Eleanora Eden on fri 13 dec 96
Hi all,
I don't remember anybody mentioning Norton Co in Norton, MA as a good
source of cheap silicon carbide shelves. Now it has been 25 years or so
since I was in the market for these shelves on the east coast but way
back when I used to have a real friendly relationship with a guy who was
in charge of finding homes for over-production of silicon carbide shelves
at Norton Co. He kept an updated list of overruns and sent it to me when
I'd ask.
Since I could drive down from Vermont this made the whole thing ideal for
a small studio. Before I built or furnished a kiln I'd get in touch and
see what he could supply.
Eleanora
Eleanora Eden 802 869-2003
Paradise Hill
Bellows Falls, VT 05101 eden@maple.sover.net
[the address fga@world.std.com is temporary. My mailbox at
eden@maple.sover.net still works -- do not change address books]
Laura Conley on tue 3 feb 98
I am in the process of purchasing an electric kiln and am wondering about shelve
I have recently become aware of the silicon carbide variety that are much lighte
(and more fragile, and shouldn't go in the kiln wet, etc.). Do these come in t
shapes for electric kilns? If so, should I get these instead of mullite? I kno
they are more expensive - are they worth it?
Thanks, Laura Conley
Boulder, CO
Lili Krakowski on thu 5 feb 98
One of our more scientific members can explain why--but suffice it to say
NO SILICON CARBIDE SHELVES IN AN ELECTRIC KILN. The one time silicon
carbide is used in electric kilns is in glazes that have tiny tiny amounts
to creat local
reduction. Which read up on in the literature. DO NOT get silicon
carbide shelves for your electric kiln.
On Tue, 3 Feb 1998, Laura Conley wrote:
> ----------------------------Original message----------------------------
> I am in the process of purchasing an electric kiln and am wondering about shel
> I have recently become aware of the silicon carbide variety that are much ligh
> (and more fragile, and shouldn't go in the kiln wet, etc.). Do these come in
> shapes for electric kilns? If so, should I get these instead of mullite? I k
> they are more expensive - are they worth it?
>
> Thanks, Laura Conley
> Boulder, CO
>
Lili Krakowski
Chris Hogg on sun 4 apr 99
Traditional silicon carbide refractories are clay-bonded. This is
because silicon carbide is very difficult to sinter on its own, and a
mix of clay and silicon carbide grain is used. These refractories are
quite porous, and air can readily penetrate the structure. In use, the
grains of silicon carbide progressively oxidise to silica at
temperatures in the range 1000C to 1300C, typical of studio pottery kiln
temperatures. Reduction firing at these temperatures will not slow this
oxidation very much. Silicon carbide is made by heating a mixture of
coke and silica sand in an electric arc furnace. The temperatures and
strength of reduction are _very_ much greater than can be achieved in a
studio kiln. At lower temperatures and under less-strong reduction, the
reaction reverses and silica is formed.
Oxidation of the silicon carbide brings two problems. First, silica is
less dense than silicon carbide, which means that as they oxidise, the
silicon carbide grains grow, causing internal stresses within the
refractory structure. Second, the silica that forms is usually
cristobalite, i.e. that form of silica with a very high thermal
expansion coefficient. Repeated cycling through the critical temperature
region of 250 to 300C (where the biggest expansion/contraction occurs)
as inevitably happens with intermittent kilns, creates further stresses.
The combined stresses of oxidation and thermal expansion mean that
silicon carbide refractories have a fairly short life, and distortion,
cracking and premature failure are to be expected.
It is possible to prolong the life of silicon carbide refractories by
coating them with an impermeable layer, rather like a vitreous engobe,
but this usually has to be done during manufacture. Improved silicon
carbide refractories are also now available, such as nitride-bonded
silicon carbide, silicon infiltrated silicon carbide and dense sintered
silicon carbide. They are very expensive and probably not worth the
outlay for the studio potter.
Chris.
Joyce Lee on wed 7 apr 99
I was under the illusion that silicon carbide shelves were about the
best. Is this wrong? Important because I'm in the process of ordering a
set for my new, as yet unarrived, Geil salt/soda kiln. Would they
benefit from being ITCed also? What are the best shelves for such
firings? Thank you.
