Nancy Udell on mon 22 jan 07
Hi all,
I am firing a lot of large patters, bottles and flat slab work. I
read in the archives some time ago that going slowly thru quartz
inversion (1067) on the way up and down will protect against
cracking. I have been adding into my firing schedule (for bisque and
glaze) two segments that go from 1000 to 1125 at 50 degrees per hour
on the way up and from 1125 to 1000 at 50 degrees per hour on the way
down. This adds about 6 hours to the firing schedule.
I'm thinking of cutting that back, but want to be conservative. I'm
wondering what schedules others use. This schedule (which I think I
got from the archives) is about 67 degrees on each side of 1067.
Could I do 45 degrees on either side? What about 75 or 80 degrees
per hour ramp rather than 50 degrees?
Any thoughts appreciated.
Nancy Udell
Santa Fe, NM
Ron Roy on thu 25 jan 07
Hi Nancy,
You don't have to go slow on the way up in a bisque - or in a glaze for
that matter. If you think about it - if the rim suddenly gets bigger during
the quartz inversion - on the way up - nothing will happen at our firing
speeds.
The problem is when the rim gets suddenly smaller because of the quartz
inversion - that causes cracking.
So keep the slowdown on the way down - that will work just fine. Keeping
those platters in the top half of the kiln will help as well because the
top half cools slower than the bottom half.
RR
>I am firing a lot of large patters, bottles and flat slab work. I
>read in the archives some time ago that going slowly thru quartz
>inversion (1067) on the way up and down will protect against
>cracking. I have been adding into my firing schedule (for bisque and
>glaze) two segments that go from 1000 to 1125 at 50 degrees per hour
>on the way up and from 1125 to 1000 at 50 degrees per hour on the way
>down. This adds about 6 hours to the firing schedule.
>
>I'm thinking of cutting that back, but want to be conservative. I'm
>wondering what schedules others use. This schedule (which I think I
>got from the archives) is about 67 degrees on each side of 1067.
>Could I do 45 degrees on either side? What about 75 or 80 degrees
>per hour ramp rather than 50 degrees?
>
>Any thoughts appreciated.
>
>Nancy Udell
>Santa Fe, NM
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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