Jeff Lawrence on sat 11 aug 12
As I hoped, big pot #3 went from last coil applied to glaze fired in about
48 hours - I did a single fire because I didn't want to manhandle a 70 lb
pot (but I'm definitely impressed by Maggie's report of glaze-wrest;ling
her life-size human figures).
I started by pugging pyrophyllite and grog into the clay to open it up,
along with feldspar per RR's advice. Then, I tried to emulate the
industrial drying scheme by using my kiln chamber as humid hotbox
(something Richard confirmed the validity of trying). To hold humidity, I
closed flue/peeps and splashed water on the floor before turning pilot
ring on to its absolute minimum, which gave me a temp of 150F overnight.
Next day, I brushed on glaze and fired to 2230F, observing RR's caveats
about silica inversion temp of 1062F. I spent about an hour lollygagging
around this temp and saw no problems post-firing.
Unlike my experience with the "slower is better" approach some folks
advocated here, I found this approach better. There were none of the cracks
I expected in joints, bottoms pressed against bats and other regions
between fast-drying and slower-drying parts. Also,, I didn't have to devote
limited studio space to a slow-drying piece.
I suspect anyone working on a massive scale would also get better results -
the ceramic engineers whose method I was imitating contend that the
internal stresses it avoids get exponentially more troublesome with greater
mass.
Best,
Jeff
Craig Edwards on sat 11 aug 12
Hey Jeff: Do you have a picture of the pot.... or a thousand words would
also do:O)
--
Make Good Pots
~Craig
New London MN
http://woodfiredpottery.blogspot.com/
On Sat, Aug 11, 2012 at 1:28 AM, Jeff Lawrence wrote:
> As I hoped, big pot #3 went from last coil applied to glaze fired in abou=
t
> 48 hours - I did a single fire because I didn't want to manhandle a 70 lb
> pot (but I'm definitely impressed by Maggie's report of glaze-wrest;ling
> her life-size human figures).
>
> I started by pugging pyrophyllite and grog into the clay to open it up,
> along with feldspar per RR's advice. Then, I tried to emulate the
> industrial drying scheme by using my kiln chamber as humid hotbox
> (something Richard confirmed the validity of trying). To hold humidity, I
> closed flue/peeps and splashed water on the floor before turning pilot
> ring on to its absolute minimum, which gave me a temp of 150F overnight.
> Next day, I brushed on glaze and fired to 2230F, observing RR's caveats
> about silica inversion temp of 1062F. I spent about an hour lollygagging
> around this temp and saw no problems post-firing.
>
> Unlike my experience with the "slower is better" approach some folks
> advocated here, I found this approach better. There were none of the crac=
ks
> I expected in joints, bottoms pressed against bats and other regions
> between fast-drying and slower-drying parts. Also,, I didn't have to devo=
te
> limited studio space to a slow-drying piece.
>
> I suspect anyone working on a massive scale would also get better results=
-
> the ceramic engineers whose method I was imitating contend that the
> internal stresses it avoids get exponentially more troublesome with great=
er
> mass.
>
> Best,
> Jeff
>
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