Formulating Clay Bodies for Rapid Open-Firings скачать в хорошем качестве

Formulating Clay Bodies for Rapid Open-Firings

Tim Willey - Independent Researcher and Educator (UK) It is a well-established proposition that the earliest ceramics were open fired - that is, fired without the aid of any heat-retaining structure. Archaeological evidence of pre-historic open-firing is rare, as the practice was by its very nature, transitory and left very little, lasting trace. However, open-firing traditions - which continue to the present day - provide clear evidence that these firings were often extremely rapid and carried out with little, or no, pre-heating of the vessels. To the experimental archaeologist, these techniques raise the fascinating but often problematic question of how air-dried pots can survive the characteristic and sometimes explosive temperature rise without spalling and dunting? Through several experimental firings and using a range of clay-body formulations, it is demonstrated that the established convention of adding tempering materials to a locally-sourced clay is only part of the solution. Far more important, is to consider the minerology, particle size and particle distribution of the body as a whole: an approach which considers the analysis of the clay and the temper as an integrated system, and one which can be designed to ameliorate the phase-change pressures of mechanically combined water. The results demonstrate that, historically, very workable bodies could be formulated that consistently survive rapid temperature rises to satisfactory ceramic temperatures. It has shown that firings can be achieved in well under thirty minutes and without the need for pre-heating. These outcomes have practical and theoretical implications for experimental firing generally, but more specifically, for firings that characteristically, have temperature/time gradients which are rapid, sporadic, or difficult to control. #EXARC #ExperimentalArchaeology #EAC12