mark knott on mon 9 feb 04
I am in the process of finally building my kiln. it is only about a year =
later than originally planned. oh well. the question I have, what are =
opinions of fellow clayart kiln builders on expansion joints? the =
planned kiln is 63 x 31.5 x 45.5 to the top of the arch. this kiln will =
be built out of hard brick and backed by soft brick. crossdraft and =
fired with ward power burners. I've read many varying opinions on the =
use of expansion joints. are the really critical? do they go in every =
row? should they be staggered? and lastly should both the inside and =
outside wall have these joints? I'm guessing the joints, if needed =
,would not line up the entire length of the wall. and how do you figure =
the expansion joint into the header course. any input or advise would be =
greatly appreciated. thanks, mark knott
Richard Aerni on mon 9 feb 04
Hello Mark,
I'm also building a kiln at the moment. I may be a bit further along than
you, as the brick and angle iron is already laid up and now it's time for
the arch. Here's what I did, and how it has worked on previous kilns I've
built (and I'm sure you'll get plenty of other opinions, pro and con,
probably all of which worked fine for the kiln in question).
Mine, like yours, has a hard brick interior with a soft brick exterior.
I've incorporated room for about 1/4 inch of expansion per course in my
interior (hard brick) walls. Much of this is left at the end of the
course, but I've made it a point not to butt each brick up to the other so
tightly that a piece of paper couldn't get through the joint. I figure
that the movement is likely to take place throughout the entire course of
brick, so didn't want to have just one space at the end. Plus I figure
that I've staggered the joints from the interior to the exterior course, so
nowhere does the interior joint pass through to the outside of the kiln
without being covered by the soft brick outer course. I did not leave much
room for expansion in my outer soft brick wall, because the brick, if it
moves, will be able to crush itself against the angle iron without
deforming the walls, like would happen with inflexible hard brick. I've
never had a problem with the softbrick outer wall moving in any of my other
kilns.
My kiln walls are 60 1/2 inches high, and I don't have a soldier course in
them. For the area around the burner ports (which enter from the side),
there are soldier bricks, but no soldier course. Likewise, in the rest of
the walls, I've got two courses where there are the odd soldier bricks, but
have never found the need for an entire soldier course. The occasional
soldier "tie" brick seems to keep the walls together just fine.
So, hope this has given you at least another opinion. I don't know the
details of your construction, nor you mine, so we may be talking at cross
purposes. But, it's probably a good rule of thumb to overbuild, not
underbuild, when putting your kiln together.
Good luck,
Richard Aerni
On Mon, 9 Feb 2004 18:49:07 -0800, mark knott wrote:
>I am in the process of finally building my kiln. it the question I have,
what are opinions of fellow clayart kiln builders on expansion joints? the
planned kiln is 63 x 31.5 x 45.5 to the top of the arch. this kiln will be
built out of hard brick and backed by soft brick. crossdraft and fired with
ward power burners. I've read many varying opinions on the use of expansion
joints. are the really critical? do they go in every row? should they be
staggered? and lastly should both the inside and outside wall have these
joints? I'm guessing the joints, if needed ,would not line up the entire
length of the wall. and how do you figure the expansion joint into the
header course. any input or advise would be greatly appreciated. thanks,
mark knott
Vince Pitelka on mon 9 feb 04
> that I've staggered the joints from the interior to the exterior course,
so
> nowhere does the interior joint pass through to the outside of the kiln
> without being covered by the soft brick outer course.
Richard -
I am a little confused by this. If you don't have any joints passing
through the walls, how did you accomplish your header courses, which tie the
inside and outside layers together? With each header courses, the joints do
pass through the entire thickness of the wall, bu the header courses are
absolutely necessary for a stable, locked wall.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Office - wpitelka@tntech.edu
615/597-6801 x111, FAX 615/597-6803
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Vince Pitelka on tue 10 feb 04
Mark -
Great to hear that you are building your soda kiln. Normally there is no
need to put any expansion joints in soft brick, but you should leave a
little expansion space in the hardbrick, and thus you will have to do it to
the softbrick as well. For each dimension on the kiln (the two side walls
and the back wall), I would leave a total of about 1/4" of expansion space.
