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refiring to decrease reduction

updated wed 21 apr 04

 

r horning on sun 18 apr 04


I salt fired a sink with a beautiful cone 10 green glaze. Usually this glaze breaks to a beautiful emerald. It was in a part of the kiln that gets the most reduction. The glaze turned partially red. Not in an appealing way. In high reduction the glaze turns to Grey and red. If I re-fire in the electric kiln, can I get rid of the red? Would I have to take it to cone 10 or can I fire it to a lower temp?
Thanks for any advice, Rebecca


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Bruce Girrell on mon 19 apr 04


Rebecca Horning wrote:

> If I re-fire in the electric kiln,
> can I get rid of the red? Would I have to take it to cone 10 or
> can I fire it to a lower temp?

I wouldn't expect much change. Robert Tichane, in his book on celadons,
demonstrates that once a glaze has sealed over changing the kiln atmosphere
has little to no effect on the resulting color. Another example comes from
personal experience. I fired a shino in strong reduction to create a carbon
trap effect. The carbon trap worked fine, but the result was not to my
liking. I refired to cone 10 in a much more oxidizing environment and the
carbon did not go away. If I can't get carbon to react with oxygen then I
wouldn't hold much hope for getting a metal to do so.

Of course, if you don't like the results, what do you have to lose by
refiring it?

Bruce "if at first you don't succeed, fire that sucker again" Girrell

dianamp@COMCAST.NET on tue 20 apr 04


I have refired glazes in an attempt to decrease reduction,
and it worked!

Some shinos that came out too dirty from a cone 6 reduction firing
were, after refiring in an electric kiln to the same temp,
warmer in color and some of the carbon disappeared.

Diana

Jocelyn McAuley on tue 20 apr 04


I disagree with Tichane. I have refired cone 9 electric fired work at
cone 06 and at 1500F, in reduction, with resulting chnges of color of
the work. But then again- I haven't refired to lessen reduction, only
to gain its effects.

This list has also previously discussed how refiring shinos and other
glazes in a bisque fire can significantly change the color. I believe
Clay Times or PMI carried an article on this.

Bruce is right- just do it! Such is the spirit of experimentation,
nothing ventured, nothing gained.

Jocelyn McAuley

Bruce Girrell wrote:
> Rebecca Horning wrote:
>
>
>>If I re-fire in the electric kiln,
>>can I get rid of the red? Would I have to take it to cone 10 or
>>can I fire it to a lower temp?
>
>
> I wouldn't expect much change. Robert Tichane, in his book on celadons,
> demonstrates that once a glaze has sealed over changing the kiln atmosphere
> has little to no effect on the resulting color. Another example comes from
> personal experience. I fired a shino in strong reduction to create a carbon
> trap effect. The carbon trap worked fine, but the result was not to my
> liking. I refired to cone 10 in a much more oxidizing environment and the
> carbon did not go away. If I can't get carbon to react with oxygen then I
> wouldn't hold much hope for getting a metal to do so.
>
> Of course, if you don't like the results, what do you have to lose by
> refiring it?
>
>