Paul Haigh on wed 20 jan 10
I've tried maybe 4-5 configs for bourry firebox covers- heavy sheet metal w=
ith fiber insulation (sheet metal corrodes in 1-2 firings), 1/4" steel warp=
s, fiber board ends up getting banged up and breaking apart.
Latest idea: a channel iron frame with 2 kiln shelves set in it, backed wit=
h fiber insulation. I'll use cordeirite or high alumina. I figure if it wor=
ks to shove one of these cold into my chimney half way at 2200F, then it's =
got good thermal shock properties. I am curious if I will need ITC on the u=
nderside to reduce any warping, and if the ITC will hold up to a couple of =
scrapes with misplaced firewood.
Thanks,
-pH
http://wileyhill.com
David Hendley on thu 21 jan 10
Paul, I've found that kiln shelves have poor thermal shock qualities.
I used 2 hi-alumina shelves as the floor of my wood-fired bread
oven and they broke after a few uses. After a dozen "firings", both
are now in 4 pieces. In use, this involved starting a fire directly on
the shelves and slowly building up the oven to about 750 degrees.
I tried using a 12 X 24 silicon carbide shelf as a sliding door for
my passive damper and it was broken in lots of pieces after only
a few firings. The shelf was not inserted into the flame path, it
only blocked off the hole in the chimney. It did become a dull
glowing red when the kiln was clammed up for cooling.
I don't know what it is about these applications that is so hard
on kiln shelves - thermal shock? uneven heating?
David Hendley
david@farmpots.com
http://www.farmpots.com
----- Original Message -----
> I've tried maybe 4-5 configs for bourry firebox covers- heavy sheet metal
> with fiber insulation (sheet metal corrodes in 1-2 firings), 1/4" steel
> warps, fiber board ends up getting banged up and breaking apart.
>
> Latest idea: a channel iron frame with 2 kiln shelves set in it, backed
> with fiber insulation. I'll use cordeirite or high alumina. I figure if i=
t
> works to shove one of these cold into my chimney half way at 2200F, then
> it's got good thermal shock properties. I am curious if I will need ITC o=
n
> the underside to reduce any warping, and if the ITC will hold up to a
> couple of scrapes with misplaced firewood.
>
> Thanks,
> -pH
> http://wileyhill.com
Steve Mills on thu 21 jan 10
Paul,
We've used standard type thick kiln shelves or a kiln shelf-fibre-kiln shel=
f
sandwich as lids for our cross-draught wood kilns for years, and we fire
that sucker to ^12 no problems.
We also used 2 standard 3/4 inch shelves for the lid of Kusakabe-Sensei's
outsize Bourry box at the Aberystwyth Festival in Wales last July. Again, n=
o
problem.
It's the best answer.
Steve M
2010/1/20 Paul Haigh
> I've tried maybe 4-5 configs for bourry firebox covers- heavy sheet metal
> with fiber insulation (sheet metal corrodes in 1-2 firings), 1/4" steel
> warps, fiber board ends up getting banged up and breaking apart.
>
> Latest idea: a channel iron frame with 2 kiln shelves set in it, backed
> with fiber insulation. I'll use cordeirite or high alumina. I figure if i=
t
> works to shove one of these cold into my chimney half way at 2200F, then
> it's got good thermal shock properties. I am curious if I will need ITC o=
n
> the underside to reduce any warping, and if the ITC will hold up to a cou=
ple
> of scrapes with misplaced firewood.
>
> Thanks,
> -pH
> http://wileyhill.com
>
--
Steve
Bath
UK
www.mudslinger.me.uk
wileyhill on thu 21 jan 10
Excellent! I had some suggestions for doors that work for other people, =
=3D
but I know I'll have errant branches ripping out fiber pieces for most =3D
solutions. I'll use the shelves.
----- Original Message -----=3D20
From: Steve Mills=3D20
To: wileyhill@comcast.net=3D20
Cc: Clayart@lsv.ceramics.org=3D20
Sent: Thursday, January 21, 2010 6:01 PM
Subject: Re: The latest Bourry Box cover: shelves and ITC
Paul,
We've used standard type thick kiln shelves or a kiln shelf-fibre-kiln =
=3D
shelf sandwich as lids for our cross-draught wood kilns for years, and =3D
we fire that sucker to ^12 no problems.
We also used 2 standard 3/4 inch shelves for the lid of =3D
Kusakabe-Sensei's outsize Bourry box at the Aberystwyth Festival in =3D
Wales last July. Again, no problem.
It's the best answer.
Steve M
2010/1/20 Paul Haigh
I've tried maybe 4-5 configs for bourry firebox covers- heavy sheet =3D
metal with fiber insulation (sheet metal corrodes in 1-2 firings), 1/4" =3D
steel warps, fiber board ends up getting banged up and breaking apart.
