Oxidation firing is firing a kiln with plenty of oxygen in the atmosphere, as electric kilns naturally do. Glazes and clays fire to clean, consistent colours, because oxides of iron, copper and other metals stay in their oxidised form.
What Is Oxidation Firing?
The atmosphere inside a kiln changes how colouring metals behave. In oxidation, iron tends to give ambers, browns and yellows, copper gives greens and turquoise, and cobalt gives blue. The results are predictable, which is a big reason electric kilns are the standard in community studios.
Gas and wood kilns can fire in oxidation too, when the burners get enough air. The opposite is reduction firing, where oxygen is starved and the same metals give different colours, such as copper reds and celadon greens.
Many modern glazes are formulated specifically for oxidation at cone 6, and some imitate reduction effects using other materials. Electric kilns still need ventilation, because the clay and glaze give off fumes as organic matter and carbonates burn off during the firing.
When you read a glaze recipe or a commercial label, check whether it was developed for oxidation or reduction, because the same glaze can look completely different in the other atmosphere.
This pottery glossary entry from Le Studio Art Space is general educational content. Always follow the clay, glaze and kiln makers’ data for your own materials and equipment.