Why is it important to be oxidising, not reducing under 1000°C?
In an oxidising atmosphere there is sufficient oxygen to combust the carbonaceous matter (paper and plant material) within in the clay, or as used in fabrication. However, in the second glost firing, having previously bisque fired up to 1000°C in an oxidising atmosphere, this stage has been done once already. So for the first stage of a glost firing the main reason is that a reduction flame is very heat inefficient, a waste of fuel, and polluting. Reduction is required only when the glaze is beginning to melt, e.g over 800°C.
