John Jensen on mon 18 mar 02
Is it the case that a "straight" brick used in an arch can be slid out,
where as a wedge cannot. I've only built one kiln, so I'm no expert. Maybe
it is the case that in practical fact those straights just don't ever shift,
or that if they do, they easily can be tapped back into place. But the
Larkin fellow was just saying that the wedge was inherently stable and
straights were not. It seemed to be the case that in his experience there
could be problems with the using straight. At least that's how I heard it.
John Jensen, Mudbug Pottery, Annapolis
mudbug@toad.net, www.Toadhouse.com
vince pitelka on wed 20 mar 02
> Is it the case that a "straight" brick used in an arch can be slid out,
> where as a wedge cannot. I've only built one kiln, so I'm no expert.
Maybe
> it is the case that in practical fact those straights just don't ever
shift,
> or that if they do, they easily can be tapped back into place. But the
> Larkin fellow was just saying that the wedge was inherently stable and
> straights were not. It seemed to be the case that in his experience there
> could be problems with the using straight. At least that's how I heard
it.
John -
I only heard about his talk second hand, because I was chained to my booth
in the exhibition hall. I think there is a widespread belief that straights
in an arch, especially in the upper portion of an arch, are somehow risky.
But there is no evidence of this in a properly made arch. I think that
problems occur when the arch is poorly built or supported, such as when the
lateral support is provided by tie rods with springs on them, which is a
very bad idea. I have never seen any problem with straights in a tight,
well-built arch, either IFBs or hardbrick. I have seen successful arches
built entirely out of straight bricks with an airset mortar filling the
spaces to achieve the necessary curvature. Jim Wunch is of course correct
that the arch/wedge bricks are inherently more stable, because weight and
movement simply cause them to wedge in tighter. I guess I would have to
agree that in the best possible situation an arch would be all arch/wedge
bricks. But as I said, in a well constructed arch I have never experienced
any problem with straight bricks shifting.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Marcia Selsor on tue 19 oct 04
I agree, Stagger the bricks. I have built a lot of sprung arch kilns
for the college and also in studios. I believe staggering gives you the
strongest arch. You can also use car valve springs on threaded rod on
each end of your arch. You can tighted up your arch as needed. The
valve springs let the arch expand and contract under pressure. I also
love when the arch support comes out and there you have it! - a
standing arch.
To cut the bricks ( if you are using hard bricks).
knick each corner midway, score in the middle on all four sides and
then give it a hard whack. You can get pretty clean breaks on a hard
brick that way.
Marcia Selsor
On Oct 19, 2004, at 6:26 PM, Steven Goldate wrote:
> Hi Folks,
>
> I'm currently building a new 4 port downdraught gas kiln. A friend who
> is
> quite a knowledgeable kiln builder wants to offset the arch bricks by
> half a
> brick, so they are staggered and 'interlocked'. He says this will give
> the
> arch greater strength. However, I'm only familiar with the simpler
> method of
> just placing them in simple rows. Has anyone got any advice on this?
>
> Thanks,
> Steven
>
> -------------------------------------------------------------------
> Steven Goldate, Editor, Ceramics Today
> http://www.ceramicstoday.com
> Encyclopaedia of Ceramic Artists
> http://ceramicsdictionary.com
> sgoldate@bigpond.net.au; sgoldate@aasb.com.au
> -------------------------------------------------------------------
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
Gary Navarre on tue 19 oct 04
"Steven Goldate"
Tue, October 19, 2004 7:26 pm asked:
Hi Folks,
I'm currently building a new 4 port downdraught gas kiln. A friend who is
quite a knowledgeable kiln builder wants to offset the arch bricks by half
a brick, so they are staggered and 'interlocked'. He says this will give
the arch greater strength. However, I'm only familiar with the simpler
method of just placing them in simple rows. Has anyone got any advice on
this?
Thanks,
Steven
Hay Steve, Crew,
Overlapping 1/2 brick is basic to brick laying. Every other course cut a
brick in half to fill in the ends. Walls have stringer courses but most
arches don't need them.
