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wood burning kiln

updated mon 15 dec 97


THE POTTER on sun 14 dec 97

Pat, I don't know this particular kiln but have built and rebuilt the Olsen
fast fire several times(salt!). 1) Start level. 2) Build up your corners
ahead of your run of wall and level between them then fill in. Keep level.
If you are using hard brick then use a fireclay mortar to bed in the bricks
but if insulating brick lay them up dry. If you are bothered about joints
then stagger the outer layer of brick so the joints don't line up through
the wall. The stoker will appreciate good insulation so allow 2 layers of
brick and its a lot easier to keep both layers flat unless you're on a tight
I assume that with all that block and brick the fire boxes are not under
the kiln but it is worth considering using hard brick for the reveals at
firemouths from a wear point of view as well as to line the firebox itself.
Where a firebox is underfloor the wall over firemouth openings is best
carried on an arch. The kiln floor behind this can be a kiln shelf but if
this is carried through to the outside to support the wall it is liable to
crack due to temp. difference.
It may be convenient to build within the metal frame but be careful to
leave expansion joints. It is also important to leave fair faces at all
openings and to keep both sides of an opening in the same plane. It is very
convenient to be able to fit doors over firemouths to control draught and
you will be surprised at how small an air intake area you will need.
For the arch you can use either a full former or one of about 12" to
start off after which the bricks just key in. To make a taper on the bricks
I did the following: 1) Subtract the inner from the outer diameter of the
arch. 2) Divide this difference by the no. of bricks in the span of the arch
and halve the answer to find how much needs to come off each side of each
brick. 3) Make 2 thin wooden slats of this thickness. 4) Make a trough to
hold several bricks flat and end to end. 5) Place one slat in the trough
against one wall and place the bricks on top. 6) don goggles mask and any
other dust proofing you have and outside in a good breeze grind off the
protruding face of brick with an anglegrinder and brick grinding ( not
cutting ) blade. 7) Repeat for the other side but this time with 2 slats
underneath. I strongly recommend that you make full size card templates of
your tapered bricks to check your calculations (and my method) and lay them
out to check the fit.
After the arh is in place, dry laid, the walls can be continued, in 4"
block for economy, above the spring and a stiff mix of vermiculite 9, Cement
1 laid over the top to add insulation.
Paint any iron work before assembly with heat resistant paint at least
on the inside surfaces.