Lou Roess on wed 21 jan 04
Along with finding something to do while the kiln is cooling, I also
contemplate what tempertature to open it at. Poor grammar, but you know
what I mean. I have let a glaze firing cool to 212 F, which is a slow oven
in cooking, still have to use gloves and have some pieces pinging. I know it
doesn't matter quite as much for bisque, but what guidelines do you all use
for when to pull peeps, crack the kiln and open it all the way to unload?
Lou in Colorado
Reg Wearley on thu 22 jan 04
My reference for opening the kiln is related to
your kitchen oven-what is the hottest temperature
at which you would open the oven? Probably not as
high as 500 degrees, but you could safely open it
at 450 and not hurt your ceramic cookware-same
goes for your kiln. -- Reg Wearley
in beautiful
Big Arm, Montana
--- Marcia Selsor wrote:
> I always throw in a piece of newspaper to see
> if it ignites. If it does,
> then it is over 451 degrees Fahrenheit.
> (remember the Ray Bradbury's
> book or movie?)If it doesn't burn, then I crack
> the door. Quartz
> inversion is over by 500 degrees F. in my
> understanding.
> Marcia Selsor
>
> Lou Roess wrote:
>
> > Along with finding something to do while the
> kiln is cooling, I also
> > contemplate what tempertature to open it at.
> Poor grammar, but you know
> > what I mean. I have let a glaze firing cool
> to 212 F, which is a slow oven
> > in cooking, still have to use gloves and have
> some pieces pinging. I know it
> > doesn't matter quite as much for bisque, but
> what guidelines do you all use
> > for when to pull peeps, crack the kiln and
> open it all the way to unload?
> > Lou in Colorado
> >
> >
>
______________________________________________________________________________
> > 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.
> >
> >
>
>
______________________________________________________________________________
> 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.
__________________________________
Do you Yahoo!?
Yahoo! SiteBuilder - Free web site building tool. Try it!
http://webhosting.yahoo.com/ps/sb/
Marcia Selsor on thu 22 jan 04
I always throw in a piece of newspaper to see if it ignites. If it does,
then it is over 451 degrees Fahrenheit. (remember the Ray Bradbury's
book or movie?)If it doesn't burn, then I crack the door. Quartz
inversion is over by 500 degrees F. in my understanding.
Marcia Selsor
Lou Roess wrote:
> Along with finding something to do while the kiln is cooling, I also
> contemplate what tempertature to open it at. Poor grammar, but you know
> what I mean. I have let a glaze firing cool to 212 F, which is a slow oven
> in cooking, still have to use gloves and have some pieces pinging. I know it
> doesn't matter quite as much for bisque, but what guidelines do you all use
> for when to pull peeps, crack the kiln and open it all the way to unload?
> Lou in Colorado
>
> ______________________________________________________________________________
> 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.
>
>
Arnold Howard on thu 22 jan 04
From: "Lou Roess"
what guidelines do you all use
> for when to pull peeps, crack the kiln and open it all the way to unload?
That question was discussed at length several years ago on Clayart. People
came up with fascinating answers.
I feel that you should leave the kiln closed until it reaches room
temperature. I'll add, though, that opening the kiln while it's still hot
won't hurt the kiln. (But it may damage the ware.)
Sincerely,
Arnold Howard
Paragon Industries, L.P.
arnoldhoward@att.net
Ellie Blair on thu 22 jan 04
It depends on what you are firing and to what temperature. I have found =
that the best and safest is to let the ware cool until you can pick it =
up without gloves.=20
Hope this helps
Ellie Blair
Blair Pottery
Lawrence, Kansas 66047
----- Original Message -----=20
From: Lou Roess=20
To: CLAYART@LSV.CERAMICS.ORG=20
Sent: Wednesday, January 21, 2004 2:16 PM
Subject: What temperature to open kiln
Along with finding something to do while the kiln is cooling, I also
contemplate what tempertature to open it at. Poor grammar, but you =
know
what I mean. I have let a glaze firing cool to 212 F, which is a slow =
oven
in cooking, still have to use gloves and have some pieces pinging. I =
know it
doesn't matter quite as much for bisque, but what guidelines do you =
all use
for when to pull peeps, crack the kiln and open it all the way to =
unload?
Lou in Colorado
=
_________________________________________________________________________=
_____
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.
