David Beumee on wed 1 nov 06
Bruce wrote:
" One clay body that we use develops a beautiful toasty
> brown color during the cooldown. How do I know it occurs then? Draw rings
> that I pull at peak temperature and during the initial cooldown show nothing
> but a dull gray body color. As the cooldown progresses body color develops.
> It is very definitely a surface effect."
I love the clues I get from other potters experience through Clayart. How often in my testing of stoneware bodies have I seen the beautiful toasty color disappear as percentages of spar are added to the body as flux and to eliminate cristobalite. I will definately pursue extension of the cooling cycle to try to get the toasty color, even if it is a surface effect. Thanks!
David Beumee
-------------- Original message ----------------------
From: Bruce Girrell
> David Beumee wrote:
>
> > I'm sorry I can't tell you exact degrees fall per hour, ...
> > I fire at night, and I'm always too tired to watch that side of the curve.
>
>
> The Fluke Model 54 pyrometers (and others, too, I'm sure) can record your
> temperatures at regular intervals. I set mine to record temperature from two
> thermocouples every five minutes. This allows recording of a full cone 10
> firing, including preheat and the entire cooldown period.
>
> Reoxidation effects during cooldown play a very important role in the
> development of color. One clay body that we use develops a beautiful toasty
> brown color during the cooldown. How do I know it occurs then? Draw rings
> that I pull at peak temperature and during the initial cooldown show nothing
> but a dull gray body color. As the cooldown progresses body color develops.
> It is very definitely a surface effect. Just like with the bright shino
> colors, all you have to do is scratch through the surface and the underlying
> bland color shows through.
>
> Bruce Girrell
>
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