[Clayart] downfiring book/bogle/SEND A BUCK

Paul Gerhold via Clayart clayart at lists.clayartworld.com
Thu Apr 23 07:27:18 EDT 2015

Of course down firing changes the results when crystal formation either micro or macro is needed  to make the glaze work. That is a given and matches my experience.  But my question is does it actually help with other types of glazes and if so does anyone have the science.  My guess is that it doesn't help much, if at all where crystal formation is not required.  

If the glaze you tested is a rutile blue it probably does rely on crystal formation so down firing would change the results.  Whether or not the change is an improvement would be in the eye of the beholder.


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On Apr 22, 2015, at 11:42 AM, "Girrell, Bruce" <bigirrell at microlinetc.com> wrote:

> Pauk Gerhold wrote:
>> I have yet to hear a good explanation of why down firing helps glazes that are not dependent on crystal formation.
> I don't have the explanation, but I would suggest that a large fraction of our glazes - essentially anything that is not totally transparent - are dependent on crystal formation during the cooling phase and thus would respond to down firing. The crystals involved are most often not macro crystals, but they are important just the same and often add a lot of the "life" to a glaze. I still have a set of draw rings that clearly show the development of rutile blue during the cool down. Wouldn't you think that the effect would change if I extended the cooling period by downfiring?
> Bruce Girrell

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