Heat Balance, Continued from Page 4

The kiln reaches maximum temperature when the heat going in
equals the heat going out. It’s a heat balance. The more heat you put
in, the hotter it gets until the kiln walls radiate out as much heat as the
elements produce inside the kiln. The kiln cannot get any hotter, and
this is almost the point we reached in the first firing. The kiln room
was very hot as the kiln radiated so much heat. An oval kiln has more
surface area per cubic foot of interior space compared to a circular kiln
hence more heat loss.

Our initial reaction was to insulate the kiln with the maximum
amount of ceramic fibre blanket, at least two inches, possibly more.
Plan B was to buy even more elements from Seattle Pottery Supply
which would have a bigger output.

I went to Inproheat in Vancouver for ceramic fibre and shared
my kiln story with them. This is where it pays to consult with the Working on the kiln lid.
salesman. He calculated the temperatures in the wall of the kiln at
varying distances through the wall itself. He calculated how two inches
of insulation would affect the outside temperature of the kiln. Based

on an inside temperature of 2195°F, and a three-inch soft brick wall,
the original outer skin of the kiln would heat up to 1150 deg F. Red
hot. One-inch-thick fibre was all I needed, which made the steel skin
approx 750°F. Ceramic fibre is such a good insulator that the final
surface temperature would be around 200°F.

So we wrapped the kiln. I don’t know if anyone has done this before,
but it was a long process. It took three days to wrap it, one box of 1
inch fibre, two sheets of 4’x 8’ aluminum and lots of stainless steel
screws. We put two inches of fibre on the lid too.

‘The result was stunning. We increased the rate of rise from 20°F/hr
at 2160° to 120°F/hr right up to 2195°F. The cones were even all over
the kiln, cooling is a little slower but the results are excellent.

Tt may have taken a month, on and off, to finally complete the great
kiln wrap but it’s a kiln that we can rely on now. Would I do it again?
Maybe. Even though something is initially free, it’s bound to cost you
something in the end, if not financially, then in stress. Anything can
be fixed but sometimes it’s just easier to spend the money on the most
reliable option and make more pots instead with the time saved.

Clive Tucker is a ceramic artist working in Port Moody. He also offers

kiln repair services. See his work at www.clivetuckerceramics.ca

Sarah graduated from Kootenay School of the Arts
(KSA) in 2006 and is a 2008 BC Creative Achievement
Award winner. She has her own studio practice and is
presently selling her work in the Gallery of BC Ceramics
in Vancouver.

KSA offers a 2-year diploma in Art Craft & Design with
a Major in Clay. The program focuses on hands-on
training with an emphasis on studio practice and is
transferable.

APPLY NOW for 1st year or direct entry into 2nd year.
Applications accepted for September or January entry.

Selkirk [@] College

COLUMBIA Potters Guild of BC Newsletter - November 2009 5