David Woof on mon 6 mar 06
Dave, Yes, respond on-list. I wanted to see what you had behind your
previously posted statement regarding temperature being more important than
cones. By itself it seemed to infer information not stated. Thanks, good
information to share with everyone I think.
Best regards,
David
_________________________________
_________________________________
David Woof Studio
Clarkdale, Arizona
Ph. 928-821-3747 Fax. 866-881-3461
________________________________
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peering over the edge, reverently taking an irreverent look at everything.
>From: Dave Finkelnburg
>To: David Woof
>Subject: Re: refireing
>Date: Sun, 5 Mar 2006 13:38:12 -0800 (PST)
>
>David,
> Mind if I respond to this on-list? I will only do
>so on list with your permission. Thanks.
> Basically, cones deform due to high-temperature
>creep.
> Clay bodies vitrify through a number of mechanisms,
>starting with sintering and advancing to melting and
>crystallization. It is possible to put a cone down
>with a long, slow ramp or long soak at a given
>temperature, and to put the same cone down with a fast
>ramp, no soak firing schedule at a significantly
>higher temperature. It has been proposed that the
>degree of vitrification of the body in both cases is
>NOT identical, and possibly widely different, despite
>the fact that both firings were to the identical cone
>value.
> This is not much of an issue with a glassy glaze
>where one is just trying to get the glaze ingredients
>melted into a uniform glass. However, if
>crystallization is involved then it can make a
>difference.
> Heat work as a concept assumes an object absorbs
>heat and undergoes a single change, such as a cone
>bending. An analogy is ice melting to become water.
>There the degree of the change (amount of ice melted)
>is precisely proportional to the amount of heat
>transferred. Vitrification of a ceramic body,
>particularly a clay body which will ultimately be
>composed of a glass phase, mullite and undissolved
>material, after firing, is far more complex than the
>heat work concept recognizes.
> Still, cones and the idea of heat work are very
>useful. But when things go wrong it's useful to look
>more deeply into what's going on.
> Does this help any?
> Dave Finkelnburg
> Dave
>
>--- David Woof wrote:
>
> > Dave, seems that since a cone measures heat work of
> > both body and glaze,
> > shouldn't that be a more important indicator for
> > vitrification than temp.
> > alone? Can you elaborate to clarify this?
> > Thanks
> >
> >
> >
> > David
> > _________________________________
> > _________________________________
> > David Woof Studio
> > Clarkdale, Arizona
> > Ph. 928-821-3747 Fax. 866-881-3461
> > ________________________________
> > ________________________________
> > peering over the edge, reverently taking an
> > irreverent look at everything.
> >
> >
> >
>
>
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