Larry Kruzan on tue 20 apr 10
Hi All!=3D20
Shortly I am going to begin filling a large order of small items. In order =
=3D
to get the best loading of the kiln I need to make a lot of specialized kil=
=3D
n setters that I will extrude.=3D20
I suspect that my regular claybody (a smooth ^10 stonware)=3DC2=3DA0would w=
ork =3D
for making these setters but since each setter will be fired up to 20 times=
=3D
to ^10 reduction, I'm a little concerned about long term durability.=3DC2=
=3DA0=3D
=3DC2=3DA0=3D20
So I am looking for a claybody that hold up to these firing rates. Would ad=
=3D
ding grog or mulite to my existing bady make it more durable? Or do you hav=
=3D
e a body formula I could use?=3D20
Thanks,=3D20
Larry Kruzan=3D20
Lost Creek Pottery
David Hendley on wed 21 apr 10
Hey Larry,
I make all my own kiln posts (it's a great use for the extruder).
As for what clay to use - think refractory, avoid any kind of flux.
Your regular claybody would be a poor choice since it is fluxed
to approach vitrification at cone 10.
I save all my old, broken, or wrecked insulating firebricks and
crush them into coarse grog consistency. When kiln building, I
also save any brick dust produced when sawing IFBs.
I make sure everything will pass through window screen, to
keep out any huge chunks.
I then add as much of this as possible to fireclay, to produce
my kiln furniture claybody.
The balancing act is adding as much firebrick grog as possible
while still having a reasonably plastic extruding body.
I usually end up with, I would guess, about 50/50 by volume
of IFB grog and fireclay, and then add about 20% ball clay
to aid in plasticity. I also add about 5% alumina hydrate. It is
expensive, but I think makes more durable kiln furniture,
especially for my wood-fired kiln and its corrosive ash laden
atmosphere. If you only need the setters to last 20 or fewer
firings, don't bother.
You need all the plasticity you can get, so wet mix everything
into a thick slurry and then dry to plastic consistency on plaster
slabs or by some other means.
If you don't have any IFB pieces or dust, Arnold at Paragon
Kilns will sell you some, or just use any coarse grog available
to you. Again, load up fireclay with the grog, adding ball clay
as needed to produced a reasonably formed extrusion.
David Hendley
david@farmpots.com
http://www.farmpots.com
----- Original Message -----
Shortly I am going to begin filling a large order of small items. In order
to get the best loading of the kiln I need to make a lot of specialized kil=
n
setters that I will extrude.
I suspect that my regular claybody (a smooth ^10 stonware) would work for
making these setters but since each setter will be fired up to 20 times to
^10 reduction, I'm a little concerned about long term durability.
So I am looking for a claybody that hold up to these firing rates. Would
adding grog or mulite to my existing bady make it more durable? Or do you
have a body formula I could use?
Lee Love on wed 21 apr 10
John Conrad's kiln furniture recipe:
http://www.potters.org/subject04715.htm
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
=3D93Observe the wonders as they occur around you. Don't claim them. Feel
the artistry moving through and be silent.=3D94 --Rumi
ivor & olive lewis on fri 23 apr 10
"Handbook for Australian Potters", ISBN 0-454-00448-6, has a chapter (pp
206-212)on this process. Page 210 in gives several mixtures based on
Australian raw materials.
Consider the qualities you require when selecting raw materials for service
in your kiln. Refractoriness, Load bearing strength at high temperatures,
resistance to warping and so on.
For example, will any furniture take the brunt of the flames during heating=
.
If this is the case it may pay to consider mixtures that are low in fluxing
agents that could cause your mixture to become pyroplastic at the maturity
value of the ware you are firing. So, beefing up a regular clay body that
vitrifies at your firing temperature with grog might be unwise,
disadvantageous.
Where a grog is to be used avoid Silica. Notorious in its differing guises
for their phase changes. These could lead to disaster. Sillimanite, Mullite
or Kyanite are preferable.
All the best,
Ivor Lewis,
Redhill,
South Australia
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