Jonathan Pennington on thu 2 aug 01
I've decided to build a kiln for sawdust firing after having done it a
couple times with mixed but interesting results. I've been building up
a kiln out of IFB, but it wears away easily, and I'm sick of running
around filling holes with clay before all my fuel burns to fast.So, I
wanted to run this design idea past the gurus to see what everyone
thinks.
Here's my idea: Use firebrick (hard brick) to build a chamber about 3
bricks deep x3 bricks wide. Bricks will lay down flat and the base
will be two bricks thick. This way, the primary insulation will be 4in
(or whatever firebrick width is). Then, I want to take all the soft
brick I have and cut it in half- making approx. 9x4x1in bricks to line
the exterior and create sort of an IFB shell. I'm estimating a height
of 15 bricks, but I have to see how fesible different heights are with
the stand (Although I'm 6'3", so I'm not too worried about it being
too high). After researching and assessing my needs right now, I'm not
planning on building a gas kiln anytime soon. This means I don't mind
using these bricks for this purpose, instead of paying for fibre or
something and having the bricks sit idle.
For a top, I'll use kiln shelves and place a layer of IFB on top of
them. The shelves will have slits in them, so that I can adjust the
airflow out the top by pulling back the bricks that are covering them.
I'm planning on spraying the inside with ITC as well to get a bit more
insulation if I need it in the future- this maybe overkill, we'll see.
In addition, I'm going to play with the idea of putting a grill over
the top to utilize some of the escaping heat for cooking. If I do
this, I will channel the smoke out the back end somehow.
The kiln will be mortared together- and I don't know with what. Maybe
a storebought air set high temp mortar, maybe a mixture of fireclay
and other stuff such as Olsen and others have talked about. I'm
looking for suggestions here. Cheap as possible, but I do want it
mortared, because it'll be built onto a locking wheeled cart so I can
move it into my driveway to fire it. I'm also planning on sheet
metal/banding the sides, but that's just for looks and to protect the
IFB which might get beat up when I move it around if it's uncovered.
I'm planning to place holes near the bottom on the sides. These I'll
be able to cover with peephole covers that I'll make out of stoneware.
This way I can control the amount of air into the system easily. I'm
thinking 3 holes on each side. I might have holes about half way up as
well, but that can be done later if needed. I'm also placing a hole in
the bottom- one that I can stick a propane torch into to start some
heavy wood and coals burning on the bottom (later plans). There'll be
a hole for a pyrometer as well about 3/4 of the way to the top.
I'm planning to use small branches and stuff in the bottom to create
rather hot coals that will burn down slowly and heat the interior a
good bit more than just the burning material will. If I do this,
there'll basically be a kilnshelf and stilts on the bottom with
firewood/coals/kitchen sink, under that shelf so that the ware isn't
directly on top of this burning material. This is my way to sort of
blend a sawdust and wood-fired kiln design. I know that the burning
coals on the bottom will ignite the surrounding sawdust and burn up
instead of down. This would be an "end-fire" addition to the process
to raise the internal heat and further reduce the ware as well as come
closer to a real firing temp for earthenware. I haven't yet decided on
a bottom door or loose brick through which I can add more wood/fuel. I
may end up building something closer to a firebox. I'm still playing
with the design.
I realize that common practice doesn't have people building such a
substantial sawdust kiln (it's a garbage can firing technique) but I'm
thinking about using that to improve the heat on the inside to extend
a bit beyond the range of traditional sawdust firing. I'd like to be
able to get a good amount of heat inside, more than with a garbage can
or built-up solution. This way, I can do a bit more experimentation
with low-temp glazes and other burnables.
Just wanted to throw my idea out there and see what everyone thought.
-Jonathan
"There are no pots, there is only clay." -me
jay s. gertz on fri 3 aug 01
Jonathan,
I too am planning on constructing a small sawdust kiln. Yer idea sounds
good to me! I'm not sure if there's a right or wrong way to build one.
I've recently looked at a book by Jane Perryman entitled: Smoke-fired
pottery and there's a raft of ideas within its pages.
jay
jay s. gertz
(jgertz@bulldog.unca.edu)
(828) 251-6627
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