David Hendley on wed 5 may 04
A couple of people had questions about my homemade kiln pots.
My extruder die is 2" square. This results, with shrinkage, in kiln
posts that are about 1 3/4" square. This is about average size for
kiln posts. The commercial ones I have are 1 1/2" and 2". I would
never want the finished posts to be smaller than 1 1/2" square, no
matter what kiln they would be used in. I like square pots (compared
to triangular or round) because they stack better when not in use.
The alumina hydrate coating really helps them repeal the ashes in
my wood fired kiln, but I would still add the coating even if I used
a gas or electric kiln.
I break up the already-broken insulating fire bricks with my
"monster maul" - a wood splitting maul with a 12 pound head, by
dropping it on the bricks.
When the pieces are about marble sizes, I get a piece of flat steel
plate and roll it over the chuncks - this serves to break down only
the pieces that are still too big. Wear a respirator when you break
IFBs.
By the way, for my electric kiln, used for bisque only, I made
the kiln posts out of my regular stoneware clay, and fired them
only to bisque temperature. This works fine, but since I cut them
to length using the lath for my high-fire posts, they did not shrink
as much and are a little longer than standard measurements.
Actually, I like them being a little long - gives you a little extra
space, like setting your watch a little fast gives you a little extra
margin to be on time.
David Hendley
david@farmpots.com
http://www.farmpots.com
> >
> > Anyway, here is how I make them:
> > I use a 2" square hollow extruder die, remove the center section and
> > replace it with a small washer - so the resulting extrusion is mostly
> > a solid square, but with a small hole in the center.
> >
> > The "recipe" for kiln posts is crushed insulating fire bricks and
> > fireclay.
> > Crush the bricks to "window screen mesh", add enough clay to make
> > the mixture extrudable (probably about 1/3 by volume or 1/2 by
> > weight). For wood or salt kilns, add 10% alumina. Don't worry about
> > "drag marks" when extruding, there will be some.
> >
> > Cut some lath boards the proper length for each length of post (add
> > about 10% to the length you want to end up with). Use these to
> > cut each post to length. If they are a little long or short of standard
> > measurement it doesn't matter, as long as they are consistent.
> >
> > After the posts are cut to length, roll them in a tub of hydrated
> > alumina, so all 6 surfaces are coated. Use a stamp to impress the
> > length measurement on each post.
> >
> > Fire to your top kiln temperature before using them to support
> > kiln shelves.
> >
> > I also use firebricks that I got from the firebrick factory before
> > they were fired as kiln posts. If you have a factory nearby, you
> > might consider this.
> > I cut them to length with a miter saw. Use an old dull blade - it
> > will be very dusty, but easy to cut. I made soaps, half-soaps
> > (4 1/2" tall), 7" tall soaps, and 1/8 bricks, which use the thickness
> > of the brick (2 1/2") as the critical measurement.
> > Before firing, I dunked them in water and then in a bucket of
> > kaolin/alumina kiln wash.
David Hendley on thu 24 jan 08
Like Lili, I have been making all my own kiln posts for many
years. I remember the 1978 CM article on making your own
kiln furniture because it was written by Elmer Taylor, the
professor at the Univ. of North Texas, where I had gone to
school a few years earlier.
The suggestions in the article for making your own kiln
shelves are not so good. I would not try to make my own.
Unlike with posts, you just can't make a kiln shelf as good
as a manufactured one.
I would recommend making your own posts to everyone.
Anyway, I, of course, extrude my kiln posts:
I use a 2" square hollow extruder die, remove the center section
and replace it with a small washer - so the resulting extrusion
is mostly a solid square, but with a small hole in the center.
My extruder die is 2" square, so this results, with shrinkage, in kiln
posts that are about 1 3/4" square. This is about average size for
kiln posts. The commercial ones I have are 1 1/2" and 2". I would
never want the finished posts to be smaller than 1 1/2" square, no
matter what kiln they would be used in. I like square pots (compared
to triangular or round) because they stack better when not in use.
My "recipe" for kiln posts is crushed insulating fire bricks and
fireclay. I break up already-broken insulating fire bricks with my
"monster maul" - a wood splitting maul with a 12 pound head, by
dropping it on the bricks.
When the pieces are about marble sized, I get a piece of flat steel
plate and roll it over the chunks - this serves to break down only
the pieces that are still too big. Wear a respirator when you break
IFBs.
Most potters have old broken bricks laying around, and this is a
great use for them. Of course you could always simply use
coarse grog instead of crushed bricks.
I add enough clay and water to make the mixture extrudable
(probably about 1/2 by volume clay). For wood or salt kilns,
add 10% alumina, to help them resist glaze build-up. Don't worry
about "drag marks" when extruding - there will be some with
such a coarse mixture.
Be sure you have "Music to Extrude By", by The Extrudinaires,
playing on your CD player, as you squeeze out the posts.
Cut some lath boards the proper length for each length of post (add
the amount the mixture will shrink, about 10%, to the length you
want to end up with). Use these to cut each post to length. If the
posts end up a little long or short of standard measurement it
doesn't matter, as long as they are all the same.
After the posts are cut to length, roll them in a tub of hydrated
alumina, so all 6 surfaces are coated. Use a stamp to impress the
length measurement on each post.
The alumina hydrate coating really helps them repeal the ashes in
my wood fired kiln, but I would still add the coating even if I used
a gas or electric kiln.
Fire the posts to your top kiln temperature before using them
to support kiln shelves.
By the way, for my electric kiln, used for bisque only, I made
the kiln posts out of my regular stoneware clay, and fired them
only to bisque temperature. This works fine, but since I cut them
to length using the lath for my high-fire posts, they did not shrink
as much and are a little longer than standard measurements.
Actually, I like them being a little long - gives you a little extra
space, like setting your watch a little fast gives you a little extra
margin to be on time.
I also use firebricks as kiln posts. I got them from the firebrick
factory before they were fired. If you have a factory nearby, you
might consider trying this.
I cut them to length with a motorized miter saw (chop saw). Use
an old dull blade - it will be very dusty, but the unfired bricks are
easy to cut.
Do this outside! on a day with a breeze! while wearing a real
respirator (not a disposable pollen mask)!
I made soaps, half-soaps (4 1/2" tall), 7" tall soaps, and
1/8 bricks, which use the thickness of the brick (2 1/2") as the
critical measurement (great for plates). Before firing, I dunked
them in water and then in a bucket of kaolin/alumina kiln wash.
As with the extruded posts, fire to top temperature before they
are put into service as posts.
Happy extruding,
David Hendley
Maydelle, Texas
david(at)farmpots(dot)com
http://www.farmpots.com
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