Rachael Rice on sun 31 mar 02
I have a 11 month old Skutt 1227 and when I removed my bottom shelf to
vacuum it out the other day I saw a wider than hairline crack going all
the way down the middle from one end to the other. It was directly
under where my two shelves meet in the middle. I changed the positions
of the bottom shelf but is this normal or should I not be seeing this in
a new kiln? Is there anything I should be doing about it ? Thanks
Rachael
Dave Gayman on sun 31 mar 02
In my experience, both the lid and the bottom crack. There's a lot of
movement in the heating and cooling that's part and parcel of firing.
It becomes bad when the cracks proliferate and the expansion and
contraction of heating and cooling begin to cause wear along the cracks. I
had one electric kiln I bought new whose bottom was beginning to dish after
6 years, firing probably 4 times a week, 3 bisque and 1 cone 8
oxidation. The top was worn but still okay. I had a second, very used
kiln for bisque that had a well-cracked up, pretty flobbery top & bottom,
but it didn't much matter -- no big pieces of firebrick fell out.
Make sure your outer shell bands are tight (there should be screw
adjustments, probably two for both top and bottom.) Don't tighten to the
point they rip out.
Why a split shelf at the bottom? If you have supports at the center of the
bottom (supporting the center of the two long straight sides of the two
split shelves) as well as around the sides (as you would have with a full
shelf), it's going to stress the bottom as weight bears down on the center.
Just to double-check -- people still generally put a bottom shelf in
electric kilns, up about 1/2" from the kiln bottom, right? Or was I
misinformed back in the late 60s about the necessity of doing this?
Dave
At 10:00 AM 3/31/2002 -0500, you wrote:
>I have a 11 month old Skutt 1227 and when I removed my bottom shelf to
>vacuum it out the other day I saw a wider than hairline crack going all
>the way down the middle from one end to the other. It was directly
>under where my two shelves meet in the middle. I changed the positions
>of the bottom shelf but is this normal or should I not be seeing this in
>a new kiln? Is there anything I should be doing about it ? Thanks
Arnold Howard on mon 1 apr 02
Your concern about the cracked kiln bottom is understandable.
However, unless the crack is severe, it is nothing to worry about.
The cracks close tightly during firing. A greater cause for alarm
would be a cracked lid, because it is a source of dust falling onto
glazed pieces.
Arnold Howard
Paragon Ind. Inc.
--- Rachael Rice wrote:
> I have a 11 month old Skutt 1227 and when I removed my bottom
> shelf to
> vacuum it out the other day I saw a wider than hairline crack
> going all
> the way down the middle from one end to the other. It was
> directly
> under where my two shelves meet in the middle. I changed the
> positions
> of the bottom shelf but is this normal or should I not be seeing
> this in
> a new kiln? Is there anything I should be doing about it ?
> Thanks
>
> Rachael
>
>
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Arnold Howard on mon 1 apr 02
Having an extra shelf on the bottom of the kiln is not always
necessary. The extra thermal mass of the shelf can cause the bottom
to fire cooler than the rest of the kiln.
Arnold Howard
Paragon
--- Dave Gayman wrote:
>
> Why a split shelf at the bottom? If you have supports at the
> center of the
> bottom (supporting the center of the two long straight sides of
> the two
> split shelves) as well as around the sides (as you would have
> with a full
> shelf), it's going to stress the bottom as weight bears down on
> the center.
>
> Just to double-check -- people still generally put a bottom shelf
> in
> electric kilns, up about 1/2" from the kiln bottom, right? Or
> was I
> misinformed back in the late 60s about the necessity of doing
> this?
>
> Dave
>
> At 10:00 AM 3/31/2002 -0500, you wrote:
> >I have a 11 month old Skutt 1227 and when I removed my bottom
> shelf to
> >vacuum it out the other day I saw a wider than hairline crack
> going all
> >the way down the middle from one end to the other. It was
> directly
> >under where my two shelves meet in the middle. I changed the
> positions
> >of the bottom shelf but is this normal or should I not be seeing
> this in
> >a new kiln? Is there anything I should be doing about it ?
> Thanks
>
__________________________________________________
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Les Haworth on mon 1 apr 02
Rachael, don't worry about the crack. All kilns get cracks in them. The only
time you need to worry is when you can see light thru the crack. Then you
can try to patch it. Otherwise Don't worry. Hope this helps. Les H.
Lester R. Haworth III
Sales and Technical Support
Laguna Clay Co.
14400 Lomitas ave
City of Industry, CA 91746
1(800) 4-LAGUNA ext. 229
(626)330-0631 ext. 229
les@lagunaclay.com
www.lagunaclay.com
"The title of Artist is self-proclaimed!" Les H.
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of Rachael Rice
Sent: Sunday, March 31, 2002 7:01 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: [CLAYART] Crack at bottom of Kiln
I have a 11 month old Skutt 1227 and when I removed my bottom shelf to
vacuum it out the other day I saw a wider than hairline crack going all
the way down the middle from one end to the other. It was directly
under where my two shelves meet in the middle. I changed the positions
of the bottom shelf but is this normal or should I not be seeing this in
a new kiln? Is there anything I should be doing about it ? Thanks
Rachael
____________________________________________________________________________
__
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.
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