william schran on sun 29 jul 01
To those thinking about adding insulation over your kiln lid -
I tried this by simply laying some scrap Kaowool on top of our L&L
2927 (29' diam.). Seemed to help a bit bringing down firing time, but
not by much. What I did notice, towards the end of one firing I
carefully lifted up part of the fiber and was surprised to see the
IFB was glowing red, on the exterior face! A few firings later I
noticed a small crack forming in the lid brick. The cracking had
continued across the lid and spread out. I finally quit using the
extra insulation, flipped the lid over and shoved lid cement in the
cracks on the outside face (was the inside before) and tightened the
banding. No more cracking, but I only use this kiln for bisque now.
I don't know if the extra insulation resulted in the cracking due to
more expansion/contraction of IFB, but I'm not doing it anymore.
Bill
Fabienne Micheline Cassman on mon 30 jul 01
At 08:17 AM 07/29/2001 -0400, you wrote:
>I don't know if the extra insulation resulted in the cracking due to
>more expansion/contraction of IFB, but I'm not doing it anymore.
>Bill
That's interesting you should mention that. The first few firings I ever
made on my then bran new kiln, I used some fiber on top of the lid. I
didn't pick it up to see if it glowed, but a hair-like fissure developed on
the underside of the lid. After I noticed that the fiber would degrade and
before I knew it wasn't a good idea to have fiber loose like that, I
removed it. The fissure has not moved since.
It could have been because it was bran new and had never been
expanded/contracted. Maybe the metal as a buffer would help afterall... I
don't see cracks on the side of the kiln...
I wonder if any of our kiln experts out there could comment on this and if
anyone who uses extra insulation have had this.
Cheers,
Fabienne
--
Milky Way Ceramics http://www.milkywayceramics.com/
Yes, I have learned from my mistakes...
I can reproduce them exactly.
Arnold Howard on tue 31 jul 01
I don't think the crack in the firebrick lid was due to insulation
placed on top of the lid.
The reason the firebrick lid was red-hot on the top is that the
insulation held in the heat. I don't see how that would cause a
crack in the lid. Cracks are due to an extreme difference in
temperature from one area of the brick to another. If anything, I
would think the insulation should lessen the chance of cracking.
Paragon has made an insulated lid for our square H-17 and K-6 kilns
for several decades. The insulation has never been detrimental to
the firebrick in the lid.
Reasons the firebrick cracks:
a) Firing too fast.
b) Cooling too fast. (You can hear the bricks crack if you open the
lid and cool the interior at high temperature.)
c) Mechanical pressure (placing a weight on the lid or not allowing
the lid enough room for expansion during firing).
This is an interesting subject. I hope others have information to
share on it.
With best wishes,
Arnold Howard
Paragon
--- Fabienne Micheline Cassman
wrote:
> At 08:17 AM 07/29/2001 -0400, you wrote:
> >I don't know if the extra insulation resulted in the cracking
> due to
> >more expansion/contraction of IFB, but I'm not doing it anymore.
> >Bill
>
> That's interesting you should mention that. The first few
> firings I ever
> made on my then bran new kiln, I used some fiber on top of the
> lid. I
> didn't pick it up to see if it glowed, but a hair-like fissure
> developed on
> the underside of the lid. After I noticed that the fiber would
> degrade and
> before I knew it wasn't a good idea to have fiber loose like
> that, I
> removed it. The fissure has not moved since.
>
> It could have been because it was bran new and had never been
> expanded/contracted. Maybe the metal as a buffer would help
> afterall... I
> don't see cracks on the side of the kiln...
>
> I wonder if any of our kiln experts out there could comment on
> this and if
> anyone who uses extra insulation have had this.
>
> Cheers,
>
> Fabienne
>
__________________________________________________
Do You Yahoo!?
Make international calls for as low as $.04/minute with Yahoo! Messenger
http://phonecard.yahoo.com/
| |
|
