Earl Brunner on thu 9 mar 06
Tell them you will need to deliver on Monday. Your time here is too short.
Earl Brunner
Las Vegas, NV
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Bonnie
Sent: Thursday, March 09, 2006 6:57 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: refiring underfired pots in electric kiln
Hi - I'm doing a project for my daughters' school. I told them I'd have
the pots ready by tomorrow! I opened the kiln and they were just a tad
underfired (just below cone 10). I've readjusted the doohickey on the
kiln sitter so it shouldn;t drop so easily. It should refire to the proper
temperature. I'm wondering if there are any 'rules' out there. Can I
fire on A - or would that be too fast? What would you all suggest? Thank
you very much.
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Bonnie on thu 9 mar 06
Hi - I'm doing a project for my daughters' school. I told them I'd have
the pots ready by tomorrow! I opened the kiln and they were just a tad
underfired (just below cone 10). I've readjusted the doohickey on the
kiln sitter so it shouldn;t drop so easily. It should refire to the proper
temperature. I'm wondering if there are any 'rules' out there. Can I
fire on A - or would that be too fast? What would you all suggest? Thank
you very much.
William & Susan Schran User on fri 10 mar 06
On 3/9/06 9:57 PM, "Bonnie" wrote:
> I opened the kiln and they were just a tad
> underfired (just below cone 10). I've readjusted the doohickey on the
> kiln sitter so it shouldn;t drop so easily. It should refire to the prope=
r
> temperature. I'm wondering if there are any 'rules' out there. Can I
> fire on A - or would that be too fast?
I would suggest you fire using witness cones rather than relying on the
Kilnsitter.
You can refire, but raise the temperature slowly at the beginning as the
ware is dense and more susceptible to breaking from thermal shock if the
temperature goes up too fast. Once you get in the range of 900=B0F - 1000=B0F,
you can fire faster.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
Gary Harvey on sat 11 mar 06
come on guys they are already partially vitrified. It is alright to fire
them fast now they don't have any water in them to explode. My kiln is
controlled by a cone sitter too. I would put witness cones 9,10. near the
peep hole and set it on low low, (because I have two switches) wait one
hour, then medium medium, wait one hour then high high, them watch till its
done. Watch the witness cones closely due to the fact you adjusted the
sitter. When the 9 cone bends over and the 10 starts to bend you are ready
to shut it off. If the cone9 hasn't bent when the sitter shuts off , then
over ride the sitter till the witness cones bend right. Don't overfire! and
WATCH it closely if you over ride the sitter because it will NOT shut off on
its on. FIRE DANGER!!!!! Gary Harvey, Palestine TX
----- Original Message -----
From: "Bonnie"
To:
Sent: Thursday, March 09, 2006 8:57 PM
Subject: refiring underfired pots in electric kiln
> Hi - I'm doing a project for my daughters' school. I told them I'd have
> the pots ready by tomorrow! I opened the kiln and they were just a tad
> underfired (just below cone 10). I've readjusted the doohickey on the
> kiln sitter so it shouldn;t drop so easily. It should refire to the proper
> temperature. I'm wondering if there are any 'rules' out there. Can I
> fire on A - or would that be too fast? What would you all suggest? Thank
> you very much.
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
Earl Brunner on sat 11 mar 06
Thought you might like to see what a message looks like to the moderator
when it comes through.
Yeah, Gary you can fire them faster than a bisque where you have to be
concerned about the moisture, but we have had mixed results on refires in
electric kilns to cone 6 depending on a variety of factors.
Some claybodies thermal shock more than others.
Electrics seem to radiate heat from the outside wall of the kiln to the
center different than a gas kiln.
The breakage we have experienced has been on the way UP, not on the way down
(you can tell by looking at the melted glaze on the edge of the cracks.
Some shapes are more prone to this than others, such as wide flat things.
So a little caution, especially going through quartz inversion doesn't seem
out of line.
Earl Brunner
Las Vegas, NV
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Subject: Re: refiring underfired pots in electric kiln
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come on guys they are already partially vitrified. It is alright to fire
them fast now they don't have any water in them to explode. My kiln is
controlled by a cone sitter too. I would put witness cones 9,10. near the
peep hole and set it on low low, (because I have two switches) wait one
hour, then medium medium, wait one hour then high high, them watch till its
done. Watch the witness cones closely due to the fact you adjusted the
sitter. When the 9 cone bends over and the 10 starts to bend you are ready
to shut it off. If the cone9 hasn't bent when the sitter shuts off , then
over ride the sitter till the witness cones bend right. Don't overfire! and
WATCH it closely if you over ride the sitter because it will NOT shut off on
its on. FIRE DANGER!!!!! Gary Harvey, Palestine TX
----- Original Message -----
From: "Bonnie"
To:
Sent: Thursday, March 09, 2006 8:57 PM
Subject: refiring underfired pots in electric kiln
> Hi - I'm doing a project for my daughters' school. I told them I'd have
> the pots ready by tomorrow! I opened the kiln and they were just a tad
> underfired (just below cone 10). I've readjusted the doohickey on the
> kiln sitter so it shouldn;t drop so easily. It should refire to the proper
> temperature. I'm wondering if there are any 'rules' out there. Can I
> fire on A - or would that be too fast? What would you all suggest? Thank
> you very much.
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
Ivor and Olive Lewis on sun 12 mar 06
Dear Gary Harvey,=20
You say.."...come on guys they are already partially vitrified. It is =
alright to fire
them fast now they don't have any water in them to explode...".
True, but you are ignoring the fact that there might be free quartz or =
some form of free silica that has been fixed during the initial =
vitrification. This will undergo its usual phase changes, and hence =
volumetric changes, as temperature rises. So heating rate will need to =
be retarded during these transitions otherwise the ware may Dunt.
Just a minor point but an important one to consider.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
L. P. Skeen on sun 12 mar 06
Thank you Ivor! That is exactly right; you have to go slowly through =
quartz inversion at least, even if partially vitrified. Dunting is very =
ugly!
L
----- Original Message -----=20
From: Ivor and Olive Lewis=20
Dear Gary Harvey,=20
You say.."...come on guys they are already partially vitrified. It is =
alright to fire
them fast now they don't have any water in them to explode...".
True, but you are ignoring the fact that there might be free quartz or =
some form of free silica that has been fixed during the initial =
vitrification. This will undergo its usual phase changes, and hence =
volumetric changes, as temperature rises. So heating rate will need to =
be retarded during these transitions otherwise the ware may Dunt.
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