JoleeRene on tue 10 sep 96
I am attempting to raku flat wall hangings. They are round, about 18" in
diameter. I fire to 1800. I have had 12 firings and 12 failures - they
all broke into two or three large pieces during the firing itself. I
don't know if its the way they are supported during the firing, or what.
This is a commercial raku clay body I have used for several years and
believe that's not the problem. I fire them flat on the kiln shelf.
Any one have any thoughts?
Also - For removing the pieces - I thought about making a "basket" that
the piece could be fired in and then the basket lifted out and placed in
the reduction material. Does anyone know what type of material I should
experiment with for this? It would have to be an open weave in order to
work in the reduction process.
Thanks, in adance, for your creative & informed responses.
Dannon Rhudy on wed 11 sep 96
>----------------------------Original message----------------------------
.. I fire them flat on the kiln shelf.
>
>
>
>Also - For removing the pieces - I thought about making a "basket" that
>the piece could be fired in and then the basket lifted out and placed in
>
>You might try elevating the pieces on some bricks or kiln furniture, so that
they are not lying flat on the shelf. Space them for good support, leave room
for heat circulation.
Instead of making a "basket" to fire them in, make a special pair of tongs
or get a welder/machine shop to alter a pair so that the ends make a large
circle. Slip these special tongs under the piece, and lift that way. I made
a pair that works well for large platters.
Further, consider the thickness of the clay. If too thin, it is more fragile at
maturation heat.
Dannon Rhudy
dannon@koyote.com
marilyn fenton on wed 11 sep 96
cooler pieces might be cracking when put into the kiln
you notice them when you pull them out. First place a
cool shelf into the kiln and then your piece.
Paula Coleman on wed 11 sep 96
>----------------------------Original message----------------------------
>I am attempting to raku flat wall hangings. They are round, about 18" in
>diameter. I fire to 1800. I have had 12 firings and 12 failures - they
>all broke into two or three large pieces during the firing itself.
I have experienced this same problem with large (12 inch) tiles I made at a
tile factory. To solve this problem we did two things. First, we coated
the shelf with a bed of grog. As the piece shrinks, the grog will act as
ball bearings so that it can slide more easily across the shelf. Second, we
built a barrier around the tiles with some pieces of soft brick to prevent
the edges from heating more quickly than the center. I hope this helps.
--------------------------------------------------------------------
Paula L. Coleman Email: potter@comcat.com
Ceramic Artist Web: http://www.comcat.com/~potter/
Bucks County, PA, USA
Vince Pitelka on wed 11 sep 96
>I am attempting to raku flat wall hangings. They are round, about 18" in
>diameter. I fire to 1800. I have had 12 firings and 12 failures - they
>all broke into two or three large pieces during the firing itself. I fire
them flat on the kiln shelf.
Firing large flat pieces flat on the kiln shelf is risky. The kiln shelf
insulates the center of the form from the heat while the edges get full
heat. I have had very good luck firing such shapes on clay wads or on thin
insulation-brick shims. The larger the shape, the more even the support
must be. For pieces such as yours, I would use a network of at least a
dozen clay wads giving even support overall. This will allow the heat to
circulate evenly below the piece. Another option would be to fire the
pieces standing on edge. If they are very thin, they could warp. Also, if
one surface is glazed, the glaze will be more likely to run, but otherwise
this might work well. They could be leaned against some standing hardbrick.
Good luck.
- Vince
Vince Pitelka - vpitelka@Dekalb.Net
Phone - home 615/597-5376, work 615/597-6801
Appalachian Center for Crafts, Smithville TN 37166
Terrance Lazaroff on wed 11 sep 96
Firing flat pieces 18" dia. in a raku kiln is difficult because most raku
kiln shelvs are covered with glaze drippings, grog, and kilnwash. They are
definately not smoth. What is probably happening is that the piece cannot
shrink easily. I don't know what to suggest other than laying down a good
layer of grog on the kiln shelf prior to placing your piece down.
As for a basket that may also solve the problem. It would have to be made
from high temp wire. The same type used in an electric kiln. The basket may
assist the flat piece as it shrinks during the firing. It is worth a try.
Let us know how it comes out.
Terry
Elaine J. Walters on wed 11 sep 96
------ =_NextPart_000_01BB9F62.E0D530A0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 8BIT
Hi! Something that might help. I fire all my flat wall hangings on edge, never
flat. I prop them up with soft brick. When I fire them flat they always crack.
I also never use Raku clay, only white stoneware. For some rfeason Raku clay
seems to break and crack more often. I have fewer failures with stoneware.