Latest idea: a channel iron frame with 2 kiln shelves set in it, =3D
backed with fiber insulation. I'll use cordeirite or high alumina. I =3D
figure if it works to shove one of these cold into my chimney half way =3D
at 2200F, then it's got good thermal shock properties. I am curious if I =
=3D
will need ITC on the underside to reduce any warping, and if the ITC =3D
will hold up to a couple of scrapes with misplaced firewood.
Thanks,
-pH
http://wileyhill.com
--=3D20
Steve
Bath
UK
www.mudslinger.me.uk
wileyhill on thu 21 jan 10
I use a high alumina shelf for a damper and haven't had any issues- not sur=
e
why it would be less stress than starting a fire directly on one though.
SiCarb is supposed to be particularly thermal shock sensitive.
Because I'd be raising temp in the firebox rather than putting them right
into a fire from cold, I'd guess they would have less issue than starting a
fire on one. Steve Mills has experience using shelves as firebox lids and
they were robust, it seems.
----- Original Message -----
From: "David Hendley"
To: ;
Sent: Thursday, January 21, 2010 9:09 PM
Subject: Re: The latest Bourry Box cover: shelves and ITC
> Paul, I've found that kiln shelves have poor thermal shock qualities.
> I used 2 hi-alumina shelves as the floor of my wood-fired bread
> oven and they broke after a few uses. After a dozen "firings", both
> are now in 4 pieces. In use, this involved starting a fire directly on
> the shelves and slowly building up the oven to about 750 degrees.
>
> I tried using a 12 X 24 silicon carbide shelf as a sliding door for
> my passive damper and it was broken in lots of pieces after only
> a few firings. The shelf was not inserted into the flame path, it
> only blocked off the hole in the chimney. It did become a dull
> glowing red when the kiln was clammed up for cooling.
>
> I don't know what it is about these applications that is so hard
> on kiln shelves - thermal shock? uneven heating?
>
> David Hendley
> david@farmpots.com
> http://www.farmpots.com
>
>
>
> ----- Original Message -----
>
>> I've tried maybe 4-5 configs for bourry firebox covers- heavy sheet meta=
l
>> with fiber insulation (sheet metal corrodes in 1-2 firings), 1/4" steel
>> warps, fiber board ends up getting banged up and breaking apart.
>>
>> Latest idea: a channel iron frame with 2 kiln shelves set in it, backed
>> with fiber insulation. I'll use cordeirite or high alumina. I figure if
>> it works to shove one of these cold into my chimney half way at 2200F,
>> then it's got good thermal shock properties. I am curious if I will need
>> ITC on the underside to reduce any warping, and if the ITC will hold up
>> to a couple of scrapes with misplaced firewood.
>>
>> Thanks,
>> -pH
>> http://wileyhill.com
>
Eva Gallagher on fri 22 jan 10
Well I have been disappointed with using kiln shelves as the lids for the
train portoin of my train kiln. Though I only fired it once, about 4 of the
8 shelves developed hairline cracks where they rested on the side walls of
the kiln. They overlapped the sides by 3" and as the sides are made out of
insulating bricks then I have to conlcude that there was just too much
temperature difference near the ends of the shelves. I plan to replace the
top row with hard bricks hoping this will even out the temp a bit.
For my bourry box lid I used 2 layers of fiberboard held in an angle iron
frame. I also ITC everything - the shelves as well as the boards.
Eva Gallagher
Deep River, Ontario
http://stevenhilljourneyworkshopjuly2008.blogspot.com/
----- Original Message -----
From: "wileyhill"
To:
Sent: Thursday, January 21, 2010 7:35 PM
Subject: Re: The latest Bourry Box cover: shelves and ITC
Excellent! I had some suggestions for doors that work for other people, bu=
t
I know I'll have errant branches ripping out fiber pieces for most
solutions. I'll use the shelves.
----- Original Message -----
From: Steve Mills
To: wileyhill@comcast.net
Cc: Clayart@lsv.ceramics.org
Sent: Thursday, January 21, 2010 6:01 PM
Subject: Re: The latest Bourry Box cover: shelves and ITC
Paul,
We've used standard type thick kiln shelves or a kiln shelf-fibre-kiln
shelf sandwich as lids for our cross-draught wood kilns for years, and we
fire that sucker to ^12 no problems.
We also used 2 standard 3/4 inch shelves for the lid of Kusakabe-Sensei's
outsize Bourry box at the Aberystwyth Festival in Wales last July. Again, n=
o
problem.
It's the best answer.
Steve M
Ron Roy on sat 23 jan 10
Hi David,
I'm sure it has a lot to do with expansion and contraction - imagine
what happens when part of a shelf goes through a quartz or a
cristobalite inversion for instance.
I'm also sure that using a shelf made of material that has a low
expansion will do much better.
Finding the shelf with the lowest expansion rate would be a step in
the right direction. Any one have some samples for me to measure in my
dilatometer?
RR
Quoting David Hendley :
> I don't know what it is about these applications that is so hard
> on kiln shelves - thermal shock? uneven heating?
>
> David Hendley
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