Craig Martell on fri 12 jan 01
Hi:
I was going to send this the other day and I lost the original post and
forgot who axed. Sorry!
As far as wrapping a cooling electric with something that will slow the
cool I have a couple of thoughts. You could use ceramic fibre but you run
a risk of inhaling this stuff and it will eventually do you harm. Might
not take as long as some think. Another thing about doing that is heating
the stainless jacket and electrical boxes and all the components. This
could cause some problems too. It will definitely discolor the stainless
and perhaps weaken it too.
You could just downfire with a controller or digital pyrometer. This will
cost more in terms of energy consumption and electric bills. The results
might be worth the extra cost though. One of the big drawbacks of using a
kiln with only 2 1/2 or 3 inches of insulation is this quick cool
thing. Electric firing will produce glazes that rival reduction and the
atmosphere isn't the big deal. It's the quick cool. There isn't any time
for growth of crystals and the glazes will sometimes lack depth. I am, of
course, speaking about firing profiles where you bring the kiln up to
temperature and shut down and let it cool on its own. Crystal glazers and
others who monitor the cool don't do that.
One thing that I did to an electric that I was firing to cone 10 was to add
an inch of AP Green Insblok 19. I took the stainless off the kiln and cut
full strips of Insblok to cover the exterior of the kiln from top to
bottom. I also added fiber blanket to the floor outside the kiln. I used
expanded metal and put a layer of fibre over that and put the floor on
top. I added 2600 degree fibre to the underside of the lid to lessen heat
loss there too. This was about 15 yrs ago and at that time it cost about
350.00 to do the whole job. It took me two days to do the work but I'm
slow. The results were certainly worth the effort. I could fire the kiln
to cone 10 in about 11 hrs. I would shut down about 7pm and there would
still be red heat the next morning. Lots of micro crystals in the glazes
and usually no pits or pinholes. This was a 16 cubic foot oval kiln by the
way.
regards, Craig Martell in Oregon
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