Re: kiln question

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

possible/practical

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 .................. :-||||

Don't know about Duncans but mine is a top loader also (name escapes me at the moment - brain freeze!). It gets VERY hot when firing and in fact I burnt a hole through a winter coat sleeve last winter. My old kiln, I could lift the metal peep hole covers no problem with a pair of oven mitts or a cloth. Tried it with the new kiln a burnt the sleeve to my finger (ouch). My kilns are in my garage ( not attached to the house) and the kids are not allowed in there when they are firing, nor do I work in there. No venting and the heat!!!!!! Plus I am afraid of burning myself. I have never worried about extra insulation as they work fine as they are and take about 5 hours for a ^06 bisque and about 9 or 10 hours for ^6. Cool down in about 12 to 15 hours - still hot but unloadable.

~~~~~~~~~~~~ Penni Stoddart of Penelope's Pots Full Time Education Assistant, Part Time Potter

Sometimes we just need to remember what the rules of life really are... You need only two tools: WD-40 and duct tape. If it doesn't move and it should, use WD-40. If it moves and shouldn't, use the duct tape.

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

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

"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -- Benjamin Franklin, 1759