The Difference Between Oxidation and Reduction Firing

There are many ways to fire your clay. Artists experiment and develop new firing techniques and methods all the time. There are two primary methods most commonly referred to as Oxidation and Reduction firing. In addition there are offshoot methods like wood/pit firing and salt glaze firing. Included in the reduction firing there are additional techniques which will be discussed further in other articles, like Raku, Horse Hair, Bone/ash, etc.

Knowing how Oxidation and Reduction firing works, will help the ceramist to better understand the other types of firing as well as many techniques.

Oxidation Firing

Most commonly, the ceramist will use the Oxidation type of firing for their ware. This is typically done in an electric kiln; but can also be done in gas or propane kilns. In this process, the kiln has adequate oxygen to interact with the glazes during the firing stage. The results are most typically bright and rich colors.

Most of the commercial glazes on the market are designed to develop specific colors under the conditions of Oxidation firing. This firing can be accomplished at low or high temperature ranges. Oxidation results are predictable in that they will match the color intended by the manufacturer when fired to the temperature suggested by the manufacturer.

For final results in the color to be achieved, it is necessary for the presence of adequate oxygen during the last part of the firing process.

Reduction Firing

Most usually, reduction firing is favored by potters and is done using gas, propane or other fuel burning kilns or methods. Reduction firing is the exact opposite of Oxidation firing. It is the lack of oxygen in the last part of the process that is critical for the desired effects. Fuel burning kilns give the artist control of how much or how little oxygen enters the firing chamber and when. Preventing oxygen from interacting with the glaze maturation creates unusual and sometimes unpredictable results. There are many popular techniques that utilize reduction firing such as Raku, Horse Hair, Salt Glazing, and more.

The corrosiveness of these methods makes them undesirable for electric kilns.