[Clayart] kilns as ovens

Girrell, Bruce bigirrell at microlinetc.com
Mon Jan 9 10:33:57 EST 2017


L Turner wrote:
Oxygen *is* the fuel when you are in reduction.

No. Oxygen is always the oxidizer. The fuel is the still supplied by the burners. 

But in the case of reduction, the amount of oxygen provided along with the fuel by the burners is insufficient for complete combustion of the fuel, leaving a lot of very hot hydrocarbons (pieces of hydrocarbons) that are itching to combine with anything that they can find. Oxygen is available from oxides that we use in our glazes. Because of the high temperature, the carbon and the oxides are active enough that the carbon can "steal" oxygen from the glaze oxides. Electrons from the kiln atmosphere or from nearby atoms mate up with the orphaned metals in the oxides, reducing their valence number, which is why the process is called reduction.

I'm not trying to pick on you. I do feel however, that the chemistry of pottery processes is muddled and mysterious to many potters. Having contradictory information out there does not help the situation. Atoms do some odd and interesting things during inorganic reactions, but oxidation is always oxidation and reduction is always reduction regardless of which atom is losing (oxidation) or gaining (reduction) electrons.

Bruce "Mr. Pedantic" Girrell





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