How analytical techniques are able to address archaeological questions: a case study of a painted ceramic

Abstract

Application of instrumental analytical techniques has become essential when approaching the study of archaeological materials, as they provide information which can help to answer certain questions that are still unknown. Thus, this article presents the results of an interdisciplinary research conducted on a painted ceramic, whose fine and unusual decoration, of red and yellow colors raised doubts about the technological features and raw materials. The ceramic appeared incomplete and fragmented in the Tartesic site Cerro Borreguero, in Zalamea de la Serena (Badajoz, Spain). It is a burial mound from the beginning of the 6th century BC, which was closed and sealed by its own inhabitants when it was abandoned. Non-destructive and micro-destructive analytical and examination techniques were employed: reflected-light optical microscopy, field emission scanning electron microscopy for microstructural characterization of ceramic paste and painted layer, energy dispersive spectroscopy to determine elemental composition of materials and polycrystalline X-ray diffraction to identify the main crystalline compounds. The obtained data reveal the use of non-calcareous clay, with moderate content of iron in the form of osides. This and an oxidizing atmosphere during firing would explain the reddish color of the paste. And, regarding the decoration, the study confirms the application of a post-firing polychromy (employing natural ochres of iron oxides and hydroxides), which is uncommon in archaeological contexts, due to its difficult conservation. In addition, analyses performed with laser induced breakdown spectroscopy on rocks found in the same site prove the presence of natural ochres in the zone. Therefore, the pigments utilized to decorate the ceramic could come from a nearby area where the piece was found.