DJBrewer88 on wed 15 dec 10
I've been taught to slow down my programmable electric kiln during
quartz inversion (950 to 1200 appx)
I usually slow it down to 100 degrees per hour during that phase of
firing. Do others do this? just wondering
DJ
Snail Scott on wed 15 dec 10
On Dec 15, 2010, at 1:38 AM, DJBrewer88 wrote:
> I've been taught to slow down my programmable electric kiln during
> quartz inversion... Do others do this?
Some clay bodies are more sensitive to quartz
inversion problems than others. If you don't have
problems, then don't bother. If you do, then you
should definitely take precautions!
Remember that quartz inversion only affects
vitrified clay, so it's the cooling phase, not the
heating phase, that will require slowed-down
temperature change.
-Snail
John Britt on wed 15 dec 10
DJ,
I don't do this.=3D20
I see people list in their bisque cycle- slow down for quartz inversion =
=3D
(e.g. Jeri=3D20
Virden's cycle listed in Ceramics Monthly October 2010, page 38).=3D20
There is no reason to do this on the way up as the clay is not vitrified =
=3D
(rigid).=3D20
Now, if I were refiring, then I would slow it down between 900 F and 1200=
=3D
F=3D20
since the clay is vitrified (rigid) and a rapid 1 - 2% contraction of the=
=3D
quartz=3D20
could cause cracking.=3D20=3D20
But unless you have cracking problems, I wouldn't slow it down through qu=
=3D
artz=3D20
inversion on cooling either. You don't need to fix a problem that doesn't=
=3D
exist.=3D20
Now if I have major cracking problems then I would consider adjusting the=
=3D
=3D20
cycle, depending on when the cracking occurred.
I think this is a just fear response which is then applied across the boa=
=3D
rd due=3D20
to a lack of understanding of quartz inversion.=3D20
I think it is a waste of time and energy.
Just my opinion,
John Britt
www.johnbrittpottery.com
DJ Brewer on wed 15 dec 10
Thanks very much for the input -- John and also "Snail." As I was
programming the firing this afternoon, I found myself wondering what was
the exact deal with a slow down during quartz inversion. I've seen
various people's firing ramps and they seemed to chug on through the
quartz inversion temp. Its funny. Now that I am firing things myself,
its like I think in terms of heatwork. It's just a natural perspective
-- like how to make watercolors flow on the page with the right amount
of water -- I'm just painting with heat, so I pay a lot of attention to
it since I am in essence applying brush strokes to the clay and glaze
with heat. OK if this analogy does not make sense to anyone else, its
fine. That's just how I feel about it. I love painting with heat.
It's amazing.
DJ
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