G. in Da U.P.
Navarre Pottery
Norway, Michigan, USA
Mark Knott on tue 19 oct 04
> steve, begining every other row with a 1/2 brick will give you a locked arch. far stronger than not stagering the seams. i believe the term to be a bonded arch. you can also use 13 1/2 inch bricks and full bricks which will give even less seams. good luck. mark knott
> From: Steven Goldate
> Date: 2004/10/19 Tue PM 08:26:03 EDT
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Kiln arch
>
> Hi Folks,
>
> I'm currently building a new 4 port downdraught gas kiln. A friend who is
> quite a knowledgeable kiln builder wants to offset the arch bricks by half a
> brick, so they are staggered and 'interlocked'. He says this will give the
> arch greater strength. However, I'm only familiar with the simpler method of
> just placing them in simple rows. Has anyone got any advice on this?
>
> Thanks,
> Steven
>
> -------------------------------------------------------------------
> Steven Goldate, Editor, Ceramics Today
> http://www.ceramicstoday.com
> Encyclopaedia of Ceramic Artists
> http://ceramicsdictionary.com
> sgoldate@bigpond.net.au; sgoldate@aasb.com.au
> -------------------------------------------------------------------
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
Hank Murrow on tue 19 oct 04
On Oct 19, 2004, at 5:26 PM, Steven Goldate wrote:
> I'm currently building a new 4 port downdraught gas kiln. A friend who
> is
> quite a knowledgeable kiln builder wants to offset the arch bricks by
> half a
> brick, so they are staggered and 'interlocked'. He says this will give
> the
> arch greater strength. However, I'm only familiar with the simpler
> method of
> just placing them in simple rows. Has anyone got any advice on this?
Dear Steven;
Having built both types of arch, I can suggest that the 'bonded' arch
is superior IF the bricks are quite uniform in size. If not, the radial
version is good.
I generally build my arches as a shallow catenary, which uses more
straights and #1s, with #2s in the middle.
Good luck, Hank in Eugene
www.murrow.biz/hank
Craig Edwards on tue 19 oct 04
Steven: He's right. I've never done it other than rowlock fashion. It
will be stronger and airtight.
~Craig
New London, MN
Steven Goldate wrote:
>Hi Folks,
>
>I'm currently building a new 4 port downdraught gas kiln. A friend who is
>quite a knowledgeable kiln builder wants to offset the arch bricks by half a
>brick, so they are staggered and 'interlocked'. He says this will give the
>arch greater strength. However, I'm only familiar with the simpler method of
>just placing them in simple rows. Has anyone got any advice on this?
>
>Thanks,
>Steven
>
>-------------------------------------------------------------------
>Steven Goldate, Editor, Ceramics Today
>http://www.ceramicstoday.com
>Encyclopaedia of Ceramic Artists
>http://ceramicsdictionary.com
>sgoldate@bigpond.net.au; sgoldate@aasb.com.au
>-------------------------------------------------------------------
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
>
>
Richard Aerni on tue 19 oct 04
Steven,
Yes, definitely, you want to stagger the brick. Same as you stagger your
courses in the vertical walls of the kiln. That way if one brick happens
to shift a bit, it won't affect every other brick in that row.
It's not more complicated to build your arch this way (unless you count
cutting a few brick in half as complicated) and you will certainly end up
with a more stable arch.
Good luck,
Richard Aerni
On Wed, 20 Oct 2004 10:26:03 +1000, Steven Goldate
wrote:
>Hi Folks,
>
>I'm currently building a new 4 port downdraught gas kiln. A friend who is
>quite a knowledgeable kiln builder wants to offset the arch bricks by half
a
>brick, so they are staggered and 'interlocked'. He says this will give the
>arch greater strength. However, I'm only familiar with the simpler method
of
>just placing them in simple rows. Has anyone got any advice on this?
Ivor and Olive Lewis on wed 20 oct 04
Dear Steve Goldate,
My experience is that interlocking courses (bonded but not
cemented )in an arch are prone to deterioration as the kiln ages.