Hope this helps!
Elaine. Camano Island, WA.
----------
From: JoleeRene[SMTP:joleerene@aol.com]
Sent: Tuesday, September 10, 1996 3:06 PM
To: Multiple recipients of list CLAYART
Subject: Raku Help Needed for flat pieces
----------------------------Original message----------------------------
I am attempting to raku flat wall hangings. They are round, about 18" in
diameter. I fire to 1800. I have had 12 firings and 12 failures - they
all broke into two or three large pieces during the firing itself. I
don't know if its the way they are supported during the firing, or what.
This is a commercial raku clay body I have used for several years and
believe that's not the problem. I fire them flat on the kiln shelf.
Any one have any thoughts?
Also - For removing the pieces - I thought about making a "basket" that
the piece could be fired in and then the basket lifted out and placed in
the reduction material. Does anyone know what type of material I should
experiment with for this? It would have to be an open weave in order to
work in the reduction process.
Thanks, in adance, for your creative & informed responses.
------ =_NextPart_000_01BB9F62.E0D530A0
Content-Type: application/ms-tnef
Content-Transfer-Encoding: base64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------ =_NextPart_000_01BB9F62.E0D530A0--
Phil Davenport on wed 11 sep 96
JoleeRene:
The problem with flat pieces is uneven heating. With this problem comes
breakage. I have discovered that if I would put COLD bricks on the hot
shelf and then put the pot on top of the bricks that I had less cracking.
If you have more that one piece to fire then rotate bricks in and out of
the kiln.
Phiol Davenport
Garland, Texas
On Tue, 10 Sep 1996, JoleeRene wrote:
> ----------------------------Original message----------------------------
> I am attempting to raku flat wall hangings. They are round, about 18" in
> diameter. I fire to 1800. I have had 12 firings and 12 failures - they
> all broke into two or three large pieces during the firing itself. I
> don't know if its the way they are supported during the firing, or what.
> This is a commercial raku clay body I have used for several years and
> believe that's not the problem. I fire them flat on the kiln shelf.
>
> Any one have any thoughts?
>
> Also - For removing the pieces - I thought about making a "basket" that
> the piece could be fired in and then the basket lifted out and placed in
> the reduction material. Does anyone know what type of material I should
> experiment with for this? It would have to be an open weave in order to
> work in the reduction process.
>
> Thanks, in adance, for your creative & informed responses.
>
Jeannine Broadwell on wed 11 sep 96
>>> JoleeRene 09/10/96 06:06pm >>>
----------------------------Original message----------------------------
I am attempting to raku flat wall hangings. They are round, about 18" in
diameter. I fire to 1800. I have had 12 firings and 12 failures - they
all broke into two or three large pieces during the firing itself. I
don't know if its the way they are supported during the firing, or what.
This is a commercial raku clay body I have used for several years and
believe that's not the problem. I fire them flat on the kiln shelf.
--------------------------------------------------------------------------------
Jolee
I've had similar difficulties with flat raku pieces and subsequently
modified my firing procedures as follows:
1) First I preheat the raku kiln with an empty kiln shelf inside.
2) Then I stand three or four kiln bricks (depending on the size of the
ware) on end, on the kiln shelf.
3) Immediately after that, I place the ware on the bricks and begin firing
the ware.
These modifications improve air circulation, decrease the number of
points of contact, and decrease the risk of thermal shock.
*If* your problem has the same cause as mine, you may find these
changes helpful.
jeannine broadwell
st. mary's college of maryland
jabroadwell@osprey.smcm.edu
LOWELL BAKER on wed 11 sep 96
The only addition I would make to the discussion on flat work in Raku
is that; many years ago when I was working with a lot of flat Raku, I
handled the pieces with a hay fork rather than tongs. Simply slip
the fork under the piece and lift to transfer it to the reduction
pit. This prevents the stress of lifting from one point.
I eventually welded up my own lifter to suit each kind of flat ware
we produced.
Lowell Baker
The University of Alabama
Beth Wheeler on wed 11 sep 96
We have had great success with large, flat Raku pieces by building a support
platform with soft brick - so that maybe 3" -5" around the edges is exposed.
This positioning is important for the removal process, which is done with
"fireproof gloves" (obtained through the Grainger Catalogue, aslo wearing
the same type of apron, a respirator, and sometimes welder goggles). With
this process you can gently & quickly place the piece on your reduction
nest and cover with a can. Some of the potters here have completed large
wall pieces that are comprised of several large flat sections.
May be this will work for you too.
