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

the firing chamber of kiln 199 was 10-14 cm in thickness and circular went holes were arranged more or less in concentric circles (JEREM 1984a, 59). The pedestal, of course, is an excellent support for the raised floor of a very large kiln and it is sometimes found in this context (Békásmegyer, 3 m, NAGY 1942: 163), but pedestals were also used in quite small kilns (Sopron Krautacker kiln 151: 100 x 110 cm, kiln 199: 104 x 108 cm, JEREM 1984a, 59-60). The flues of the La Tène pottery kilns also show variability. At Gór-Kápolnahalom the width of the flue is 50 cm and its length is 37-40 cm but the flue was not divided into two parts (ILON 1996-1997, 85). The kiln at Garabonc Ofalu had two flues each measuring 42 cm in width. The dividing wall between them was 40 cm thick (HORVÁTH 1987, 63). A kiln (No. 199) at Sopron-Krautacker had one flue measuring 30 cm in length and 26 cm in height (JEREM 1984a, 59). A late La Tène kiln at Békásmegyer had two flues but the length of the flue is not specified (NAGY 1942, 163). The kilns usually have stoke holes but their size and shape show high variability. For example at Garabonc-Ofalu (LT-C2) the stokehole was rectangularshaped with rounded edges and measured 210 x 170 cm (HORVÁTH 1987, 63). At Ózd (LT-C) the size of the rectangular shaped stoke hole was 250 x 185 cm and the interesting feature of it is that its depth was 152 cm from the opening of the kiln and it could be loaded with fuel in a standing position (KOREK 1958, 80). The orientation of the kilns is also variable. For example at Sopron-Krautacker kiln 199 was west-east oriented being fired from the west (JEREM 1984a, 59), kiln 151 was oriented north-south and it was fired from the north (IBID., 60), kiln 332 was oriented northwest-south-east and it was fired from the north-west (IBID., 62). At Gór-Kápolnahalom the kiln was westeast oriented and it was fired from the west (ILON 1996-1997, 85). At Garabonc-Ófalu the kiln was fired from the east (HORVÁTH 1987, 63). It has been noted that Celtic kilns are faced towards the main wind direction and, since the dominant wind direction in the Carpathian Basin is west, north-west in this way potters used wind to achieve the appropriate oxygen flow and firing temperature (JEREM 1984, 95; ILON 1996-1997, 85). In this respect it seems that the pottery kiln at Zalakomár was faced opposite the wind direction. Does this practice indicate that these potters were un-knowledgeable? Potters exploiting wind direction is an interesting argument, however, there is evidence to suggest that this may not have been a good practice. Facing kilns towards wind direction may have made it difficult for the potter to effectively manipulate how much air gets into the kiln and this practice may have resulted in the breakage of vessels. Ethnographic examples indicate that during firing the temperature can suddenly increase by even 300 °C and often results in an increased waste (LEACH 1977, 195; REINA-HILL 1978, 24; GOSSELAIN 1992, 254, Figure 6). Wind can easily fan the fire resulting in uneven firing or overflring (warping, vitrified spots, and/or colour changes). Leach (1977, 180, 184, 195) notes that the evolution of kilns must have been governed by the necessity to conserve heat and exclude draughts because the kiln has to be protected from the wind. In the light of this the kiln at Zalakomár may have been purposefully directed opposite to the main wind direction. Variations in wind direction cannot be predicted and differences in facing the kilns represent a specific logic in which particular behaviour meet particular needs, however, the nature of these relationships needs further analysis. The firing chamber of Celtic kilns is often covered with a dome-shaped structure (KOREK 1958, 79; JEREM 1984a, 59, 1984b, 88; HORVÁTH 1987, 63; ILON 1996-1997, 85). Jerem (1984b, 88) notes that the kiln dome at Sopron-Krautacker was probably a temporary structure, which more or less had to be rebuilt at each firing. As it has already been mentioned the kiln from Zalakomár did not show any permanent structure on the top of the firing chamber. The dome of a kiln has important roles during firing such as retain heat and protect vessels from sudden changes in the firing atmosphere. Even though remains of a dome structure of Celtic kilns are often found, it has been pointed out that for non-vitrified wares the kiln does not necessarily need to have a permanent enclosure for retaining heat (KINGERY 1997, 13). This is important to note since Celtic ceramic samples examined by X-ray diffraction analysis from Sopron-Krautacker were nonvitrified wares, and were typically fired between 600-700 °C (JEREM 1984a, 67). For non-vitrified wares the crystalline clay structure breaks up to form an amorphous phase which agglomerates and sinters by surface diffusion (KINGERY 1997, 12). This process is rapid and does not require a long firing time. There is no doubt that some kilns were equipped with a clay dome, however, it would be very laborious to rebuild it after each firing, and experimental work has shown that a temporary cover of turf is an adequate way of conserving heat and fuel (PEACOCK 1982, 73) and it is easy to imagine a permanent cylindrical kiln structure with a temporary covering (dome). Experiments also show that for non-vitrified wares open firing system work just as well when the source of heat is rapidly burning organic material or any other combustible material distributed within, below and surrounding the wares (KINGERY 1997, 12), although