The effects of kiln atmosphere on glaze color and texture

Abstract

This experiment studies the effects of the chemical colorants, red iron oxide (Fe2O3), copper carbonate (CuCO3), cobalt carbonate (CoCO3), black nickel oxide (Ni2O3), titanium dioxide (TiO2), and rutile, an iron contaminated titanium mineral, in five different glaze bases. As a control group, each glaze base will be fired without added chemical colorants. These glazes are then fired to pyrometric equivalent cone 10 (2340˚F). Pyrometric cones, which measure heat (a function of temperature over time), are standard use in studio ceramics. Each glaze will be fired in three different kiln atmospheres: reduction, oxidation, and reduction with the addition of sodium carbonate, or soda ash (Na2CO3). A natural gas fueled kiln will be in each case, with alterations made to fuel:air ratios to create reduction or oxidation atmospheres. A natural gas kiln will also be used in the firing implementing the soda ash, which will be introduced into the kiln at 2300˚F. The expected results include a variation of color and surface in the different kiln atmospheres. The reduction with soda ash atmosphere is expected to show the greatest variation in texture due to the addition of this vaporized chemical, which will unevenly coat the ceramic tiles in places and melt the glaze, adding areas of glossy surface and color variation. While the oxidation environment will show differences in color variation in comparison to the reduction atmosphere, especially within the glazes containing the addition of copper carbonate CuCO3. Test results from each group will be displayed for visual and tactile inspection.