Horváth László szerk.: Zalai Múzeum 17. (Közlemények Zala megye múzeumaiból, Zalaegerszeg, 2008)

KREITER ATTILA: A Celtic pottery kiln and ceramic technological study from Zalakomár-Alsó Csalit (S-W Hungary). Kelta edényégető kemence és kerámia technológiai megfigyelések Zalakomár-Alsó Csalit lelőhelyről

each other but were not connected. The rounded frame of the kiln was carefully constructed because it was regular in size and its surface was flat and smoothed. The axis of the kiln was south-west oriented with the stokehole being situated at the eastern end of the chamber. Thus the kiln was fired from the east. The bottom of the chamber had a solid red burnt clay floor which is basically the clayey subsoil and no plastered bottom was identified. The bottom of the chamber was not hard but had a slightly red burnt appearance and it was covered with grey-black ashy filling. It is surprising that the frame of the kiln was hard and very well fired and the bottom of the firing chamber was not. This probably indicates that the frame of the kiln was deliberately fired. This seems somewhat obvious since the kiln frame supports the raised floor and holds the whole upper structure of a kiln. Thus the success of the operation of a kiln greatly depends on the careful preparation of the frame. Moreover, it was observed in the cross section of the kiln frame that towards the top of the frame and middle rib it was more thoroughly fired in red, and towards the bottom of the firing chamber the thickness of red burning decreases (Fig. 4b). The frame of the kiln survived exceptionally well in a height of 40 cm above the clay floor of the firing chamber. The majority of the raised floor survived showing 6-11 cm in thickness and a large part of it could be excavated in situ. The floor did not have sherds built into it. Macroscopically the raw material of the raised floor differs from that of the kiln frame although no microscopic analysis was carried out. In order to examine the construction method of the kiln during the excavation the subsoil around it was removed. It was observed that during the construction of the kiln the producers cross cut several clayey layers, which show differences in terms of the amount of sand and calcareous inclusions. The kiln frame was fonned within a clayey layer that contained smaller calcareous inclusions than the clayey layers above it. The raised floor, however, seems to be built from clay with larger calcareous inclusions than the kiln frame. Thus it seems that the raised floor was made from a clayey layer that the maker/s of kiln cross cut during the kiln construction, although this assumption is based on a macroscopic analysis and no chemical analysis was carried out. The raised floor was not solid but it was made of several layers of clay which can be observed in cross-section. It seems that the clay of the floor was kneaded and then applied in many layers that show a laminate structure. In the raised floor ventholes were pierced, which were arranged within each chamber in three arched rows (Fig. 2). The rounded vents were quite regular in size showing 3.5-4 cm in diameter although a 6 cm large hole also appeared when two holes were pierced so close so that they cross-cut each other. Most of the vents were pierced in angles about 60-70° degrees in such a way that heat was directed towards the middle of the kiln. The raised floor was not overly burnt, this could be accounted for by its relative thickness or perhaps the kiln was not used for a very long period. An interesting feature of the raised floor was that it did not sit on the kiln frame nor on a pedestal, as in the kiln construction method often observed in La Tène kilns (BONIS 1981, 11; ILON 1996-1997, 85; SOMOGYI 2004, 20). The raised floor sat within the chambers and where it was attached to the frame in the inside of the chamber it was thicker (11 cm) than towards the middle of the chamber (6-8 cm). Because the raised floor was excavated in situ it could be observed that it was attached to the upper part of the kiln frame within the firing chamber and it was not built on the top of the firing chamber (Fig. 4 a). The raised floor had a flat side where it was attached to the frame. The increased thickness of the floor where it was attached to the inside of the frame was probably due to increasing the cohesion between the firing chamber and raised floor. A further intriguing feature of the raised floor was that in the bottom of it imprints of 3-5 mm thick twigs were observed. The twigs were arranged in one row more or less parallel to each other but some twigs were also applied as a second row approximately in 45° degrees to the first row. Because twigs must have disintegrated at the first firing it is assumed that the twigs supported the raised floor during its construction. The twigs that composed the frame of the raised floor surely disintegrated at the first firing and the cohesion between the floor and the kiln frame probably could not have been strong enough to hold it in its position in particular because during firing every clay shrinks. Thus after the first firing the raised floor should have collapsed into the firing chamber, however this was not the case. Shrinkage depends on the type of clay but experiments show that it ranges between 6.5 and 14% (RICE 1987, 89, Tab. 4.3). Potters surely have been aware of clay shrinkage that they must put into consideration. In inspecting the characteristics of the excavated kiln it has been realised that the builders of the kiln chose a particularly interesting solution to overcome the clay shrinkage. They formed the frame and in particular the middle rib into a conical form. The rounded frame for example at its northern side measured ca. 10-14 cm on its top and tapered down towards its bottom showing ca. 17 cm. At the southern side the frame was ca. 13 cm wide on the top and 19 cm at its bottom. As it has already been mentioned the rib in the middle of the kiln was 17 cm thick on its top and tapered towards its bottom