Iron based earthenware in a forced reduction atmosphere

Abstract

Iron is a strong flux in ceramic glazes when fired in an oxygen-starved atmosphere (reduction), resulting in a CO rich atmosphere. The carbon monoxide (CO) robs the iron (Fe2o3) of two oxygen molecules, thus transforming the iron into FeO. It is when iron is in the FeO state that it becomes an active flux and it is this state of flux that I am interested in. Earthenware clay is an iron rich clay that is typically fired in an oxygen rich atmosphere where the iron in the clay maintains it’s maximum amount of oxygen. This results in a porous and non-vitreous clay, which typically requires the application of glaze or a vitreous surface to allow for safe utilitarian usage. I intend to research and develop a low-fire earthenware clay body that becomes vitreous due to the forced reduction atmosphere in which it will be fired. The intention is to develop a low-temperature food safe clay body that doesn’t require glaze for utilitarian applications. This will result in aesthetic alternatives to surface treatment and finishes. In this research I will formulate two different clay bodies, each varying in the amount of iron. Both of the clays will be fired in both oxidized and reduction atmospheres, allowing for comparable data from which saturation of carbon and vitrification can be tested. One set will be fired to 1954 ºF in an oxidation atmosphere, which will be used as the control. The reduction firings will also reach 1954 ºF in oxidation and then cooled in a reduction atmosphere down to 1500 ºF. It is in the cooling cycle that I anticipate the vitrification to occur.