Mechanical stress caused by differentially repeated expansion and
contraction can cause some bricks to break into two halves. Heaving
and settling as the kiln heats and cools can allow fragments to drop
into the kiln without the roof collapsing. But it would be unusual for
the whole roof to cave in. If the deterioration is not generalised,
say just a couple of pieces sagging inwards, they can be settled back
into place by striking upwards with a rubber hammer or by placing a
block of wood against and using a lump hammer.
Repairs can be effected by replacing the former under the arch and
releasing the tension on the bearer frame. Broken bricks are then
removed and replaced.
I hope this information assists you.
My only attempt to build a Catenary arch kiln with separate rows was a
disaster. It held up after the form was removed but collapsed in the
gale that sprang up the same night.
I hope you have a great kiln.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Steve Mills on wed 20 oct 04
Steven,
My first (and only) sprung arch fuel kiln was built this way; I got it
second hand and re-assembled it, and despite the bricks being a bit
worn, it held together for ten years without any problems and then did
the same for the Potter who took over that workshop when I moved. For me
that is the only way to do it. If it was a brick wall the way it is laid
would be called a *Stretcher Bond*.
My subsequent fuel kilns have been fibre boxes or (current) top loading.
Steve
Bath
UK
In message , Steven Goldate writes
>Hi Folks,
>
>I'm currently building a new 4 port downdraught gas kiln. A friend who is
>quite a knowledgeable kiln builder wants to offset the arch bricks by half a
>brick, so they are staggered and 'interlocked'. He says this will give the
>arch greater strength. However, I'm only familiar with the simpler method of
>just placing them in simple rows. Has anyone got any advice on this?
>
>Thanks,
>Steven
>
>-------------------------------------------------------------------
>Steven Goldate, Editor, Ceramics Today
>http://www.ceramicstoday.com
>Encyclopaedia of Ceramic Artists
>http://ceramicsdictionary.com
>sgoldate@bigpond.net.au; sgoldate@aasb.com.au
>-------------------------------------------------------------------
--
Steve Mills
Bath
UK
Steven Goldate on wed 20 oct 04
Hi Folks,
I'm currently building a new 4 port downdraught gas kiln. A friend who is
quite a knowledgeable kiln builder wants to offset the arch bricks by half a
brick, so they are staggered and 'interlocked'. He says this will give the
arch greater strength. However, I'm only familiar with the simpler method of
just placing them in simple rows. Has anyone got any advice on this?
Thanks,
Steven
-------------------------------------------------------------------
Steven Goldate, Editor, Ceramics Today
http://www.ceramicstoday.com
Encyclopaedia of Ceramic Artists
http://ceramicsdictionary.com
sgoldate@bigpond.net.au; sgoldate@aasb.com.au
-------------------------------------------------------------------
Earl Brunner on thu 21 oct 04
I think you have already made up your mind. Do it. It's your kiln.
Earl Brunner
Las Vegas, NV
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Steven Goldate
Sent: Thursday, October 21, 2004 4:51 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: kiln arch
I have been told by a college tech person, who is a good kiln builder, that
with the bonded method, the disadvantage is that the bricks tend to crack
though the centre where they meet. He thinks it's not really necessary for a
smaller kiln, that it wouldn't make the arch stronger. My arch will be 13
bricks across. He says the theory is if one brick falls out, the rest of
the ring doesn't fall, but he's never seen that happen. Mt arch bricks are
also cut to a wedge, so it's not really possible for one to 'fall'.
What do you think?
Thanks again,
Steven
-------------------------------------------------------------------
Steven Goldate, Editor, Ceramics Today
http://www.ceramicstoday.com
Encyclopaedia of Ceramic Artists
http://ceramicsdictionary.com
sgoldate@bigpond.net.au; sgoldate@aasb.com.au
-------------------------------------------------------------------
____________________________________________________________________________
__
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
shane mickey on thu 21 oct 04
just as a note/ reminder, when laying arch on arch form, be sure that the upper brick's lower edge is just slightly set back from the one below, this helps to prevent the bricks from slipping out of the arch, especially the straights. This is easily overlooked once the form is in place and we get excited to lay that arch! An arch should be approached and laid very methodically.
shane mickey
_______________________________________________
Join Excite! - http://www.excite.com
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John Britt on thu 21 oct 04
Steve,
I would agree with him on that size kiln. It will work fine.
