Shula on fri 12 jan 07
I have registered for the Steven Branfman raku workshop at Mother Earth Art Center in Sunnyvale, CA later this month. Most of the bisque pieces I have are made with Coleman porcelain. Does anyone have experience rakuing with it? When I lived on the East Coast, I used to raku with Standard porcelain or at least the cone 6 version of it and didn't have any problems.
Thanks
Shula
in unusually cold Redondo Beach, CA (forecast of 31 at 6am tomorrow)
Ron Roy on sat 13 jan 07
Hi Shula,
The problem with porcelain is it usually has about 25% free quartz in the
body - which goes through it's inversion at 573C - so putting a bisqued
porcelain pot into a hot kiln can result in cracking because of the uneven
heating (fast heating.)
If you could make such a body with amorphous silica - it- not being the
crystalline form of silica - quartz - you would have a much better chance
of avoiding the cracking.
To make maters worse - when you take the hot pot out the same uneven beta
to alpha quartz inversion takes place - again.
RR
>I have registered for the Steven Branfman raku workshop at Mother Earth
>Art Center in Sunnyvale, CA later this month. Most of the bisque pieces I
>have are made with Coleman porcelain. Does anyone have experience rakuing
>with it? When I lived on the East Coast, I used to raku with Standard
>porcelain or at least the cone 6 version of it and didn't have any
>problems.
>
>Thanks
>
>Shula
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Heather Pedersen on sun 14 jan 07
Hi Shula,
I have the bad habit of rakuing with cone 5 B-mix w/o grogg, and it almost
always develops hairline cracks where it is picked up to remove it from the
kiln, unless great care is taken.
For instance, anything I picked up only by one wall, or that fell over in
the can got cracked, but the 15 inch Navaho Wheel platter I fired on it's
edge, and very carefully picked up with two sets of tongs to carry it to
the can, did beautifully, with no problems.
Best of luck, and I look forward to seeing everyone's great work from the
workshop!!
-= Heather Pedersen
-= Member and Volunteer, Mother Earth Clay Art Studio.
On Fri, 12 Jan 2007 21:23:19 -0800, Shula wrote:
>Does anyone have experience rakuing with it? When I lived on the East
Coast, I used to raku with Standard porcelain or at least the cone 6
version of it and didn't have any problems.
>
>Thanks
>
>Shula
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