Karin Givon on sun 16 nov 08
Oh Pat! I built a kiln oncet and couldn't afford arch bricks and
built the dam thing anyway and I could fire it easily to bisk and
then! The Christmas Fire! The roof fell in at cone 5. Huh. I didn't
have any pots but I remember it with laughter and I shake my head at
myself and grin. That was a long time ago. I'd know now, that I
could actually SAW some bricks if I had to, or something. But it held
up (for a while) . Turned out to be a good kiln after i fixed it
right. ;>}
Karin
Nevada City, CA
On Nov 16, 2008, at 2:36 PM, Pat Lindemann wrote:
Hi Vince,
Thank you for your answer! Yes, I know...here in the northland, we
do have
more issues due to the centrifugal force :) ...but by far, my biggest
beef
right now is the shorter days...I could never live in Alaska or
somewhere
where the sunlight is even more limited in the winter.
As far as the solutions to why my bricks are falling in- OK, that makes
sense...I like the 2nd solution best. I have a supply of hard
firebrick,
and IFBs- I just thought that if I built the shell from something, I
should
make the door bricks out of the same stuff...on the same wavelength,
I could
re-do my door bricks and put them "length in", so to speak, instead of
length across, making the door bricks 9" thick? That might be a summer
possibility, but I think I will just do a door of hard firebrick,- 2
layers-
for now...
Thank you for your help
the learning curve sucks sometimes, but nothing ventured, nothing
gained!
Pat
On Sun, Nov 16, 2008 at 12:05 PM, Vince Pitelka
wrote:
> Pat in SD wrote:
> "Last night- the firing was going well, cone 9 was on
> the way down on one side, cone 8 was softening on the other side- I
> wandered
> into the studio for a bit and when I came back outside to check the
> cones-
> they were gone on one side (my first clue something was wrong), and by
> pulling back the fastening on the door an inch, I could see that
> the top
> few
> bricks of the arch had fallen in. Looking in the peephole
> confirmed that
> pots were laying on their sides and tipped. Ugh!
>
> Pat -
> The problem is that in South Dakota, the horizontal circumference
> of the
> earth is less, and therefore the centrifugal force is far greater,
> and this
> is causing your door to fall in during firing. People were not
> meant to
> live that far north.
>
> Okay, now for a serious answer. With only 5" of thickness, I expect
> that
> your homemade castable is shrinking on the inside surface where it is
> getting hottest, causing the door to lean inwards during the firing.
> That's
> one of the disadvantages of homemade castable. What recipe did you
> use?
> With door blocks only 5" thick, I don't think that there is any way to
> avoid
> this. As I see it, you have three choices. First you could cast
> thicker
> door blocks from your homemade castable, so that they will be more
> stable
> during the firing. Second you could brick up the door with 9" of
> standard
> hardbrick, with frequent header courses tying together the two
> layers of
> hardbrick. Third, you could make a modular fiber door, but I would be
> worried about carcinogenic fibers floating around whenever you move
> the
> door.
>
> I hope this helps -
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
>
Pat Lindemann on sun 16 nov 08
I have searched the archives for any reference to this, and aside from a few
comments from Snail and Vince, haven't found much... Here is the situation,
I have an approx 38 cu.ft.downdraft catenary arch kiln, with one large
burner positioned back on one side of the chimney. The door is a brick-up
type, with bricks made of the same castable that the kiln body is made of,
cut and fit to the door-5" thick. Over the bricked-up door, I have a piece
of steel that is backed by 1" of fiber that I place over the brick-up
door(fiber side in) and fasten in place. This is the 2nd time I have fired
this kiln, and both times the bricks at the top of the door have fallen in
to the kiln during the firing. The first time was a bisque firing, and I
chalked it up to me not bricking them tightly enough, and that there may
have been a slight lean. But this last time, I was relentless about making
the bricks fit tightly, and "chinking" with fiber in all of the loose spots-
the door was tight! Last night- the firing was going well, cone 9 was on
the way down on one side, cone 8 was softening on the other side- I wandered
into the studio for a bit and when I came back outside to check the cones-
they were gone on one side (my first clue something was wrong), and by
pulling back the fastening on the door an inch, I could see that the top few
bricks of the arch had fallen in. Looking in the peephole confirmed that
pots were laying on their sides and tipped. Ugh! I am picturing pieces of
fiber stuck to pots stuck to pots.