Joyce
In the Mojave trying to find something good to say about the despicable,
eerie, anthropomorphic wind (can "wind" be classified as an "animal"?
What's the word for things in nature, not animals, being given human
qualities?) .....well, it'll be over soon...that's good.
Chris Hogg on thu 8 apr 99
Joyce Lee wrote:
>
> ----------------------------Original message----------------------------
> I was under the illusion that silicon carbide shelves were about the
> best. Is this wrong? Important because I'm in the process of ordering a
> set for my new, as yet unarrived, Geil salt/soda kiln. Would they
> benefit from being ITCed also? What are the best shelves for such
> firings? Thank you.
Joyce,
I have no experience of silicon carbide in salt firing. My comments
related to their use in conventional circumstances. I would imagine in
salt firing, the glassy coat that soon covers everything could seal the
surface of the shelves etc. quite effectively and slow up their rate of
oxidation.
Chris.
Joyce Lee on fri 9 apr 99
Thank you, Clayarters, for giving me plenty of information about the
silicon carbide shelves and enabling me to avoid a costly mistake. Most
of you agreed that the shelves are too heavy, oxidize easily and often
warp, but usually crack before warping occurs. Apparently, they're very
strong BUT brittle and may crack from thermal "tension." Must be the
carbide, huh? Like my newish Bison tools that are tungsten carbide and
very strong, but must be babied because they, too, are "brittle" and
break if dropped on the concrete...they're wonderful tools, though, and
their handling CAN be controlled. Can't imagine being able to exert that
kind of "control" over the silicon carbide shelves INSIDE the firing
kiln. Right now, the aluminous (???..I know I have the suffix wrong
here) shelves from England seem to be a good choice, and are even a
little less expensive than the silicon carbide. They'll be treated with
ITC, of course......thanks to all my experienced and generous advisers
on Clayart.
Joyce
In the Mojave loving the look of the snow on the Sierras out the front
window...looks like you could reach out, grab some and make snowcream.
Judy Weeden on sun 11 apr 99
Hi Joyce, Chris,
I have had my silicon carbide kiln shelves for 20 years. They have been
fired at least 500 times,probably more. I use them in my electric kiln at
cone 06 bisque and cone 10 glaze. They are coated with ordinary commercial
kiln wash. They have not cracked, warped, shrunk, or whistled dixie. They
have even survived a kiln disaster wherein my mullite shelves gave up the
ghost.
I have been told that I should not be using silicon carbide shelves in an
electric kiln because they will conduct electricity. I have not heeded that
advice. But I am very careful about how I load my kilns, and I keep my
kilns in good repair. There are no sick elements hanging out of their
grooves.
I do not wish to dispute your scientific knowledge about silicon carbide,
Chris. It is just something that I have not experienced in practise, and I
am blissful in my ignorance of 20 years. Judy
Judy Weeden
weeden@saltspring.com
Donn Buchfinck on sun 11 apr 99
Joyce,
I just wanted to drop a line and say that silicon carbide shelves are the
best to have.
I have used both types of shelves, silicon carbide and the thorly, and the
clay shelves wear out faster. In the long run you will have to purchase
shelves again.
I have seen shelves in use for 20 years that show little wear. It is how you
use them. If you are in a school situation the clay shelves are the best
because some breakage will occur. But I saw shelves at Penn St. that lasted
quite a long time. They used 9 inches by 24 inches and these worked great.
silicon carbide is great stuff. It gets stronger the hotter it gets. And I
have seen cracks though a kiln shelf that is there for years that last a long
time without breaking.
I think firing with silicon carbide shelves in a salt kiln and wood kiln is
better. For some reason it gives great flashing, and in a salt kiln you get
these real cool crystals that grow on the bottom of the shelves.
If cost is a problem, just make sure the clay shelves you buy will not dunt
in the kiln after you salt fire them. Some of the high alumina shelves have
been known to do this.
and finally what makes a kiln shelf warp is the kiln wash on the shelf.
