Linda Ziesmer on thu 3 apr 03
I'm finally getting ready to order my first kiln (yea!) and would appreciate
any feedback about the pros and cons of ordering the optional powered
bottom. I'm looking at the L&L J2927 with 3" walls. It is 10.17 cu. ft. I
essentially intend to fire bisque and glaze to cone 6. The L&L FAQs state,
"We recommend this option for a few different reasons: 1) If you are firing
very dense loads such as tiles. 2) On very large kilns such as the T3400
Series, where you could get a cold spot in the floor, a powered bottom will
improve uniformity. 3) To decrease cycle time and add KW to the kiln - not
normally an issue with ceramics but it can be for some industrial processes.
4) To increase the temperature rating of a J23 or J2918 kiln. 5) Another
benefit of a powered bottom is that it increases the element life by
allowing all the elements to work less hard to achieve the same results.
I'm not planning on firing tile or especially dense loads (although I've
learned never to say never) and reasons 2-4 don't seem to apply, so is added
element life enough of a benefit to justify the added expense up front as
well as the ongoing operating costs? Are there other reasons to consider a
powered bottom?
Thanks for helping me sort this through,
Linda
lziesmer@umich.edu
Roger Korn on thu 3 apr 03
I try to avoid designing elements into the floor, for the reasons Arnold
mentions. However, when a kiln gets above about 36" in diameter, the
difference in heat transfer by radiation between pots in the center of
the stacking and those closer to the elements limits the acceptable rate
of temperature rise. Adding elements in the floor helps with this
problem, but keeping the kiln floor clean after each firing becomes
important, or element life will be limited by contamination. Coating the
elements with ITC 213 should help eliminate this problem. I'm building a
40 cu ft kiln with elements in the floor and in the door. This kiln is
36 x 36 x 54 interior dimensions and will require about 80 amps of 240
volt power. The heating is divided into 4 zones: the floor, and three
horizontal zones that will require that the door elements be divided
into three sections, with a lot of wiring in the hinge, thus requiring
careful design.
Designed specially for firing large sculpture pieces, the controller
will allow drying ramps from 100F to 200F that will last several weeks
before continuing. Really a fun project!
Roger
Arnold Howard wrote:
>I'm curious to know what everyone thinks of the element in the kiln
>bottom. Paragon does not offer that as a standard feature, because kiln
>wash falling onto the kiln bottom can ruin the element. Also, the
>element limits where you can place the posts on the floor of the kiln.
>
>Sincerely,
>
>Arnold Howard
>Paragon Industries, L.P.
>www.paragonweb.com
>
>
>
>
--
Roger Korn
McKay Creek Ceramics
In AZ: PO Box 463
4215 Culpepper Ranch Rd
Rimrock, AZ 86335
928-567-5699 <-
In OR: PO Box 436
31330 NW Pacific Ave.
North Plains, OR 97133
503-647-5464
william schran on thu 3 apr 03
Arnold asked about element in the bottom and possible problems with
kiln wash flaking into them and limitations on kiln post placement.
Arnold - I don't think a floor element is necessary in kilns up to
about 7 cu. ft., larger kilns I think do benefit from a element in
the bottom. I have a L&L 2900 series (2 1/2" walls) that I wish had a
floor element. Also have a Axner super kiln, their largest (made by
Olympic), that has a floor element. I think I'd have tough time
reaching cone 6 in a reasonable amount of time without the floor
element. Both kilns only use have shelves. One does have to be
careful about the flaking kiln wash - I use a vacuum if anything
drops to the bottom. There is enough floor space around the element
that allows me to place the kiln posts in any position.
Bill
Jim Brooks on thu 3 apr 03
I have used both types of kilns --with and without the element in the bottom
of the kiln. I know that paragon states that you can stack greenware on
the floor and place the shelf supports on the floor of the kiln. In
practice, however, you may/can cause damage to the bottom of the kiln
floor.. post -- when loaded heavily -- will/can damage the fire brick. If
it is a glaze firing and any glaze pops off --or runs-- then you have some
big time damage to the fire brick..
Most of the potters I know, and have known , place a whole or two half
shelves in the bottom of the kilns to stack on..These shelves are placed on
shelf supports -- with the supports laying down so that the sides of the post
support the shelves. This provides a broader area to support the shelf and
spreads the load over a larger area of the floor. These shelf supports
(posts) can be placed in between the elements in the floor and do not
present a problem.. This also keeps kiln wash, glaze, broken pots, etc. from
flaking into the element grooves and damaging the elements.
I use Paragon kilns.. four at home and four at school.. BUT-- I do like the
elements in the floors..even under the bottom kiln shelves-- it seems to
provide a more even heating.. (I have used witness cones /cone-paks to test
this ..) Also, I often "Candle" the kiln overnight with one element on low
-- lid cracked a little... (often do this at school due to the variation in
thickness and dryness of the clay). If the floor element is on a separate
switch it makes a great heat source for the single element candle
procedure..
In truth, I wouldn't reject a kiln on this basis alone.. but it would be
nice to have.
Jim
in Dentonl
Cindi Anderson on thu 3 apr 03
But doesn't everyone use a shelf at the bottom of the kiln to protect the
bricks anyway? Except maybe the rare case of bisque'ing an item that barely
fits inside the kiln where I might go without the bottom shelf.