Is there any chance this is due to pressure in the kiln...??? Or it trying
to suck air, and pulling in the bricks?
Mostly I need to know how to fix this problem...maybe I just build a fiber
module door, but the potters of old had bricked up doors...what am I doing
wrong!?
thank you for any wisdom you can share
Pat
in SD
Vince Pitelka on sun 16 nov 08
Pat in SD wrote:
"Last night- the firing was going well, cone 9 was on
the way down on one side, cone 8 was softening on the other side- I wandered
into the studio for a bit and when I came back outside to check the cones-
they were gone on one side (my first clue something was wrong), and by
pulling back the fastening on the door an inch, I could see that the top few
bricks of the arch had fallen in. Looking in the peephole confirmed that
pots were laying on their sides and tipped. Ugh!
Pat -
The problem is that in South Dakota, the horizontal circumference of the
earth is less, and therefore the centrifugal force is far greater, and this
is causing your door to fall in during firing. People were not meant to
live that far north.
Okay, now for a serious answer. With only 5" of thickness, I expect that
your homemade castable is shrinking on the inside surface where it is
getting hottest, causing the door to lean inwards during the firing. That's
one of the disadvantages of homemade castable. What recipe did you use?
With door blocks only 5" thick, I don't think that there is any way to avoid
this. As I see it, you have three choices. First you could cast thicker
door blocks from your homemade castable, so that they will be more stable
during the firing. Second you could brick up the door with 9" of standard
hardbrick, with frequent header courses tying together the two layers of
hardbrick. Third, you could make a modular fiber door, but I would be
worried about carcinogenic fibers floating around whenever you move the
door.
I hope this helps -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Pat Lindemann on sun 16 nov 08
Hi Vince,
Thank you for your answer! Yes, I know...here in the northland, we do have
more issues due to the centrifugal force :) ...but by far, my biggest beef
right now is the shorter days...I could never live in Alaska or somewhere
where the sunlight is even more limited in the winter.
As far as the solutions to why my bricks are falling in- OK, that makes
sense...I like the 2nd solution best. I have a supply of hard firebrick,
and IFBs- I just thought that if I built the shell from something, I should
make the door bricks out of the same stuff...on the same wavelength, I could
re-do my door bricks and put them "length in", so to speak, instead of
length across, making the door bricks 9" thick? That might be a summer
possibility, but I think I will just do a door of hard firebrick,- 2 layers-
for now...
Thank you for your help
the learning curve sucks sometimes, but nothing ventured, nothing gained!
Pat
On Sun, Nov 16, 2008 at 12:05 PM, Vince Pitelka wrote:
> Pat in SD wrote:
> "Last night- the firing was going well, cone 9 was on
> the way down on one side, cone 8 was softening on the other side- I
> wandered
> into the studio for a bit and when I came back outside to check the cones-
> they were gone on one side (my first clue something was wrong), and by
> pulling back the fastening on the door an inch, I could see that the top
> few
> bricks of the arch had fallen in. Looking in the peephole confirmed that
> pots were laying on their sides and tipped. Ugh!
>
> Pat -
> The problem is that in South Dakota, the horizontal circumference of the
> earth is less, and therefore the centrifugal force is far greater, and this
> is causing your door to fall in during firing. People were not meant to
> live that far north.
>
> Okay, now for a serious answer. With only 5" of thickness, I expect that
> your homemade castable is shrinking on the inside surface where it is
> getting hottest, causing the door to lean inwards during the firing.
> That's
> one of the disadvantages of homemade castable. What recipe did you use?
> With door blocks only 5" thick, I don't think that there is any way to
> avoid
> this. As I see it, you have three choices. First you could cast thicker
> door blocks from your homemade castable, so that they will be more stable
> during the firing. Second you could brick up the door with 9" of standard
> hardbrick, with frequent header courses tying together the two layers of
> hardbrick. Third, you could make a modular fiber door, but I would be
> worried about carcinogenic fibers floating around whenever you move the
> door.
