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Areas Of Oxidation In An Otherwise Reduced Kiln


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Hello,

 

I have been firing a small gas kiln at the school I teach at and I am finding that about 1/4 of the pots are coming out oxidized, though most of the kiln load is reduced just fine, even with nice reds. Some pots even seem like the clay on the bottom is half reduction color and half oxidation color, which seems odd, and I think that it is causing brittleness in the ware. I am not exactly sure about placement, because another instructor usually unloads the kiln before I can observe it, but I think there is a bubble of full oxidation in this kiln, maybe in the lower left corner. Any ideas?

 

Thanks,

James

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Greg is amazing.

James, what kind of kiln are you using? Is it a little round updraft? There are specific shelf positions to improve the firings. One it to have a shelf at the top near the lid...maybe an inch gap. There are specifics for the bottom as well. Download the manual.

Marcia

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More info would be helpful- what size and type of kiln, type of burners, etc. In general, you can avoid pockets of oxidation by doing a thorough body reduction around cone 012-08 where you actually stall out the kiln for about 45 minutes, and make sure there's enough pressure in the kiln that you're getting flame out both the top and bottom spyholes. This primarily means closing down the damper enough to get the result, but also possibly adjusting the air and gas as well.

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