WOODFIRING
THE KIRKWOOD KILN
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published in Ceramics Technical (AU) 2004 Vol.
18.
At first glance, this looks like a small and somewhat
simple woodfiring kiln. In fact it is small but in wood
kiln design terms, it is simple, yet very complex in
many ways. The kiln was made for Mr. Gill
Mallinckrodt (PA). We wanted a wood fired kiln that
was small and simple to fire with ergonomic issues
in mind, no stooping over, bending or lifting heavy
loads. It was made to fire often, as to lessen to down
time between firings so glaze and clay experiments
could be done and repeated often. The kiln had to
be easy to maintain as well. It had to be able to be
fired with ease by both experienced and
inexperienced woodfiring potters. The kiln had to
accommodate the use of spilt or unsplit wood and
the door pulley system had to be set so the doors
would lift with little or no weight resistance. Lastly,
the kiln had to be used for a mix of glazed or
unglazed work and could not spew forth heavy black
smoke when firing in reduction.
This wood kiln is a tube style kiln with a two brick
step up in the middle to separate the tube into two
stacking areas. The grate is a two step grate so that
the wood lies at a 45 degree angle in relation to the
floor. Many air ports are provided to allow as much
or little air for combustion as desired. This helps
control atmospheric conditions within the kiln.
Between the two stacking areas, a small stoke port
can be used in case one would like to side stoke the
kiln. This feature is optional and not always used.
The exit flues lead into the collection box area at the
base of the chimney stack. This area helps the
smoke and expended gases from combustion mix
with air before exiting the chimney stack. Passive
dampers are the main flame velocity control and are
located in the middle of the collection box as well as
all the way around the sides of the collection box
structure. A set of active dampers are located at the
back of the exit flues inside the collection box. We
did this so we could seal the kiln tightly when the
firing was finished. This helps keep the heat in the
chamber itself instead of letting it go on into the
collection box. This ensures the kiln stays hot for
many days and actually, more than a week before
unloading. Crystal structures often appear on this
slow cooling cycle.
This kiln can be salted if desired. There is
also options for firing with oil, sawdust or just
about any combustible fuel. Lastly, the
chimney on this kiln is rather small in
comparison to its size, but we made it that
way and used techniques that ensure it will,
and does, draw well under adverse conditions.