State of the art μXRF (micro X-ray Fluorescence) instruments allow the acquisition of high quality elemental data not only from single points but from two-dimensional surfaces as well. This allows the recording of spatially resolved elemental composition data, which can be a great asset for technological and provenance studies of ancient pottery.

The μXRF instrument in this work offers resolution of 25 μm and is equipped with an automated sample stage allowing acquisition of elemental maps across flat sherd sections, at maximum 100x magnification. Mapping was conducted on polished sherd surfaces, sherds embedded in resin (left-over from thin-section preparation) and thin-sections themselves, to identify the optimum preparation procedure. The measurement itself is non-destructive so, regardless of preparation method, the sample remains available for further studies.

Elemental maps can be processed according to spectral characteristics to extract ‘phases’ (clay matrix, mineral or lithic clasts). Each phase should be quantified using an appropriate calibration protocol to minimise systematic errors on obtained compositions. Several reference materials were created specifically for the purposes of analysing ancient ceramics, thereby limiting reliance on industry standards, which may not closely match this type of samples. Reference material bulk compositions were determined according to certified protocols by an external laboratory, using ICP-OES and ICP-MS. These materials were analysed by μXRF in powdered form (pressed pellets) and as polished sections of fired briquettes, in order to create multiple quantification calibrations for the ceramic elemental maps. Reference materials were chosen amongst geological samples collected for the purposes of provenance studies on the island of Cyprus, in order to match the locally made pottery that was also analysed. These references may derive from Cypriot geological contexts but they cover a diverse range of raw materials for pottery production (marly clays with various carbonate/silicate ratios, igneous and alluvial clays), applicable in other cases as well.

Ultimately, the above approach provides: a) raw spectral and image data for semi-quantitative assessment and phase analysis, b) spatially resolved elemental data (comparable to petrographic fabric analysis) and c) 'bulk composition' data (from whole sherd maps).
Original languageEnglish
Title of host publication13th European Meeting on Ancient Ceramics
Publication statusPublished - 2015
Event13th European Meeting on Ancient Ceramics - Athens, Greece
Duration: 24 Sep 201526 Sep 2015

Conference

Conference13th European Meeting on Ancient Ceramics
CountryGreece
CityAthens
Period24/09/1526/09/15

ID: 18874504