OUT OF THE PERIODIC CHART AND INTO THE FIRE

The ancient human occupation of pottery-making continues to be a practive of testing igneous and metamorphic processes, for the creation of functional (or not) art objects. Mixtures of kaolinite, quartz, feldspar, oxide minerals and carbonates are subjected to high temperatures in various types of kilns. The type of kiln and fuel used in the firing are determined by the maturation temperature requirements of the clay and desired glaze effects. The composition of the atmosphere in the kiln during firing controls rates of temperature climb and/or the color of glazes containing susceptible oxides (e.g. iron and copper). Oxygen-depleted atmospheres in kilns burning fossil fuel, wood or other organic material produce large amounts of the unstable carbon monoxide molecule, resulting in color changes over limited temperature ranges. Introduction of large amounts of rock salt into the kiln atmosphere during firing produces sodium silicate glass on the surfaces of unglazed pottery. This talk will focus on the geologic and chemical processes involved in the production of pottery, with an eye toward educational collaborations among geology, chemistry and art students. Ceramics departments, common at most universities, can be sites of scientific research into melt behavior, atmospheric controls in firing, chemistry of clays and glazes, which all come together in the kiln.