| Abstract: |
The aim of this paper is to reconstruct firing techniques of Yayoi pottery based on firing cloud patterns. A series of pot-firing experiments were conducted to correlate various types of firing clouds with firing methods. Previous studies have demonstrated that Jomon pottery was made with an 'open firing method,' in which pots were surrounded by firewood without any covering materials, whereas Yayoi pottery was made with a covered firing method,' in which pots were placed on firewood and covered with silica-rich grasses. The latter method is more fuel efficient, in that the silica-rich grasses burn into a layer of ash which produces a kiln-like structure. Based on an ethnographic analysis of pottery making in the rice-producing culture area, where the covered firing method is commonly used, pot-firing methods were examined for the effects of variation in the setting of fuel under the pots, the placement of the pots (the pot placement angle and the presence/absence of piling), and the kind of materials covering the grasses in the top layer. Early Yayoi pottery in the northern Kyushu district and Middle Mumon pottery in south Korea (slightly earlier than the Early Yayoi pottery) show distinct similarities in firing cloud patterns: a relatively low frequency of firing clouds on the interior surface, which indicates that hot flames penetrated well into the interior, and the presence of major firing clouds on the upper and/or lower exterior surface, indicating that pots were laid laterally on the fuel bed. These facts suggest that the covered firing method diffused from the Korean peninsula to northern Kyushu at the beginning of the Yayoi period, when wet rice farming was introduced. Changes in firing cloud patterns from the Early to the Middle and Late Yayoi periods suggest that pot firing techniques changed in accordance with changes in vessel shape, size, and thickness, in the following manner. First, Middle and Late Yayoi pots (wide-mouthed jars and necked jars) were placed at a higher angle (closer to upright) than Early Yayoi pottery. This is because as the pots became more constricted in the neck, they need to be placed at a higher angle so that flames could penetrate into the interior surface. Second, Early Yayoi and Korean Mumon pottery tends to have a more yellowish surface color than Middle and Late Yayoi pottery in the Honshu areas, suggesting that the former pots were fired in a strongly reducing atmosphere. Coupled with the fact that the method of firing with a mud covering (found in the contemporary Yunnan area) was present in the Early and Middle Yayoi period in the northern Kyushu district, it is hypothesized that Early Yayoi pots, which tend to be thicker than Middle and Late Yayoi pots, were fired with a more complete covering in order to improve the circulation of heat.
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