintings of archaeological pottery from Aguada Ambato and Portezuelo styles (Catamarca, Argentina). Differences in mineral and chemical composition were found between them suggesting that they are two distinctive entities not only on their designs but also on the materials chosen and the technology used. Aguada Portezuelo paints are composed of Ca (white), Fe-Mn (black), Fe-Mn-Ca (dark reddish) and Fe-Ca (reddish). The whites correspond to gehlenite, a firing product (possible firing temperature ≥ 900-1000ºC); calcite and CaO occur in cases suggesting firing temperatures < 900ºC. Images and EDS spectra always depict the differences among paints. Aguada Ambato presents difficulties for paints discrimination by imaging; EDS spectra show light differences. White from Tricolor Ambato contains mainly Pb-phases (hatchite, anglesite, plumalsite), reddish resembles the paste with similar proportions of hematite; reddish surfaces may have not been painted but polished. Black on Tricolor has scarce Mn-minerals; on Black Incised sherds no particular phase was identified suggesting possible organic pigments or resulting from the firing technique. The chemical and mineralogical composition of the paste almost always overlaps that of the paints because the painted layer is irregular and partially worn by years of burial. BEI and XRI, were particularly worth for compositional differentiation, they obtain more superficial information than EDS spectra (from depths of 3-4µm). Image processing was necessary when the chemical contrast was not discriminated. Soft X-ray lines were more revealing than hard ones because the detected ones are coming from shallower depths, clearly reflecting the composition of the paint layer.