Ray and Claudia on tue 23 feb 99
Hi all...
I just unloaded another pit firing and lost 3 out of 6 vessels. I am
not happy with those percentages, and wonder...can we talk!
I am using Warm Springs Red...a typical low fire earthenware, which I
first bisque to ^06. These vessels are burnished, so this is as high as
I dare to bisque. My fuel is a mixture of sawdust, wood pellets, and
various combustibles from around the landscape. When I used Raku clay,
I had very little breakage (but I could not burnish), and I realize that
this red clay is tighter and more prone to disaster than that Raku
clay. Still...I should be able to do better. Should I fire fewer
pieces at one time...I fire 6 usually, three above, three below. The
breaks are not consistent as to position in the kiln, so I do not have
problems with the vessels falling into each other. I have not been
diligent about filling the insides and wonder if this could be part of
the problem. We have been having a lot of wind, but the outside
temperature is not awfully cold here these days...around 50 degrees. I
did not open the kiln until it was totally cold....just to prevent the
cracks! Of course, it was the larger vessels that cracked...which could
also be part of the problem. I just wonder if anyone out there has had
this problem and has minimized it in any way. Thank you!
Claudia
Sylvia See on wed 24 feb 99
I primitive fire in old 18cu.ft. kilns all the time and rarely get cracked
or broken pots, and I have primitive fired everything from lowfire to
highfire clay. The raku clay gives the roughest surface. I like midfire
stoneware, or midfire porcelain but have also primitive fired the highfire
clays with excellent results. I use sawdust obtained from a local furniture
manufacturer, and they are always glad to let me have the sawdust rather
than pay to have it taken away. I use about 6 inches of sawdust on the
bottom, I do fill the pots with sawdust, and I put layer upon layer of pots
with sawdust layer between the pots. I also throw in vermiculate around the
pots, and red or blue salt from local farm supplier, and sprinkle copper
carbonate close and on pots, and I have tossed in some dog food and got some
neat new colors I never had before, including a bright tourquoise. If you
are using terra sig, prepare your pots like always. I fill my kiln to the
top, start the fire from the top, and close the lid when it gets a good
start. By taking out the peep holes and having a very tiny crack in the lid
I find I get enough air to keep this burning slowly for a couple of days.
The pots slowly settle to the bottom, and sit on top of each other and I
can't remember when I had one crack or break. This is alot different than
burning in a barrel full of holes, and using wood. Much slower, but alot
less smoke, and I do this right in town. The fire is contained in the kiln,
so the fire hazard is alot less. I do keep the lid cracked just a hair,
until it gets a good burn going, and I watch it carefully in this stage as
sparks could start a fire. After it gets going though I put bricks on the
lid to keep it from blowing open, and it does its thing by itself. I don't
even wait until it is cold before removing the pots. I envy your patience. I
got this idea from a friend who spent years in Africa where they primitive
fire in the ground for days with a tiny hole in the top of a mud mound, and
a very small trickle of smoke coming out of the hole. The kilns hold the
heat really well, and one of these days I am going to use my pyrometer to
measure just how hot it gets in the fire. Different clays give different
effects. Laguna B-mix gives a bluegrey finish and burnishes beautifully. Mid
fire porcelain usually gives me a lot less color, mainly blacks, but
burnishes beautifully. I;ve had great color variations with stoneware. I
brush a solution of bluestone and water on my pieces before firing, instead
of terra sig. The ones I did with terra sig, were beautiful but black. I
also wrap flowers and leaves around the pots and wrap them in white tissue
paper before placing them in sawdust for fossil effects and shadows. I have
also mixed scraps of the clay I am throwing with mason stains and mixed to a
brushing consistency, coating the pots in the leather hard stage with
colored slip and then burnished them. They give a nice colored primitive
effect.
If you want to continue using wood and sawdust for a faster firing, you
might want to try layers of old chicken wire between you layers to buffer
the pots falling on top of each other.
Have fun!
Sylvia See Claresholm, Alberta sylviac@telusplanet.net
-----Original Message-----
From: Ray and Claudia
To: CLAYART@LSV.UKY.EDU
Date: Tuesday, February 23, 1999 5:41 AM
Subject: pit fires and cracks
>----------------------------Original message----------------------------
>Hi all...
>I just unloaded another pit firing and lost 3 out of 6 vessels. I am
>not happy with those percentages, and wonder...can we talk!
>I am using Warm Springs Red...a typical low fire earthenware, which I
>first bisque to ^06. These vessels are burnished, so this is as high as
>I dare to bisque. My fuel is a mixture of sawdust, wood pellets, and
>various combustibles from around the landscape. When I used Raku clay,
>I had very little breakage (but I could not burnish), and I realize that
>this red clay is tighter and more prone to disaster than that Raku
>clay. Still...I should be able to do better. Should I fire fewer
>pieces at one time...I fire 6 usually, three above, three below. The
>breaks are not consistent as to position in the kiln, so I do not have
>problems with the vessels falling into each other. I have not been
>diligent about filling the insides and wonder if this could be part of
>the problem. We have been having a lot of wind, but the outside
>temperature is not awfully cold here these days...around 50 degrees. I
>did not open the kiln until it was totally cold....just to prevent the
>cracks! Of course, it was the larger vessels that cracked...which could
>also be part of the problem. I just wonder if anyone out there has had
>this problem and has minimized it in any way. Thank you!