At 06:06 PM 9/10/96 EDT, you wrote:
>----------------------------Original message----------------------------
>I am attempting to raku flat wall hangings. They are round, about 18" in
>diameter. I fire to 1800. I have had 12 firings and 12 failures - they
>all broke into two or three large pieces during the firing itself. I
>don't know if its the way they are supported during the firing, or what.
>This is a commercial raku clay body I have used for several years and
>believe that's not the problem. I fire them flat on the kiln shelf.
>
>Any one have any thoughts?
>
>Also - For removing the pieces - I thought about making a "basket" that
>the piece could be fired in and then the basket lifted out and placed in
>the reduction material. Does anyone know what type of material I should
>experiment with for this? It would have to be an open weave in order to
>work in the reduction process.
>
>Thanks, in adance, for your creative & informed responses.
>
katie rose on wed 11 sep 96
>I've had similar difficulties with flat raku pieces and subsequently
>modified my firing procedures as follows:
>
>1) First I preheat the raku kiln with an empty kiln shelf inside.
>
>2) Then I stand three or four kiln bricks (depending on the size of the
>ware) on end, on the kiln shelf.
>
>3) Immediately after that, I place the ware on the bricks and begin firing
>the ware.
>
>These modifications improve air circulation, decrease the number of
>points of contact, and decrease the risk of thermal shock.
i am wondering if it would work as well to eliminate the preheating and
simply put in the additional kiln bricks and place the ware on them at the
outset. that way the piece could be heated slowly and gradually as well as
lessening the points of contact. yes?
thanks.
katie rose
****************************************************
katie rose
raven@sedona.net
"Love is the reflection of God's unity in the world of duality. It
constitutes the entire significance of creation." (Meher Baba)
don jung on wed 11 sep 96
We've been able to fire fairly large pieces (bowls, masks and tiles) about 18"
in raku with a fair amount of success. We try to include the large stuff in the
first firing which is taken up slower in temp. (1.5hrs+). Subsequent firings of
large things are consciously taken up slower as well (~1hr+) and they are
'preheated' next to or on the kiln prior to loading. We also try to stack the
piece in vertically. This is more to maximize space, but we've noticed that a
piece that's stacked flat seems to trap the heat underneath, so the temp and
glaze on top of the piece matures much later than the bottom. This uneven temp
may be causing some stress...no doubt.
The other thing about a support basket...We don't use it for the big stuff but
we do use a wire mesh sort of pan to put small things in that are tough to pick
up with tongs. I suppose you can enlarge and use for bigger things. A chain
link sort of fencing can be made from kanthal wire and shaped into whatever.
Mesh metal sheeting can be used to, but it doesn't last too long. Note: we
usually glaze with a matt raku glaze when in contact with a support, otherwise
it may stick.
have fun
Don
-------------
On Tue, 10
>----------------------------Original message----------------------------
>I am attempting to raku flat wall hangings. They are round, about 18" in
>diameter. I fire to 1800. I have had 12 firings and 12 failures - they
>all broke into two or three large pieces during the firing itself. I
>don't know if its the way they are supported during the firing, or what.
>This is a commercial raku clay body I have used for several years and
>believe that's not the problem. I fire them flat on the kiln shelf.
>
>Any one have any thoughts?
>
>Also - For removing the pieces - I thought about making a "basket" that
>the piece could be fired in and then the basket lifted out and placed in
>the reduction material. Does anyone know what type of material I should
>experiment with for this? It would have to be an open weave in order to
>work in the reduction process.
>
>Thanks, in adance, for your creative & informed responses.
> Sep 1996 18:06:10 EDT you wrote:
Ronald D. Hicks on wed 11 sep 96
I had the same problem when I was on a teaching exchange in Perth, Western
Australia. Their Raku kiln just couldn't fire even or slow enough and I
broke all the platters. With large flat ware, platters or tiles.....it is
very difficult to apply even heat when firing a gas Raku kiln.....even a
small flame flicker heats one side more that the other....and if you turn
it up past that, then it heats the outside rims too quickly. To solve my
problem, I started preheating them quite hot in an electric kiln and would
pull them out, take them to the Raku kiln and then begin the glaze melt.
Follow all the usual precautions with turning off the electric kiln at the
switches AND the circuit box before reaching into the hot electric kiln! I
didn't have any problems after doing that....the preheat in the electric
kiln could also approach glaze melt (cone 06) with the process.....of
course you have to move hot ware a bit farther, but I got ALL of those
rascals Raku fired without structural cracking. Hope this helps?
Ron in Kansas City.
| |
|