>
> I hope this helps -
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft
> Tennessee Tech University
> vpitelka@dtccom.net; wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka
>
Snail Scott on sun 16 nov 08
On Nov 16, 2008, at 1:05 PM, Vince Pitelka wrote:
> The problem is that in South Dakota, the horizontal circumference of
> the
> earth is less, and therefore the centrifugal force is far greater, and
> this
> is causing your door to fall in during firing...
No, no, no! Centripetal force is reduced as
radius diminishes. All kilns rely on that force to
keep their doors from falling inward; it's the lack
of sufficient force in the Great White North (or South)
that causes it to fall. That's why top-loading kilns are
mostly round: no door, so every part of the kiln is
equally affected. It's a door thing. That's why tropical
huts don't have them - too much centripetal force.
In seriousness, perhaps you could try shimming the
door between courses. It would lean a bit outward
initially, then as firing progressed, straighten up.
Maybe?
-Snail
Vince Pitelka on mon 17 nov 08
Larry wrote:
"I know this might throw a wrench into the works. ceramic material such as
fire brick or castables do not shrink they expand when temperature is
increased."
Larry -
In general things do expand when they are heated, but one of the big
problems with some homemade castable refractories as were used in this case
is that they flux excessively and shrink a great deal when fired to
maturity, and these sorts of problems are not uncommon. That's why we pay
the price for the commercial products. The homemade door blocks might
expand a little initially, but when the fluxes kick in they shrink a lot on
hotface, thus the problem that was described.
A stacked hardbrick door that is nine inches thick with a good mix of
stretcher and header courses needs no exterior frame. If it is built of
quality hardbrick, coated on the contact faces with shelf wash, and if the
outside surface is sealed with a wadding made from equal parts recycle
slurry, flint, and sand, there will be very little shifting and movement in
the door, and minimal gaps will open up. Of course the reality is that a
stacked hardbrick door is impractical except with a salt or soda kiln,
because it is a huge thermal mass that absorbs a great deal of heat - far
more than what is required to fire the wares. I like the idea of door
blocks made from homemade insulating castable, but they have to be made
thick enough to be stable, and they should be high-fired in another kiln
before they are used. That will eliminate most of the shrinkage problems.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
larry on mon 17 nov 08
I know this might throw a wrench into the works. ceramic material such as
fire brick or castables do not shrink they expand when temperature is
increased. I remember a 250 cu ft homemade kiln I had that used no arch
brick as it heated up you could literally slide something that was 1/4 inch
between the bricks. As the kiln cooled individual bricks would slide down
as the kiln settled back into position. The same principle happens with
stacked doors since there is no outside frame to hold it in place the heat
builds up tremendous prressure against the brick and the weakest location
gives way. If your arch kiln has no outside frame you might solve the
problem by building a frame with chain tensioners to hold consistent
pressure against the brick. This will also make the kiln more efficient as
not as much heat will be lost through the gaps in the brick. Just my
thoughts. Larry
----------------------------------------
From: "Vince Pitelka"
Sent: Sunday, November 16, 2008 12:44 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: bricks falling in -in a brick up door...
Pat in SD wrote:
"Last night- the firing was going well, cone 9 was on
the way down on one side, cone 8 was softening on the other side- I
wandered
into the studio for a bit and when I came back outside to check the cones-
they were gone on one side (my first clue something was wrong), and by
pulling back the fastening on the door an inch, I could see that the top
few
bricks of the arch had fallen in. Looking in the peephole confirmed that
pots were laying on their sides and tipped. Ugh!
Pat -
The problem is that in South Dakota, the horizontal circumference of the
earth is less, and therefore the centrifugal force is far greater, and
this
is causing your door to fall in during firing. People were not meant to
live that far north.
Okay, now for a serious answer. With only 5" of thickness, I expect that
your homemade castable is shrinking on the inside surface where it is
getting hottest, causing the door to lean inwards during the firing.
That's
one of the disadvantages of homemade castable. What recipe did you use?
With door blocks only 5" thick, I don't think that there is any way to
avoid
this. As I see it, you have three choices. First you could cast thicker
door blocks from your homemade castable, so that they will be more stable
during the firing. Second you could brick up the door with 9" of standard
hardbrick, with frequent header courses tying together the two layers of
hardbrick. Third, you could make a modular fiber door, but I would be
worried about carcinogenic fibers floating around whenever you move the
door.
I hope this helps -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
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