jims@connect.ab.ca on mon 15 apr 96
Hi Folks,
It's time for my annual "gotta do something with my arch and kiln door"
again. *8)
For the last several years I've been threatening to cast an arch (to
replace the existing brick one) and possibly some blocks for the door -
instead of re-doing everything in 2600's.
I recall reading an article (from about 12 - 15 years ago) on someone
testing "several" castable compositions - then constructing a series of
kilns which were repeatedly fired to ^10 with fairly good results. They
also gave comments on each castable as to the refractory qualities they
observed.
Can't seem to find the article anywhere - in any of my books or magazines
from around that vintage... I have a feeling it was originally in a
Ceramics Monthly but could be wrong on that. (maybe this means I'd better
get after that spring cleaning so I can find things again)
If anyone recalls such an article and have an issue #/date (if is was a
magazine), could you please let me know what it is... it would be much
appreciated.
Also, if anyone has had experience in making their own castables for such
a purpose... I'm also open to suggestions.
eg.- How good would castable really be for a sprung arch with about a 10"
rise over a 4' span (haven't done the final rise calculations yet). Or is
it asking too much of that medium? I've only seen castable used on top of a
layer of brick when the rise was that low. Any of the "stand alone"
castables were either more of a barrel vault or (in most situations) a
catenary arch.
...hmmm, maybe I should be considering ceramic fibre... *8)
Cheers... Jim
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
jims@connect.ab.ca Edmonton/Alberta/Canada
http://www.connect.ab.ca/~jims/
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Marvin Bartel on mon 15 apr 96
>from:
jims@connect.ab.ca Edmonton/Alberta/Canada
>Hi Folks,
> For the last several years I've been threatening to cast an arch (to
>replace the existing brick one) and possibly some blocks for the door -
>instead of re-doing everything in 2600's.
In the 1970's we used a homemade castable developed by potter by
the name of Leach in Albion, Michigan. Heis no longer living. Here is the
batch used. Do not wiegh the ingredients. Use a scoop or can to measure
by volume.
Sawdust (granular, not fine) --------- 1.5
Vermiculite (as used in potting soil) 1.0
Fire Clay (A.P. Green) ------------------ 2.0
Portland Cement ------------------------- 1.0
Alumina ----------------------------------- 0.5
Water -------------------------------------- 1.5
This material is mixed dry first. Add only enough water to make it clump
when packed. We packed it in the forms using the end of a 2x4 tamper.
Mixing it quite dry reduces shrinkage.
We made a 2 chamber catenary soda vapor kiln with cast walls 4
inches thick. Expansion joints are left by placing paper in the castable
after forming a compound notch in the tamped material. The joints are
about every 18 inches or so. Door chuncks are done the same way. We fired
to cone 8 to 10 with gas.
CAUTION: Ours gave way after about 30 firings because we added 1
inch of mineral block insulation on the outside for fuel saving. This
caused the area between the two arches to begin to melt.
The portland cement makes it quite weather resistant, but it also
lowers the temp. Calcium Aluminate cement is made by LA FARGE CORP
someplace in NW Ohio. I can't vouch for the strength, but it has a higher
melting temperature. Kyanite is fairly inexpensive material high in
alumina. Adding some kyanite might help. It comes from Virginia Kyanite.
Hope this helps.
LOWELL BAKER on mon 15 apr 96
I am probably the one who write the article on castables. It was
published in 1981 or 1982 in CM. I have not used these castables on
a sprung arch, but I can't see why a good dense castable would not
hold up to the job. In the frozen north you must watch free=zing and
thawing even more than bricks. Look at the articles and then call or
E-mail me for more direct info.
Lowell
The University of Alabama
art_selsor@vicuna.emcmt.edu on tue 16 apr 96
Dear Lowell,
I used such a castable when I built a soda kiln in Rock Springs Wyo.
From what I gather, it still works fine after 11 years. I was just about
to start on one at our campus in Billings (a few thousand feet below
Rock Springs alt.) I have built catenary arches with these castables.
I helped to build a sprung arch from one in Phila. at the U of Arts.
It worked fine. Must provide tension supports i.e. angle iron braces
across the top. I prefer hinged doors as well. SAVE MY WRISTS (SMW)!
Thanks for your formula. I think it is a great way to build a simple kiln
with students. I was thinking of added insulation, thanks for the tidbit
re: portland cement melting. Plan to cast arch in a week or so. ERnjoying
the thaw in Montana. Marcia http://www.imt.net/~mjbmls/HomePage.html
jims@connect.ab.ca on wed 17 apr 96
Hi Folks,
Thanks very much for the *several* quick responses...
>I am probably the one who write the article on castables. It was
>published in 1981 or 1982 in CM. I have not used these castables on
>a sprung arch, but I can't see why a good dense castable would not
>hold up to the job. In the frozen north you must watch free=zing and
>thawing even more than bricks. Look at the articles and then call or
>E-mail me for more direct info.
>Lowell
>The University of Alabama
Marv <@AOL> did a check on the CMindex program for me and came up with the
article(s) I was thinking of - from the Nov./81' Ceramics Monthly.
Lowell, I'm now quite sure your article is indeed one of the two in that
issue I was after... just have to get my hands on a copy if I can't find the
one I had.
As for the "frozen north"... hey, it's the only place you can freeze-dry
your pots and have that freshness locked in. (sorry, couldn't
resist) *8)
You're likely right about freezing being a potential problem for the
castable - especially on an unsupported low rise cast arch that's exposed to
the weather. Most damage would probably occur when going through one of the
many freeze/thaw cycles (occasionally supplied by the kiln itself). My
present arch is a soft-brick layer with a 5" layer of a
bentonite/vermiculite mix on top. Over that is a thin sheet of aluminum
flashing to protect the "mix" layer from rain/snow, etc. That seems to have
worked quite well for about 14 years. The more I think about this project,
the more I think I might just end up repeating that arch - this time using
the castable instead of the vermiculite mix and still go with a brick layer.
The door could also be cast at the same time - or once tests are done to
find out the shrinkage from the "first cast" to the "fired" state.
Thanks again people, much appreciated!
Cheers... Jim
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
jims@connect.ab.ca Edmonton/Alberta/Canada
http://www.connect.ab.ca/~jims/
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