Love your site, www.ceramicstoday.com, too!
John Britt
www.johnbrittpottery.com
Edouard Bastarache Inc. on fri 22 oct 04
Hello Vince,
how about putting a blanket of man-made insulating fibers instead of the
castable stuff?
Later,
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
Steven Goldate on fri 22 oct 04
I have been told by a college tech person, who is a good kiln builder, that
with the bonded method, the disadvantage is that the bricks tend to crack
though the centre where they meet. He thinks it's not really necessary for a
smaller kiln, that it wouldn't make the arch stronger. My arch will be 13
bricks across. He says the theory is if one brick falls out, the rest of
the ring doesn't fall, but he's never seen that happen. Mt arch bricks are
also cut to a wedge, so it's not really possible for one to 'fall'.
What do you think?
Thanks again,
Steven
-------------------------------------------------------------------
Steven Goldate, Editor, Ceramics Today
http://www.ceramicstoday.com
Encyclopaedia of Ceramic Artists
http://ceramicsdictionary.com
sgoldate@bigpond.net.au; sgoldate@aasb.com.au
-------------------------------------------------------------------
Vince Pitelka on fri 22 oct 04
>I have been told by a college tech person, who is a good kiln builder, that
> with the bonded method, the disadvantage is that the bricks tend to crack
> though the centre where they meet. He thinks it's not really necessary for
> a
> smaller kiln, that it wouldn't make the arch stronger. My arch will be 13
> bricks across. He says the theory is if one brick falls out, the rest of
> the ring doesn't fall, but he's never seen that happen. Mt arch bricks are
> also cut to a wedge, so it's not really possible for one to 'fall'.
Steven -
Pardon my directness, but your tech is mistaken. The locked arch is always
better for studio kilns, and if properly laid, the bricks will not crack
through the center where they meet. In all truth, I must ask "Where the
hell did he get that idea?" I have never heard of that happening in a
well-built kiln arch.
Here's a major tip, though. With most sprung arches, we generally add an
insulating layer of castable refractory over the 4 1/2" brick arch. Always
put down a layer of plastic wrap or aluminum foil over the brick arch before
adding the castable layer. You do NOT want the brick arch bonded to the
castable layer. They need ot expand and contract independently. I think
that a lot of the problems with bricks slipping out of sprung arches have to
do with bonding to the insulating layer. It creates voids and slop in the
arch, whereas if the two layers can expand and contract independently, they
both remain tight, and there will not be such problems.
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Gary Navarre on sat 23 oct 04
---------------------------- Original Message ----------------------------
Subject: Re: kiln arch
From: "Vince Pitelka"
Date: Sat, October 23, 2004 7:14 pm
To: CLAYART@LSV.CERAMICS.ORG
--------------------------------------------------------------------------
> how about putting a blanket of man-made insulating fibers instead of the
castable stuff?
Edouard -
That works great from an insulating point of view, but I like more
rigidity - the castable insulating layer accomplishes that. I just use a
homemade castable mix - by volume, one part portland cement to two parts
fireclay to three parts cheap sand to four parts sawdust. I mix it thick
in a big tub, and pat it in place. It cracks when it shrinks upon drying,
and I just add more of the same to patch up the cracks. It smokes a lot
during the first few firings, as the sawdust burns out, but that leaves
insulating voids.
- Vince
Hay Guys,
I did something similar, Vince, on the last kiln. I put a layer of 1/2"
blanket on the hard brick and covered with the mix minus the cement. I
think I covered that again with firebrick layed on their edges. Too bad
I don't have a negative scanner or I could post shots of that old kiln.