Good luck
Donn Buchfinck
Joyce Lee on mon 3 jan 00
This is in response to Mike's query to owners of Geil fiber-lined kilns,
who have sprayed the fiber with ITC. I have sprayed both my fiber kilns
(Geil) with ITC, following closely the directions sent by the company.
I've had no problems with the use of the ITC. I sprayed the electric
kiln also.... no problems. I also sprayed shelves, elements etc...
again, no problems. In addition, my firings seem more even top to
bottom, front to back, since spraying.
Joyce
In the Mojave not liking the wind... so eerie, foreboding sounding....
and unceasing early morning... can't even see the Sierras for the
salts/sand being stirred up...
Gwyn Ace on thu 8 jun 00
As I understand..Silicon Carbide shelves are best not used in
an Electric Kiln as they conduct power and we all know how=20
elements can buckle and droop and other bad habits so that
they can present an electrical hazard.
Best to stick to shelves which cannot be a potential danger
Gwyn in N.Z.
iandol on tue 9 jan 01
Dear Bob,
I can't answer that question. Perhaps it is another of those Myths.
Perhaps I should have pointed out that Silicon Carbide tends to oxidise =
at high temperatures. Chemical breakdown leaves a film of silica, =
presumably as a glass, which forms a self preserving surface. Fused =
silica would act as an insulator.=20
Ivor.
Gwyn Ace on mon 2 jul 01
No..I haven't tried cutting it because as silicon carbide is so hard =
that it is of course..used as an abrasive and probably the only thing =
would cut it would be a diamond saw .. and the wear of the diamond saw =
blade could be such that it would pay for a couple of silicon carbide =
shelves... GWYN in N.Z.
.........with a few shelves I would like to cut if only it were =
possible !!!!
Marcia Selsor on mon 2 jul 01
You can cut a silicon carbide shelfe with a mason chisel. Put it on a
bag of clay. Tap a score line where the cut is to be with a 3.5" -5"
mason chisel. Then notch each edge with the chisel. Then keep tapping
the line. eventually you can wack it and it will snap.
If this is not appealing, take it to a grave stone shop. They may be
able to cut it for you.
Marcia in Montana
Gwyn Ace wrote:
>
> No..I haven't tried cutting it because as silicon carbide is so hard that it is of course..used as an abrasive and probably the only thing would cut it would be a diamond saw .. and the wear of the diamond saw blade could be such that it would pay for a couple of silicon carbide shelves.. GWYN in N.Z.
> ..........with a few shelves I would like to cut if only it were possible !!!!
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
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>
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--
Marcia Selsor
selsor@imt.net
http://www.imt.net/~mjbmls
http://www.imt.net/~mjbmls/Tuscany2001.html
http://www.imt.net/~mjbmls/Gallery.html
Betsy Cox on thu 3 jan 02
I recently acquired some silicon carbide shelves , but was told to only =
use them in a reduction firing that an oxidation firing would cause =
them to disintegrate .So i will ask all the experts on this list. Thanks =
in advance . Betsy=20
David Hendley on fri 4 jan 02
In a word, balderdash.
Silicon Carbide shelves are great and will serve you well for a long time
regardless of firing atmosphere.
Perhaps your source was equating 'oxidation firing' with 'electric kiln
firing'.
I have heard that it is not advisable to use silicon carbide shelves in an
electric kiln because they conduct electricity, and could cause problems if
they accidentally come in contact with the kiln elements.
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com
----- Original Message -----
From: "Betsy Cox"
To:
Sent: Thursday, January 03, 2002 7:29 AM
Subject: silicon carbide shelves
I recently acquired some silicon carbide shelves , but was told to only use
them in a reduction firing that an oxidation firing would cause them to
disintegrate .So i will ask all the experts on this list. Thanks in advance
. Betsy
__________
.
Steve Mills on sat 5 jan 02
I have also had this warning.
Makes sense.
Steve
Bath
UK
In message , David Hendley writes
>I have heard that it is not advisable to use silicon carbide shelves in a=
>n
>electric kiln because they conduct electricity, and could cause problems =
>if
>they accidentally come in contact with the kiln elements.
