The application of oxidizers and reductants seems to be common in the glass kiln, but in the ceramic kiln, oxidizers are naturally unnecessary because of the relationship between fuel and ventilation, and the application of reductants seems to be limited to very special cases. In other words, when local reduction in the same kiln or the same action on the same piece is expected, such as when coal lumps are enclosed in a saggars, or when a reducing agent is added to a part of the glaze. The addition of manganese to remove the bluish tint of glass is an example of an oxidizing agent, while the accidental addition of tin, which is thought to have been the cause of the local reddening in Chinese homogeneous kilns, is an example of a reducing agent.