Still I had to cover with insulators but when I did there was no heat
loss. I'm thinking red brick would do the same. Since I have it to do
over I would cover with the mix first, then the blanket, then the
insulators. When I dismantled the blanket was crushed some lessening its
air spaces. I was able to save some of it but don't recall what it looks
like now.
Am I to understand the Portland has some refractory properyes or is it
used only as a binder?
G. in Da U.P.
Navarre Pottery
Norway, Michigan, USA
Vince Pitelka on sat 23 oct 04
> how about putting a blanket of man-made insulating fibers instead of the
> castable stuff?
Edouard -
That works great from an insulating point of view, but I like more
rigidity - the castable insulating layer accomplishes that. I just use a
homemade castable mix - by volume, one part portland cement to two parts
fireclay to three parts cheap sand to four parts sawdust. I mix it thick in
a big tub, and pat it in place. It cracks when it shrinks upon drying, and
I just add more of the same to patch up the cracks. It smokes a lot during
the first few firings, as the sawdust burns out, but that leaves insulating
voids.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
John Britt on sat 23 oct 04
Vince,
You wrote:
"Pardon my directness, but your tech is mistaken. The locked arch is
always
better for studio kilns, and if properly laid, the bricks will not crack
through the center where they meet. In all truth, I must ask "Where the
hell did he get that idea?" I have never heard of that happening in a
well-built kiln arch."
Very few things are "always" the case and this is one of them. For
example: there are three kilns that are in use at Penland with ring
archs. One is ten years old and counting. Looks like it is headed for at
leat 20 yrs. Another is a salt kiln that has 5 plus years in. (Probably
fired 10 - 15 times a year) It has been through an explostion and other
assorted vary bad things. It still is working. The base is the problem
not the arch. And another test kiln that I built which has been in heavy
use for 3 years. It is often fired daily! Still looking good.
So I have to disagree with you that ring arches are sometimes good, as are
interlocking arches. It depends on the situation.
John Britt
www.johnbrittpottery.com
Louis Katz on sat 23 oct 04
If the metal holding the skews warps, or the kiln becomes unsquare
somehow the bricks crack. If the bricks are not all the same size as in
hand made arch brick cut from straights, they snap.
On Oct 22, 2004, at 7:19 PM, Vince Pitelka wrote:
>> I have been told by a college tech person, who is a good kiln
>> builder, that
>> with the bonded method, the disadvantage is that the bricks tend to
>> crack
>> though the centre where they meet. He thinks it's not really
>> necessary for
>> a
>> smaller kiln, that it wouldn't make the arch stronger. My arch will
>> be 13
>> bricks across. He says the theory is if one brick falls out, the
>> rest of
>> the ring doesn't fall, but he's never seen that happen. Mt arch
>> bricks are
>> also cut to a wedge, so it's not really possible for one to 'fall'.
>
> Steven -
> Pardon my directness, but your tech is mistaken. The locked arch is
> always
> better for studio kilns, and if properly laid, the bricks will not
> crack
> through the center where they meet.
FRom another post
> "Be careful
> of words like "always."
> - Vince"
Sorry I told myself I would lighten up.
Louis
Louis Katz on sun 24 oct 04
Hi Vince,
I have never had bricks in the arch crack on my kilns that I know of,
never had an arch fall, have never seen one fall except where the metal
holding the kiln together failed. But I have seen loose brick, I have
seen cracked brick, I have seen arches so close to falling that they
were replaced, I have seen arches bonded and not loose portions of
brick as they age Then again I have seen little chunks fall.
I have built kilns of materials that I had on hand when there was no
money to buy more. Maybe you have different kinds of budgets where you
teach. When the money is there I do things first class, when it is not,
I do what I can and try not to chase cows rather than fixing the fence.
Unfortunately I do occasionally chase cows. I try to have fun doing it.
I work at a school that has had essentially a flat budget for the last
few years and has doubled in enrollment in the last 8 or so years. We
are not long on cash. I have had softbrick donated, I inherited some
hard brick. Only a few arch brick in the lot.
Although it is work, I enjoy making the jig for cutting arch brick.
