Shades of black: Production technology of the black slip ware from Barikot, north-western Pakistan

The archaeometric analysis of a set of potsherds of black slip ware found at the site of Barikot (Swat Valley, north-western Pakistan), dated between the Indo-Greek and the Kushan phases (middle 2nd century BCE-middle 2nd century CE), was addressed to define the provenance of this pottery and to constrain the production technology of both the ceramic body and the black external slip in terms of raw materials used and firing conditions. A multidisciplinary approach, consisting in the petrographic, mineralogical, chemical and spectroscopic (Mössbauer) analyses, was used to define possible differences between sherds archaeologically classified as grey ware, northern black polished ware and black gloss ware. The composition of this ceramic class resulted quite homogeneous, indicating the use of similar clay materials (low-calcium and both potassium- and iron-rich) and preparation procedures, with one exception represented by the only black gloss ware analysed. When samples are considered in diachronic terms, a progressive change can be observed, mainly related to a progressive intensification of the clay levigation. The petrographic nature of medium and fine sand-sized inclusions indicates that the pottery was produced within the region and possibly in Barikot. As for its production technology, the mineralogical associations indicate that the firing temperature was in the thermal interval between 650 °C and 950 °C, while the presence of spinel-like minerals, maghemite and wustite suggests that the firing was in reducing conditions. Important differences were observed in terms of paste and slip preparation for the black gloss ware with respect to the grey ware and northern black polished ware, which were interpreted also under an archaeological viewpoint.