Undetermined origin c/o LISTSERV administrator on fri 23 jan 04
Dear Arnold Howard,=20
In general I go along with what you say, best leave the kiln to go dead =
cold. Regarding the refractories, they can suffer from the same degree =
of thermal shock as can the glaze on a mature pot or bisque clay. This =
could happen if a kiln is opened while the fabric inside is hot enough =
to cause minor burns to unprotected skin which comes into contact with =
the lining. I saw a kiln which had been so treated in a university =
facility. The refractory insulators were badly spalled, with inch thick =
sections of brick breaking away and falling into the kiln and onto the =
ware.
I believe that although he Quartz inversion is over 500=BAC . Though a =
Ron Roy tells us it is a rare occurrence, should there be any =
Cristobalite present in the body its phase change is in the 200=BAC =
region.
Best regards,
Ivor Lewis. Redhill, South Australia
Undetermined origin c/o LISTSERV administrator on sat 24 jan 04
Dear Reg Wearley,
You say <oven-what is the hottest temperature at which you would open the oven? =
Probably not as high as 500 degrees, but you could safely open it at 450 =
and not hurt your ceramic cookware-same goes for your kiln>> which seems =
to be a reasonable statement.
But there are some things which have to be considered. Ask yourself, =
"Are both the contents and the container at this temperature when they =
are removed from the oven ?" or "How can we be sure there is no damage =
to the pottery in this situation ?"
If you ever get the chance to examine some old time pottery, bean pots, =
stew pots and casseroles take note of the degree of crazing revealed by =
residues that have carbonised in the surface of the glaze. Have a look =
inside some old teapots. I would be interested to know what you find.
Best regards,
Ivor Lewis. Redhill, South Australia
Arnold Howard on mon 26 jan 04
Ivor, you are correct. Opening the kiln while it is hot can cause a gradual
cracking of the insulating firebricks, especially at temperatures above 900
deg. F.
Sincerely,
Arnold Howard
Paragon Industries, L.P.
arnoldhoward@att.net
----- Original Message -----
From: "Undetermined origin c/o LISTSERV administrator"
Dear Arnold Howard,
In general I go along with what you say, best leave the kiln to go dead
cold. Regarding the refractories, they can suffer from the same degree of
thermal shock as can the glaze on a mature pot or bisque clay. This could
happen if a kiln is opened while the fabric inside is hot enough to cause
minor burns to unprotected skin which comes into contact with the lining. I
saw a kiln which had been so treated in a university facility. The
refractory insulators were badly spalled, with inch thick sections of brick
breaking away and falling into the kiln and onto the ware.
Ivor Lewis. Redhill, South Australia
Bruce Girrell on mon 26 jan 04
> Probably not as high as 500 degrees, but you could
> safely open it at 450 and not hurt your ceramic cookware-same
> goes for your kiln
Don't forget about the cristobalite inversion that occurs around 200 degrees
C. That would make the maximum safe opening temperature less than 400 F and,
as has been pointed out in another post, the temperature of the kiln
environment it most likely cooler than that of the ware itself. So make that
maximum opening temperature around 350 degrees F or 175 degrees C.
Bruce "sorry, you'll just have to wait" Girrell
Ron Roy on wed 28 jan 04
What I have said consistently is that I have hardly ever seen any
cristobalite in a cone 6 clay body - only one in fact in the many I have
measured in my dilatometer - and then only a very small amount.
I do believe there is cristobalite developed in kiln brick that is fired
many times to cone 6. If anyone would care to send me a sample from the
inside face of liner brick that has been fired 50 times to cone 6 I will be
happy to measure it - and a sample fired 100 time for comparison.
If what I believe is true then opening a kiln above 150C (300F) would
contribute to the premature failure of the liner brick.
On the other hand - if you can't open your kiln at 100C (200F) and have
your ware intact - then you have a clay/glaze fit problem and it should be
fixed.
RR
All I need is a piece 3" long and a half inch square or a half inch in diame=
ter
>>Dear Arnold Howard,
>>In general I go along with what you say, best leave the kiln to go
>>dead cold. Regarding the refractories, they can suffer from the same
>>degree of thermal shock as can the glaze on a mature pot or bisque
>>clay. This could happen if a kiln is opened while the fabric inside
>>is hot enough to cause minor burns to unprotected skin which comes
>>into contact with the lining. I saw a kiln which had been so treated
>>in a university facility. The refractory insulators were badly
>>spalled, with inch thick sections of brick breaking away and falling
>>into the kiln and onto the ware.
>>I believe that although he Quartz inversion is over 500=BAC . Though a
>>Ron Roy tells us it is a rare occurrence, should there be any
>>Cristobalite present in the body its phase change is in the 200=BAC
>>region.
>>Best regards,
>>
>>Ivor Lewis. Redhill, South Australia
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
=46ax: 613-475-3513=20
| |
|