>Claudia
>
douglas gray on wed 24 feb 99
In message Ray and Claudia writes:
> ----------------------------Original message----------------------------
> Hi all...
> I just unloaded another pit firing and lost 3 out of 6 vessels. I am
> not happy with those percentages, and wonder...can we talk!
Have you tried adding some sand to your clay body. It helps to temper the clay
and keep it more open. You should still be able to burnish the surface.
Also might try putting your to-be-fired pots in the shards of your broken
already-been-fired pots. This will shelter them some from the dirrect flame.
doug
============================================================================ =)
Douglas E. Gray, Assistant Professor of Art
P.O. Box 100547
Department of Fine Arts and Mass Communication
Francis Marion University
Florence, South Carolina 29501-0547
dgray@fmarion.edu
843/661-1535
Vince Pitelka on wed 24 feb 99
>I just unloaded another pit firing and lost 3 out of 6 vessels. I am
>not happy with those percentages, and wonder...can we talk!
>I am using Warm Springs Red...a typical low fire earthenware, which I
>first bisque to ^06. These vessels are burnished, so this is as high as
>I dare to bisque. My fuel is a mixture of sawdust, wood pellets, and
>various combustibles from around the landscape. When I used Raku clay,
>I had very little breakage (but I could not burnish), and I realize that
>this red clay is tighter and more prone to disaster than that Raku
>clay.
Claudia -
Some claybodies are not very appropriate for the uneven heat in a sawdust
smoking or a pitfire. Sounds like your claybody might be one of these. But
you say you cannot burnish your raku body. Whay is that? Why not use the
raku body, and then apply a slip that you can burnish, such as a terra sig?
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Andrew Buck on wed 24 feb 99
Claudia,
You could make the pots out of the raku clay then cover them with a slip
made from the red clay before burnishing. Best of both worlds?
Andy Buck
Raincreek Pottery
Port Orchard, Washington
On Tue, 23 Feb 1999, Ray and Claudia wrote:
> ----------------------------Original message----------------------------
> Hi all...
> I just unloaded another pit firing and lost 3 out of 6 vessels. I am
> not happy with those percentages, and wonder...can we talk!
> I am using Warm Springs Red...a typical low fire earthenware, which I
> first bisque to ^06. These vessels are burnished, so this is as high as
> I dare to bisque. My fuel is a mixture of sawdust, wood pellets, and
> various combustibles from around the landscape. When I used Raku clay,
> I had very little breakage (but I could not burnish), and I realize that
> this red clay is tighter and more prone to disaster than that Raku
> clay. Still...I should be able to do better. Should I fire fewer
> pieces at one time...I fire 6 usually, three above, three below. The
> breaks are not consistent as to position in the kiln, so I do not have
> problems with the vessels falling into each other. I have not been
> diligent about filling the insides and wonder if this could be part of
> the problem. We have been having a lot of wind, but the outside
> temperature is not awfully cold here these days...around 50 degrees. I
> did not open the kiln until it was totally cold....just to prevent the
> cracks! Of course, it was the larger vessels that cracked...which could
> also be part of the problem. I just wonder if anyone out there has had
> this problem and has minimized it in any way. Thank you!
> Claudia
>
matthew lettington on fri 26 feb 99
------------------
Are you implying that terra sig is a slip? I'm pretty sure that it is not,
or at least it is not used in the same sense as slip. terra sig is
traditionaly aplied in a thin layer so thin that absolutly no detail is
lost, and then using terra sig in the method you have suggested.
-----Original Message-----
From: Vince Pitelka =3Cvpitelka=40Dekalb.Net=3E
To: CLAYART=40LSV.UKY.EDU =3CCLAYART=40LSV.UKY.EDU=3E
Date: 1999=B3=E2 2=BF=F9 25=C0=CF =B8=F1=BF=E4=C0=CF =BF=C0=C0=FC 10:27
Subject: Re: pit fires and cracks
----------------------------Original message----------------------------
=3EI just unloaded another pit firing and lost 3 out of 6 vessels. I am
=3Enot happy with those percentages, and wonder...can we talk=21
=3EI am using Warm Springs Red...a typical low fire earthenware, which I
=3Efirst bisque to =5E06. These vessels are burnished, so this is as high =
as
=3EI dare to bisque. My fuel is a mixture of sawdust, wood pellets, and
=3Evarious combustibles from around the landscape. When I used Raku clay,
=3EI had very little breakage (but I could not burnish), and I realize that
=3Ethis red clay is tighter and more prone to disaster than that Raku
=3Eclay.
Claudia -
Some claybodies are not very appropriate for the uneven heat in a sawdust
smoking or a pitfire. Sounds like your claybody might be one of these. But
you say you cannot burnish your raku body. Whay is that? Why not use the
raku body, and then apply a slip that you can burnish, such as a terra sig?
- Vince
Vince Pitelka - vpitelka=40DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
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