Cindi
----- Original Message -----
From: "Arnold Howard"
> I'm curious to know what everyone thinks of the element in the kiln
> bottom. Paragon does not offer that as a standard feature, because kiln
> wash falling onto the kiln bottom can ruin the element. Also, the
> element limits where you can place the posts on the floor of the kiln.
Arnold Howard on thu 3 apr 03
I'm curious to know what everyone thinks of the element in the kiln
bottom. Paragon does not offer that as a standard feature, because kiln
wash falling onto the kiln bottom can ruin the element. Also, the
element limits where you can place the posts on the floor of the kiln.
Sincerely,
Arnold Howard
Paragon Industries, L.P.
www.paragonweb.com
From: Linda Ziesmer
> I'm finally getting ready to order my first kiln (yea!) and would
appreciate
> any feedback about the pros and cons of ordering the optional powered
> bottom. I'm looking at the L&L J2927 with 3" walls. It is 10.17 cu.
ft. I
> essentially intend to fire bisque and glaze to cone 6. The L&L FAQs
state,
> "We recommend this option for a few different reasons: 1) If you are
firing
> very dense loads such as tiles. 2) On very large kilns such as the
T3400
> Series, where you could get a cold spot in the floor, a powered bottom
will
> improve uniformity. 3) To decrease cycle time and add KW to the kiln -
not
> normally an issue with ceramics but it can be for some industrial
processes.
> 4) To increase the temperature rating of a J23 or J2918 kiln. 5)
Another
> benefit of a powered bottom is that it increases the element life by
> allowing all the elements to work less hard to achieve the same
results.
>
> I'm not planning on firing tile or especially dense loads (although
I've
> learned never to say never) and reasons 2-4 don't seem to apply, so is
added
> element life enough of a benefit to justify the added expense up front
as
> well as the ongoing operating costs? Are there other reasons to
consider a
> powered bottom?
>
> Thanks for helping me sort this through,
> Linda
> lziesmer@umich.edu
Paulette Carr on fri 4 apr 03
Greetings, Arnold!
As you may remember, I was having trouble placing posts on the floor of my
2728 ConeArt kiln which has elements in the bottom, without severely damaging
the surface of the soft brick. The problem seems has been resolved. First,
and most important, ConeArt replaced the bottom of my kiln (many thanks to
Ernest!!! from Shimpo). After firing the kiln empty twice (to ^020 and to
^1 to condition the elements), I very carefully painted those areas on the
bottom of the kiln where the posts would stand (directly above the legs of
the kiln stand) on the area outside the first "circle" of elements in the
bottom with Ron Roy's kiln wash recipe (80% alumina hydrate + 20% ball clay +
[my own modification, here] 2% Veegum Cer: sieved twice and added glycerin
for brushing and refired to ^04 without furniture. I fire to both ^04 and
^9. Since the posts no longer span the elements (I now arrange them
differently), and sit only on the kilnwashed areas (they are kiln washed,
too) they do not stick to the floor, and my floor is not damaged when I want
to remove the bottom shelf to vacuum the elements before reloading.
I also have a small Paragon, and like it, but from my experience, having
elements in the bottom is a plus -- helps to even out the temperature in
kiln, along with the 3-thermocouple firing program, and the kiln vent, and a
slow firing program. I do fire dense loads with tiles, and more open loads
with other ware. You have to know something about the density of your load
to find the correct maximum temperature and hold in order to achieve the cone
firing that you want -- I do have to vary the program for the type of load I
am firing.
If Paragon does design one, Howard, move the outer circle containing the
element, well away from kiln wall, so that kiln posts can be easily
positioned. I do not use kiln wash directly on the shelves (but rather
biscuits and firing rods that are coated with kiln wash), so that I can flip
my shelves. As I understand it, many people do not even unload the bottom
shelf once it is positioned, hence I wouldn't think that the kiln wash would
fall into the elements. Proper warnings should prevent problems.
To Linda, I would say, buy the most that you can afford, particularly with
regard to flexibility, because you don't want to be limited in the future by
what you cannot do (i.e., fire loads of tiles). Whatever kiln configuration
you eventually settle upon, you will learn to work with the nuances of that
kiln. I don't know anything about the L&L kiln you are planning to buy, but
I am sure there are Clayarters who do own one, and can better advise you here.
My best,
Paulette Carr
St. Louis, MO
<From: Arnold Howard
I'm curious to know what everyone thinks of the element in the kiln
bottom. Paragon does not offer that as a standard feature, because kiln
wash falling onto the kiln bottom can ruin the element. Also, the
element limits where you can place the posts on the floor of the kiln.
Sincerely,
Arnold Howard
Paragon Industries, L.P.
www.paragonweb.com
>>
Concepts in Clay on sun 6 apr 03
In a message dated 4/3/2003 6:10:15 PM Eastern Standard Time,
arnoldhoward@ATT.NET writes:
> I'm curious to know what everyone thinks of the element in the kiln
> bottom. Paragon does not offer that as a standard feature, because kiln
> wash falling onto the kiln bottom can ruin the element. Also, the
> element limits where you can place the posts on the floor of the kiln.
>
Arnold
I personally would not want to have to be worried about dropping glaze or ???
on an element in the bottom of my kiln. I also think I would lose some
capacity and I can't afford to lose any. Just my personal thoughts.....
Bobbi in central PA
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