kiln question

On Mon, 4 Aug 2003 10:23:09 +0800, "A&V"
wrote:

Hi,
I have bought second-hand Duncan top loader kiln, fitted it with a automatic
controller and bisque fired it for the first time last night. I was
surprised how hot the outside of the kiln got - I burned my fingers when
inside temp was still under 300 deg.Celsius.
Front loaders I normally fire don't get that hot... I might have safety
issue as the kiln is on my driveway. Also, it is cooling down quite quickly
which makes me think of energy loss issues. Would it be possible/practical
to somehow extra-insulate kiln?
Any thoughts?
Cheers,
Andrea


Yes - get it off of your drive before it rains (you don't say where
in the world you are, Aussie I assume) and you electrocute yourself
........... :-| Should really be fitted and stand in a permanent place
....... Sounds like a breakdown in the internal insulation somewhere,
although 300 (even inside) is quiet warm !!

Hi Andrea,

Duncan kilns are designed to fire only slip cast ceramics. As such, they are
designed to be heated up quickly and cooled down quickly, because slip cast
pieces can stand this treatment. I assume that you are using a programmable
controller with a slow heating cycle for firing pottery, so there will be a
lot of heat loss because the kiln is not designed for slow firings. After
all, the brick is only 2 1/2 to 3 inches thick - whereas a kiln for pottery
uses 4 1/2 inch wall thickness minimum.

You cannot readily add extra insulation to one of these kilns.

Sorry, but horses for courses.

Dave




On Mon, 4 Aug 2003 10:23:09 +0800, "A&V"
wrote:

Hi,
I have bought second-hand Duncan top loader kiln, fitted it with a
automatic
controller and bisque fired it for the first time last night. I was
surprised how hot the outside of the kiln got - I burned my fingers when
inside temp was still under 300 deg.Celsius.
Front loaders I normally fire don't get that hot... I might have safety
issue as the kiln is on my driveway. Also, it is cooling down quite
quickly
which makes me think of energy loss issues. Would it be
possible/practical
to somehow extra-insulate kiln?
Any thoughts?
Cheers,
Andrea

Yes - get it off of your drive before it rains (you don't say where
in the world you are, Aussie I assume) and you electrocute yourself
.......... :-| Should really be fitted and stand in a permanent place
...... Sounds like a breakdown in the internal insulation somewhere,
although 300 (even inside) is quiet warm !!

Driveway (and kiln) are protected from rain, and it is intended as a
permanent place.
My safety concerns are more to do with someone burning themselves than
electrocuting as the electrician connected the kiln and we made sure all the
switches are for the outside, all the wires thermally resistant etc etc.
(it is not really exposed to unsuspected public,but curiosity...)
My address tells you I am indeed Aussie (from Perth - it is raining!)
I probably should of mentioned that the kiln is made of firebrick with a
thin (in my opinion) stainless steel "drum" around it.
thanks for your comment,
Andrea

On Mon, 4 Aug 2003 16:35:40 +0800, "A&V"
wrote:

Yes - get it off of your drive before it rains (you don't say where
in the world you are, Aussie I assume) and you electrocute yourself
.......... :-| Should really be fitted and stand in a permanent place
...... Sounds like a breakdown in the internal insulation somewhere,
although 300 (even inside) is quiet warm !!

Driveway (and kiln) are protected from rain, and it is intended as a
permanent place.
My safety concerns are more to do with someone burning themselves than
electrocuting as the electrician connected the kiln and we made sure all the
switches are for the outside, all the wires thermally resistant etc etc.
(it is not really exposed to unsuspected public,but curiosity...)
My address tells you I am indeed Aussie (from Perth - it is raining!)
I probably should of mentioned that the kiln is made of firebrick with a
thin (in my opinion) stainless steel "drum" around it.
thanks for your comment,
Andrea


Hi Andrea,

I think Dave Coggins has your answer .............

Perth, Aussie, Rain ???? ........... NEVER !!!!

Try England and see how you get on with a kiln on your drive :-))

Still at least we are good at cricket .................. :-||||

Hi Andrea,

There can be a lot of difference in firing slip cast (usually called
"ceramics") and hand (wheel) made pottery. If you fire both in the same
kiln, you will need to fire as for pottery, that is slow firing up to 600
deg C for bisque to burn out all the organics and water, to avoid explosions
and fire properly. By slow, I mean 75 to 125 degrees C per hour ramp rate,
depending on how thick the pots are. Slip cast pieces, being very thin
(usually) and free of many of the organic materials of unprocessed pottery
clay, can be heated at a much faster ramp rate.

Slip cast "ceramic" pieces are usually fired to a high bisque (1060 -1100
deg C) to vitrify, then a lower glaze temp ( about 1000 deg C). Pottery is
usually fired to 1000 deg C for bisque (so the glazes will stick) then high
fired (1080 to 1280 deg C) for glazing and vitrification (making the clay
waterproof).

Hope this clears thing up a bit for you.

Dave

"A&V" wrote in message
...

Thanks Dave & Penny,
I never knew that there was difference in firing slipcast and thrown pots.
Would you mind telling me how would you fire?
I tend to do bit of both, but usualy fire together.
thanks,
Andrea

f you fire both in the same
kiln, you will need to fire as for pottery, that is slow firing up to 600
deg C for bisque to burn out all the organics and water, to avoid explosions
and fire properly. By slow, I mean 75 to 125 degrees C per hour ramp rate,

i think you ahve just answered for me some of the problems i was having last
year firing my students work. I had a number of thicker pieces blow up. My
principle wanted em to fire it as quickly as i coudl to save energy


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lunch. Liberty is a well-armed lamb contesting the vote."

-- Benjamin Franklin, 1759