T Robert on tue 30 jan 07
There have been a number of postings to Clay Art recently regarding
shipment of Nitride Bonded shelves from Axner /Laguna.
Like any and all company=92s who utilize services to ship merchandise,
there are occasions where items arrive damaged. This has been
extremely rare with Axner / Laguna due to our vast experience in
packing and shipping. Nonetheless, we will continue examining our
packing and shipping methods in order to improve standards when
and where essential.
Meanwhile, the original complaint posted, regarding shelves breaking
after being fired, and attributed to shipping, has been researched.
After learning the atmosphere and firing schedule of the shelves in
question, it has been determined that the breakage was due to use of
vent and crash cooling method in a radiantly heated (electric) kiln.
Nitride Bonded shelves have a high thermal expansion and are most
sensitive to thermal shock in fast firing and or cooling applications.
This is much more so the case in a radiantly heated kiln. Heat
transfer begins at the heat source (elements) and moves to the
coolest point (the center). When you have a solid 1-piece shelf with
little porosity and high thermal expansion, it will experience a sizeable
differential temperature between the perimeter and center. In addition
the use of a vent/ fan should be discouraged as it is drawing cool air
in and along the edges of the wide flat shelves while the center
remains hot. Even using precautions during quartz conversion
portions of the firing, the Nitride bonded shelves (or any other shelves
for that matter) are susceptible to cracking and breaking using fast
firing and cooling methods in a radiantly heated environment.
The advantages of using the nitride-bonded shelves are with out
question excellent. However, those persons using them in
oxidation/electric kilns must be aware of issues regarding high
thermal expansion and heat transfer and adjust their firings
accordingly.
Thank you for your time and consideration.
T. Robert
Axner Laguna
Production Manager
Resident Potter
Kathi LeSueur on tue 30 jan 07
T Robert wrote:
>There have been a number of postings to Clay Art recently regarding
>shipment of Nitride Bonded shelves from Axner /Laguna......
>
>the original complaint posted, regarding shelves breaking
>after being fired, and attributed to shipping, has been researched.
>After learning the atmosphere and firing schedule of the shelves in
>question, it has been determined that the breakage was due to use of
>vent and crash cooling method in a radiantly heated (electric) kiln.
>
>Nitride Bonded shelves have a high thermal expansion and are most
>sensitive to thermal shock in fast firing and or cooling applications.
>This is much more so the case in a radiantly heated kiln. Heat
>transfer begins at the heat source (elements) and moves to the
>coolest point (the center). >>>>
>
Since I'm considering buying these shelves to use in my gas kiln, which
I fire to Cone 10, I would be interested to see your recommendation for
a firing schedule. My kiln heats up rapidly, 1000 degrees in 3 hours.
I've never had a problem with corderite shelves (except the thirteen I
bought after Thorely was bought by Laguna).
So please, what is a proper firing schedule. Cooling isn't a problem
since I don't touch the kiln until it hits 300 degrees.
Kathi
Paul Borian on tue 30 jan 07
i have a some questions about this for anyone who may know the answers.
first of all, do regular silicon carbide shelves have a similarly high
thermal expansion as the nitride bonded?
Also, would they be suspectible to cracking during a rapid heatup in a gas
kiln? My kiln cools very slow so that is not an issue, but the ambient temp
inside the kiln jumps very fast when i light the first burner. Of course,
the ware and shelves are not heating up nearly as fast at the pyrometer
thermocouple, but the time it takes to get a reading of 1000 F is less than
two hours. Would this be likely to crack regular silicon carbide shelves? I
need to know because i just ordered a new set of them.
What is the max rate of climb in this type of kiln then can handle?
thanks,
Paul
Lee Love on wed 31 jan 07
On 1/31/07, Paul Borian wrote:
> i have a some questions about this for anyone who may know the answers.
>
> first of all, do regular silicon carbide shelves have a similarly high
> thermal expansion as the nitride bonded?
I don't think so. My wood kiln heats rapidly and I crash cool
at the end of firing, from 1300*C to 1100*C. Never had any
problems. Mine are pretty thin and light. My last dozen I bought
used for about $8.50 each. The factories in Seto replace their kiln
shelves according to a time schedule, whether they are "worn" or not.
My supplies guy picks out the best ones for us and delivers them to
Mashiko. He visits a couple times a month. I can in no way see how
the fragile nitride bonded shelves could replace them economically.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://potters.blogspot.com/
"Let the beauty we love be what we do." - Rumi
"When we all do better. We ALL do better." -Paul Wellstone
William & Susan Schran User on wed 31 jan 07
On 1/30/07 7:53 PM, "Paul Borian" wrote:
> but the time it takes to get a reading of 1000 F is less than
> two hours. Would this be likely to crack regular silicon carbide shelves? I
> need to know because i just ordered a new set of them.
