Estimating firing conditions for archaeological ceramics using gradual heating: the case study of Askasai 7 settlement ceramics (Sakhalin island)

The paper presents the results of estimating firing temperatures of Paleometal Age ceramic sherds discovered in the northern part of the Sakhalin Island by means of experimentation with gradual heating in a muffle furnace. The experimentation included analysis of the ceramic sherds retrieved by the archaeological excavations at the Askasai 7 settlement attributed to the Nabil archaeological culture (7th-4th centuries BC). The firing temperature was identified based on changes in the color and texture of the sherds. Presence of plant detritus detected by the petrographic study of thin sections is an evidence of low firing temperature. The experimentation results show that the changes in the texture and color spectrum occurred between 400 °С and 500 °C, which means that the firing temperature did not exceed this range. According to the obtained data of the petrographic study and the experimentation results, we think that the clay was fired in a bonfire without special structures. Low temperatures of bonfires suggest the use of raw material with low heat release or specific features of the firing season. At the same time thin-walled ceramic pots with tiny pores discovered in the dwellings at Askasai 7 are indicative of a well-established production process. Absence of grog in the temper is typical of expedient technology when, instead of pottery shops, ceramics were produced locally as needed. Presence of grog fragments in one sample and a different firing temperature employed suggest that this vessel was produced elsewhere and/or by a different potter.