Firing Spots and the Covered Open Firing of Yayoi Pottery

Abstract

From a series of firing experiments and a comparative analysis of the ethnographic literature on pottery production, we identified the formation processes of firing sites and conducted an analysis of black firing spots on Yayoi pottery. As a result, we clarified the following points regarding the open firing method.
(1) During the covered open firing of Yayoi pottery, (i) firewood was placed all over the ground surface but arranged only around the pots; (ii) firewood was not placed inside pots; (iii) during the Middle and Late Yayoi, because firewood was not placed at the sides, top or on the ground surface, we can call this a fuel economy type. In the Initial and Early Yayoi, and in the Korean Plain Pottery that formed the roots of Yayoi ceramics, more fuel was used than in the Middle and Late phases.
(2 ) In order to improve the transfer of heat at the ground surface during covered open firing of the fuel economy type, pots which had a large surface area touching the ground when placed sideways, were supported and placed slightly vertically. Supports were not used for (i) pots that had spherical bodies where the heat could reach the underside even when placed sideways, (ii) pedestalled vessels, or (iii) pots where a lot of firewood was placed next to the sides, top and ground surface, i.e., pots of the Initial and Early Yayoi and the Hakoshimizu type. In these cases the pot was simply laid sideways or only slightly raised.
(3 ) Compared to the Middle and Late Yayoi, in the Initial and Early phases (i) pots had more firewood fuel placed at their sides, tops and ground surfaces, showing that the intention was to use a lot of fuel; (ii) because more firewood was placed on the ground surface, kame (cooking pots) were more frequently fired in a sideways position; and (iii) because kame had wide mouths, firewood was infrequently leant against the rim. These features of firing are shared with pots of the Middle Plain Pottery phase in Korea suggesting that Yayoi pottery increasingly evolved its own characteristics from the Middle Yayoi.
(4 ) In the Yayoi period, with the exception of the Tohoku region, firing switched from an open to a covered method because (i) changes in settlement location made firewood for fuel a precious commodity; (ii) the application of red color to pots changed from a method in which color was applied after firing to a black or brown surface to a red slip technique that required constant and equal firing; and (iii) with the JomonYayoi transition, the ratio of storage and serving vessels with less sand temper increased. These three factors relate to the characteristics of Yayoi covered open firing: (i) it was fuel economical; (ii) firing quality was improved by using straw as a covering; and (iii) the temperature and firing time could be easily controlled by varying the type and quantity of straw covering.