> What is the max rate of climb in this type of kiln then can handle?
> thanks,
We use Advancers, silicon carbide and cordierite shelves in our ^10 firings,
heating at the same rate as out wrote.
Have not had any problems with cracking/breaking.
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Deborah Woods on fri 2 feb 07
Hello everyone. My input on this subject is this. As some may remember, I
had some problems with corderite shelves from Laguna. I finally gave up
and ordered the silicon carbide shelves from Bailey Pottery in New York.
From my experience by the way, you can't go wrong with this company. Great
customer service so far. So anyway, after loosing about 9-12 (can't
remember) brand-new Laguna corderite shelves on their first firing (no, no
crash cooling, I fire down with my computer), I am quite happy with the
new type shelves. One interesting note, the shelves seem to affect my clay
body. It is noticeably darker on the pots fired on these shelves. It was
funny, because I had a bird-bath on one level, and the bottom is two
different colors because I had one new shelf on one half of the kiln, and
a corderite shelf on the other half. But, all I know is that they went
through their first firing to cone 6 without cracking or breaking in half.
This is historic in my studio. They were packed really well from Bailey as
well, and while I can't promise you the same results as far as shipping,
they got to me in an amazing day and a half. I think they were really
trying to help me out because I was in a bind, but that just says more
good things about the company.
Deborah Woods
jupitersmoonpottery.com
Jennifer Boyer on sat 3 feb 07
I had a similar experience when starting to use new Nitride Bonded
shelves from New Castle http://www.ncrci.com/ in Pennsylvania years
ago. The first firing produced a local reduction area that darkened
the bottoms of pots on the new shelves. This was only in the first
firing and after that all went back to normal.
I'm in need of some new shelves and am watching this shelf dialogue
with interest.
Jennifer
On Feb 2, 2007, at 9:35 PM, Deborah Woods wrote:
> One interesting note, the shelves seem to affect my clay
> body. It is noticeably darker on the pots fired on these shelves.
> It was
> funny, because I had a bird-bath on one level, and the bottom is two
> different colors because I had one new shelf on one half of the
> kiln, and
> a corderite shelf on the other half.
> Deborah Woods
> jupitersmoonpottery.com
>
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*****************************
Jennifer Boyer
Thistle Hill Pottery
Montpelier, VT
http://thistlehillpottery.com
*****************************
Anne Webb on thu 12 apr 07
HiWe are looking to get new shelves for our gas kiln. Many firings, good an=
d bad, have taken a hard toll on the ones we have. The shelves are so warpe=
d (you would not believe how warped..like 2" sag on some of them in the mid=
dle... ) that I have to wad every single pot that goes in. Lots of kiln spa=
ce wasted. They are also heavy and quite unwieldy when i have to reach in a=
nd load
them into the back of the kiln lengthwise (leverage prob my back
doesn't like) and needless to say, with the warp and placement in the kiln =
(lengthwise) I can't leave those shelves in the back in the kiln at set lev=
els to load around. With the ever rising cost of propane i need to get tha=
t many more pots in the kiln. Whine whine whine.Well the ole tax refund has=
finally arrived and I have been looking around for shelves.. wouldnt you s=
ay its about time?? what is the difference between the Advancer nitride-bo=
nded silicon carbide shelves and other nitride bonded silicon carbide shel=
ves? ...besides the considerable price difference, I mean. Does anyone her=
e know?Any feedback about this kind of shelf?(FYI still playing around with=
those celadons, for all of you who emailed me about them. )This might be a=
good on-list topic, but if you choose to email me offlist, please send you=
r email to me at webbpottery@gulftel.com.Have a great day!Anne
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William & Susan Schran User on thu 12 apr 07
On 4/12/07 10:00 AM, "Anne Webb" wrote:
> what is the difference between the Advancer nitride-bonded silicon carbide
> shelves and other nitride bonded silicon carbide shelves? ...besides the
> considerable price difference, I mean. Does anyone here know?Any feedback
> about this kind of shelf?
Anne,
There was a lengthy thread on this not too long ago, so a search of the
archives will answer many of your questions.
Briefly, the difference is you get what you pay for. The shelves use
different quality of materials, are formed differently and are fired
differently. The Advancers have a >1% absorption rate, thus no kiln wash is
needed and the other nitride bonded shelves have about a 15% absorption,
about the same as regular silicon carbide shelves, so kiln wash would
probably be needed.
Have 20 Advancers for our gas fired kiln at school (fifing to cone ten).
They have suffered the indignities of student glazing issues and are
performing wonderfully.
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
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