Brad Sondahl on wed 29 sep 99
Still firing the original Crusader kiln I bought used 25 years ago, I'm
wondering if anyone has ever experienced a major electric kiln lid
failure. This includes the floor, which is the same idea: a stainless
steel band holding a rounded lot of insulating brick together. I've
actually replaced the top lid several times, usually when bits crumble
off spoiling the glazed work on the top shelf.
I've also had to replace sheetmetal screws on the handle or on the hose
clamp pieces that tighten the band around the lid. With time and lots of
firing, these sheet metal screws slowly corrode until they resemble
nails more than screws. If the hoseclamps were to pull loose during a
firing, it seems catastrophic failure could occur.
Actually the bottom lid seems much more prone to failure, as it sits on
a small metal base, has to support the weight of the kiln, and usually
(on three to 6 posts), the weight of all the pottery in the kiln. In
addition to all this, I like to leave an aluminum pan of trimmings on
top of the kiln to dry them for recycling. This represents an
additional 20 lbs or so of stress.
At the camp I was just at, someone had taken an old electric kiln
outside to use for raku. They had drilled a 4 inch hole in the top, and
left it out over the winter where they got over 10 feet of snow last
winter. This lid had collapsed, but given the conditions I don't blame
it.
So has anyone ever had one collapse?
--
Brad Sondahl
http://www.camasnet.com/~asondahl/bradindex.html
Sondahl homepage http://www.camasnet.com/~asondahl
Original literature, music, pottery, and art
zahidi neale on thu 30 sep 99
The top on one of my little old Paragons is repaired around the hinge, but
still holding. (Knock wood, and I'm REALLY careful with the lids.) It has a
6 year old bottom, though. Replaced it after one moving fiasco. I had had
the middle of the metal bottom cover rust out of the old dog after only 25
years! So I went to a sheet metal place (A/C, etc) and they cut me a scrap
to fit exactly on the top of my stand, which is the standard Paragon angle
iron/ open in the center/ square setup. The sheet metal is pretty thick and
seems to do the trick. I didn't have to order a new bottom cover or go to
the hassle of taking it apart again. They gave it to me free, but I gave
them a planter anyway. When I buy a new kiln now, I will do this immediately
to protect the new bottom. I don't think it affects heat dispersion anyway,
as there are no elements in the bottom of this kiln. Could be different with
bottom venting systems, etc.
By the way, Euclid elements are WAY superior to the Paragon manufacturer's.
Zee in Slidell, LA where the bayou water is finally rising.
-----Original Message-----
From: Brad Sondahl
To: CLAYART@LSV.UKY.EDU
Date: Wednesday, September 29, 1999 9:35 AM
Subject: Electric kiln lid/bottom failures?
>----------------------------Original message----------------------------
>Still firing the original Crusader kiln I bought used 25 years ago, I'm
>wondering if anyone has ever experienced a major electric kiln lid
>failure. This includes the floor, which is the same idea: a stainless
>steel band holding a rounded lot of insulating brick together. I've
>actually replaced the top lid several times, usually when bits crumble
>off spoiling the glazed work on the top shelf.
>I've also had to replace sheetmetal screws on the handle or on the hose
>clamp pieces that tighten the band around the lid. With time and lots of
>firing, these sheet metal screws slowly corrode until they resemble
>nails more than screws. If the hoseclamps were to pull loose during a
>firing, it seems catastrophic failure could occur.
>Actually the bottom lid seems much more prone to failure, as it sits on
>a small metal base, has to support the weight of the kiln, and usually
>(on three to 6 posts), the weight of all the pottery in the kiln. In
>addition to all this, I like to leave an aluminum pan of trimmings on
>top of the kiln to dry them for recycling. This represents an
>additional 20 lbs or so of stress.
>At the camp I was just at, someone had taken an old electric kiln
>outside to use for raku. They had drilled a 4 inch hole in the top, and
>left it out over the winter where they got over 10 feet of snow last
>winter. This lid had collapsed, but given the conditions I don't blame
>it.
>So has anyone ever had one collapse?
>--
>Brad Sondahl
>http://www.camasnet.com/~asondahl/bradindex.html
>Sondahl homepage http://www.camasnet.com/~asondahl
>Original literature, music, pottery, and art
Candise Flippin on thu 30 sep 99
Brad,
I bought my Crusader used in 1986 and likewise is just keeps on
ticking. I keep expecting it to just die one day, but my kiln log still
show very consistent firings. I have had the same fears of lid and
floor failure even to the point that I really do not know how it has
stayed together. It has also been moved several times. A few years ago
I bought a new lid from AMACO, replaced the floor with the old lid, and
installed an Envirovent. I am more comfortable that the floor has
better support, but the other problems you mentioned still continue. I
will also be very interested in any other comments aout these issues
that are share with the list.
Thanks, Candise (in Santa Ana windy San Diego)
Carolynn Palmer on thu 30 sep 99
I have 7 old Crusaders, 4 of which I fire almost daily and I am constantly
replacing kiln lids - at least two per year. I fire with a double lid on the
top of these every time and once, the stainless steel band gave way and the
inner lid crumbled apart in the center and fell into the kiln. Its edge
brick were held onto the kiln by the second lid, though, so there was no
heat-type disaster. What a mess inside, however.
My original Crusader came from Thermatron Corporation near Holland, Michigan
about 30 years ago. Right now I have one whose jacket is being held on by
only two hose clamps. These clamps also disentegrate over time. They are
only pop riveted onto the jacket and the rivets disappear over time. Guess I
will be replacing the hose clamps soon. Also, I have one whose stainless
steel jacket is so thin and worn that I cannot find a good enough spot on it
to screw or rivet anything to - long ago lost its handles, etc.
In these kilns defense, I must say that I have rebuilt them from the elements
to the jacket (haven't replaced a jacket, yet) when they start to wear, and
they just go on firing.
Carolynn Palmer, Somerset Center, Michigan
Vince Pitelka on fri 1 oct 99
>Actually the bottom lid seems much more prone to failure, as it sits on
>a small metal base, has to support the weight of the kiln, and usually
>(on three to 6 posts), the weight of all the pottery in the kiln. In
>addition to all this, I like to leave an aluminum pan of trimmings on
>top of the kiln to dry them for recycling. This represents an
>additional 20 lbs or so of stress.
>So has anyone ever had one collapse?
Brad -
I have never seen the lid of a toploader kiln actually collapse. If a lid
had been dropped shut several times and was badly cracked, and then if the
band clamp failed, I suppose it would be possible for it to collapse during
a firing. But if the refractory is in sound shape, even if the band clamp
failed I cannot imagine it collapsing.
The bottom is prone to failure only if the kiln is stacked improperly. This
is why I dislike one-piece kiln shelves in toploader kilns, except for very
small ones. With a one-piece shelf, supported in three places, it is
impossible to transfer the full weight of the set down to the steel frame
beneath the floor. In contrast, when using two half-shelves supported by
four posts in each layer, it is possible to place the posts directly above
the steel frame. If this is done religiously, and barring other
catastrophic damage, the kiln floor should last almost indefinitely.
Personally, I am very careful not to ever load the lid of a toploader kiln
with any appreciable weight. It is just inviting damage.
Best wishes -
- Vince
Vince Pitelka
Home - vpitelka@DeKalb.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
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