So just leave a very small space between each brick in the stretcher
courses - a shim like a piece of posterboard might help, but it really
isn't critical. When you lay the header courses, just use a piece of paper.
Yes, that does leave a minute gap leading to the outside of the kiln, but
after the first few firings everything will have stabilized in terms of
where the expansion and contraction takes place, and then you can mix a
mortar of fireclay and vermiculite and seal any gaps showing on the outside
of the kiln.
Have someone take a very bright light - like a halogen worklight, and shine
it towards the wall on the inside, while you examine the corresponding part
of the wall on the outside. Do that over all the inside walls of the kiln.
It is a simple matter to seal up the gaps.
You should repeat that every few years, because inevitably, tiny gaps will
open up again. Some people just don't worry about them, but I like a tight
kiln, where all atmospheric transfer is taking place at the burner ports,
the flue, and the spy ports.
Good luck -
- Vince
Vince Pitelka
Associate Professor of Clay
Head, Clay Area
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive
Smithville, TN 37166
931/372-3051 x111
or 615/597-6801 x 111
Fax 615/597-6803
wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Vince Pitelka on wed 11 feb 04
> brick chimney is a bit loose. I can see the flames through the
> cracks during the firing. I'm sure these cracks must be functioning
> like a passive damper, but I wonder if I should worry about it. And if
> I do decide to seal the cracks up, would your suggested mortar of
> vermiculite and fireclay be a good material? Or perhaps some other
> blend. I was thinking of perhaps a blend of cement and clay.
John -
Yes, I think you should seal up the holes, in order to maximize the
available stack draft that you can regulate with the damper. For this
application, I think your idea is better, but use a mix of about 50% sand or
grog, 40% fireclay or stoneware clay, and 10% portland cement.
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Office - wpitelka@tntech.edu
615/597-6801 x111, FAX 615/597-6803
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
John Jensen on wed 11 feb 04
Vince;
Your advice to Mark brings up a question I have about my own little gas
kiln...perhaps you'd be kind enough to offer a point of view.
The kiln fires quickly to cone 10 and beyond and is quite tight, but
my brick chimney is a bit loose. I can see the flames through the
cracks during the firing. I'm sure these cracks must be functioning
like a passive damper, but I wonder if I should worry about it. And if
I do decide to seal the cracks up, would your suggested mortar of
vermiculite and fireclay be a good material? Or perhaps some other
blend. I was thinking of perhaps a blend of cement and clay.
John Jensen, Mudbug Pottery
mudbug@toadhouse.com , http://www.toadhouse.com
pdp1@EARTHLINK.NET on wed 11 feb 04
Why not just caulk the chinks with Kaowool?
Phil
Las Vegas
kterpstra on thu 12 feb 04
Hi Mark,
I put an expansion joint in each chamber on the floor of my kiln. I
wanted to cover all the bases when we built our "over-built" kiln. (I
call it the Hum-vee now.) Floors can move around too and are a pain in
the *%#* to fix. In both chambers we put them one brick length back
from the bag walls. I filled them in with Ka-wool. I can still post
over it in the first chamber and we side stoke next to it in the back
chamber. I can tell we've had a bit of movement and settling after 3
years. I'm glad they are there. Vince has good advice about the
walls.we did the same thing. Contact me if you have any further
questions about it.
Karen Terpstra
La Crosse, WI
http://www.uwlax.edu/faculty/terpstra/
http://www.terpstra-lou.com
Vince Pitelka on thu 12 feb 04
> Why not just caulk the chinks with Kaowool?
Because no one should be messing with loose Kaowool any more than absolutely
necessary, because it is so severely carcinogenic.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Office - wpitelka@tntech.edu
615/597-6801 x111, FAX 615/597-6803
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
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