>
>David Hendley
>Maydelle, Texas
>hendley@tyler.net
>http://www.farmpots.com
>
--
Steve Mills
Bath
UK
Curtis Nelson on sat 5 jan 02
David Hendley wrote:
I have heard that it is not advisable to use silicon
carbide shelves in an
electric kiln because they conduct electricity, and
could cause problems if
they accidentally come in contact with the kiln
elements.
----------------------------
Since David has heard this and has taken the time to
post it yesterday, I take notice. Can anyone comment
with certainty as to the validity of what he has only
heard?
Ciao -
Curt Nelson
Dewitt on sat 5 jan 02
At 21:17 1/5/02 -0500, you wrote:
>Since David has heard this and has taken the time to
>post it yesterday, I take notice. Can anyone comment
>with certainty as to the validity of what he has only
>heard?
If you do a search on www.google.com for "silicon carbide kiln elements"
you'll find links that talk about using silicon carbide heating elements in
electric kilns. That should confirm David's comment that they conduct
electricity.
deg
---------------------------
Dewitt Gimblet
dewitt@texas.net
Austin, TX
---------------------------
Jones Pottery on sun 6 jan 02
>
> I have heard that it is not advisable to use silicon
> carbide shelves in an
> electric kiln because they conduct electricity
I use silicon carbide shelves in an electric kiln during bisque firing. I
have NO problems so far after 3 years of firings. All is well for me and
this is only from my personal excperience. I never advocate doing what I do.
I am just passing on my experience.
Chris
Dave Murphy on tue 3 sep 02
Anyone out there know where we could lay our hands on some used silicon
carbide shelves for a salt kiln, size 14 X 28 or 12 X 26 or any configuation
that would equal those dimensions. The kiln has room for two stacks front
to back. Failing 2nd hand, where to find new ones (ouch!).
We just found out that the high alumina ones used in the reduction kiln will
resist the salt and not be successful. Any thoughts or experiences? TIA
David and Barbara Murphy
Waterloo County Pottery
Waterloo Ontario
Canada
Deeclay@AOL.COM on sat 5 oct 02
Hi everyone
Our potters guild in Broward County, Fl. is looking to buy silicon carbide
shelves 12"x24" the very thin ones. I think they are 1/4" thick. Does anyone
know where we can get them, new or used? We would like to get about 10.
Thanks for your help. Suppliers can contact me directly.
Diane in Sunny Miami
hmurrow@EFN.ORG on sun 6 oct 02
Quoting Deeclay@AOL.COM:
> Hi everyone
> Our potters guild in Broward County, Fl. is looking to buy silicon carbide
> shelves 12"x24" the very thin ones. I think they are 1/4" thick. Does
> anyone
> know where we can get them, new or used? We would like to get about 10.
> Thanks for your help. Suppliers can contact me directly.
> Diane in Sunny Miami
Dear Diane;
I believe that you would be well served by contacting Dona at Firebrick Supply
in Minneaplolis to get in on a group order for your size shelf. Recommend that
you look into Advancer shelves if budget permits. I LOVE mine.
Cheers, Hank
------------------------------------------------------------
Visit http://www.efn.org for all your community networking needs
Jeff Longtin on sun 6 oct 02
Diane/Hank,
As I always have a bitch of a time finding their number, and I'm just down
the street, I'll share this.
They're also known as Smith-Sharp/Firebrick supply.
Jeff Longtin
jim behan on sun 27 oct 02
Can someone provide reliable and proven information on
what type or 'bond' of silicon carbide shelving one
should get for use in a woodfired saltglaze kiln. I
would also welcome the name(s) of supliers in
UK/Europe.
Thank you all,
Jim Behan
=====
From : Jim Behan (Dolmen Pottery) 113, Green Rd., Carlow Ireland. e-mail dolmenpots@yahoo.com
website http://dolmenpottery.com
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Marilu Tejero on sun 6 mar 05
I've looked through the archives and can't find info about who sells them.
I need 10 24 1/2'' x 12".
Any advice about traders and prices would be much appreciated.
Thanks
Marilu
At NCECA please come to the International Artists slide show.
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