When I do it myself they come out flat and true. When students help
some come out uneven. I let them help. I use the brick. I would think
hard before using them in a bonded arch. Rings work fine so long as
they are carefully laid. There is not any more or less straight though
places than there is in a bonded arch. I am making the point that there
are circumstances when one should not use a bonded arch. I have built
both ways.
I could see myself castigating someone for saying always in
questionable circumstances and then in the same day doing it myself."
Never say never" is such a telling phrase I think it is so human and
tells so much about the trap of language , "never say always" has no
such obvious irony, but it is still there.
Louis Katz
http://www.tamucc.edu/~lkatz
Edouard Bastarache Inc. on sun 24 oct 04
Hello Gary,
what I actually did was to put a high quality asbestos blanket
right over the arch to seal it, overlapping 4 feet (not foots,hehehe),
then i covered everything with a Kaowool blanket.
When I do not fire I put overlapping plastic carbage bags (clean
of course) to keep the fibres down and protect the arch against water
if the roof decides to leak, it has happened a few times.
Later,
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
Vince Pitelka on sun 24 oct 04
> If the metal holding the skews warps, or the kiln becomes unsquare
> somehow the bricks crack. If the bricks are not all the same size as in
> hand made arch brick cut from straights, they snap.
Louis -
That tells us several things. First, always build your kiln frame sturdy
enough that it won't warp, and second, use commercially made arch bricks.
It surprises me that anyone would make their own arch bricks from straights
just to save a few bucks. I have never done that, and I have always built a
very sturdy kiln frame, so I have not had this problem with bricks snapping
in half.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Vince Pitelka on sun 24 oct 04
> Am I to understand the Portland has some refractory properyes or is it
> used only as a binder?
Gary -
The Portland cement does not have any refractory properties, and in fact
excessive Portland cement on the hotface will create a castable that melts
and slumps beautifully. I would avoid using any Portland cement on a
high-temperature hotface. But on an exterior layer it reduces shrinkage
cracks and increases durability and weather-resistance.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
shane mickey on mon 25 oct 04
hey group,
wow the bonded non-bonded arch is a hot topic,
always the devils advocate: john, i can confirm that the ring arches at penland are holding quite well, but i think the real problem with a ring arch is when the rings start to seperate ever so slightly, this causes two problems, one (in the case of atmospheric kilns) it allows the corrosive agents farther into the brick work thus compromising the kiln brick more than usual. two when they seperate you face a loss of heat, and since the arch is the highest point, i think that is significant, fiber, second course of brick, etc. all will aid, but still, heatloss occurs. I have noticed that most ring arches do seperate overtime. as for bonded arch, i have seen many of these with broken bricks, i have always understood that this is due to the kiln walls being unlevel, unplumb, unsquare or a combo of all the above. once these crack then you have a compromise in the arch also. As a side note i have seen kilns built to within a 32nd of an inch and as plumb and square as can be, I have also
seen the opposite, and i have seen both types last for many years and both fail miserable. One of the main factors for a kilns longevity is how it is kept up. this is one of the reasons penlands kilns
last so long, they are very well maintained!
shane mickey
_______________________________________________
Join Excite! - http://www.excite.com
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Dennis Tobin on mon 25 oct 04
Gary and Vince,
I have actually used Portland cement as a high fire glaze on the
outside of pots. It looks a bit like and ash glaze.
Dennis Tobin
On Oct 24, 2004, at 7:34 PM, Vince Pitelka wrote:
>> Am I to understand the Portland has some refractory properyes or is
>> it
>> used only as a binder?
>
> Gary -
> The Portland cement does not have any refractory properties, and in
> fact
> excessive Portland cement on the hotface will create a castable that
> melts
> and slumps beautifully. I would avoid using any Portland cement on a
> high-temperature hotface. But on an exterior layer it reduces
> shrinkage
> cracks and increases durability and weather-resistance.
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft, Tennessee Technological University
> Smithville TN 37166, 615/597-6801 x111
> vpitelka@dtccom.net, wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka/
> http://www.tntech.edu/craftcenter/
>
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