vince pitelka on sat 27 oct 01
> I also had a question about peoples pit firings. How can it be called a
pit
> firing if it isn't in a pit??? I don't need an answer or discussion on
that
> one. Just an observation.
Lisa -
Well you're gonna get an answer anyway. It is true that the term "pit
firing" is used in a rather careless way. I don't care if the wares are
really in a pit, but a pit firing is a variation on the bonfiring process,
and in order to call it a pit firing it needs to get up at least close to
low-fire temperatures. So a smoldering sawdust firing should not be called
a pit firing, whether it is in a pit or a can or a brick enclosure. And of
course the sawdust smoldering process is not a true firing, because it does
not reach even minimal sintering temperatures. Surface effects from a
smoldering sawdust firing often need to be fixed with a varnish, wax, or
other sealant.
To do a real pit firing, the wares are normally bedded in a pit, a can, or a
brick enclosure along with with sawdust, wood shavings, and/or small pieces
of wood, and a good-sized bonfire is carefully built on top. Once the
bonfire burns down the coals slowly burn through the sawdust and wood
directly around the wares. This usually takes eight or ten hours to
complete, and at least that long to cool. The surface effects are entirely
different from a smoldering sawdust firing.
In the basic true pitfiring process there is rarely any black color, because
the temperatures are too hot for retention of carbon. When some carbon
black is desired, it is possible to introduce more sawdust as the firing
starts to cool.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Jeff Tsai on sun 28 oct 01
Names are arbitrary in English. Pit firing? The word pit itself has many
meanings beyond just a hole in the ground.
I mean, why do we call a bisque firing in an electric kiln a firing? there is
no fire involved, only heated coils of metal. Should we thus distinguish
between the difference of a bisque firing in a gaskiln and a bisque coil
warming in an electric?
-jeff
John Baymore on mon 29 oct 01
I mean, why do we call a bisque firing in an electric kiln a firing? ther=
e
is
no fire involved, only heated coils of metal. Should we thus distinguish
between the difference of a bisque firing in a gaskiln and a bisque coil
warming in an electric?
If heating ceramics in a kiln where there is burning fuel is called
"firing".......
..........maybe heating ceramics in an electric kiln should be called
"electric-ing" ?
There is already a word for doing that to other stuff. "Hey, I gotta' go=
toast a bisque load". .
Best,
..............................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752 (s)
800-900-1110 (s)
JohnBaymore.com
JBaymore@compuserve.com
John.Baymore@GSD-CO.com
"Earth, Water, and Fire Noborigama Woodfiring Workshop 2002 Dates TBA"
Deborah Britt on mon 29 oct 01
On Sat, 27 Oct 2001 18:50:51 -0500, vince pitelka
wrote:
Surface effects from a
>smoldering sawdust firing often need to be fixed with a varnish, wax, or
>other sealant.
>
Hi, Vince and everyone:
I just finished a sawdust firing, and got some nice carbon effects.
However, I did get a crack, and the oxidized areas on the orange clay body
look kind of raw. This is a 2 foot in diameter sculptural platter. I was
thinking of reinforcing the crack with black PC7 glue and let it ride, but
if I do, it will be an even starker contrast with the orange areas.
Is there a way to permanently stain the natural variations in the texture of
the piece to quiet it down without re-firing? I thought varnish or wax
might make to too shiny.
Any ideas would be greatly appreciated.
Deborah Britt
>
>___________________________________________________________________________
___
>Send postings to clayart@lsv.ceramics.org
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Naomi Rieder on mon 29 oct 01
Vince,
In your post describing a "real" pit firing, you wrote that there is rarely
any black color in a basic true pitfire because the temperatures are too hot
for retention of carbon. The firings I've been doing, in a surface pit made
from high-fire brick, with the set-up as you describe: sawdust on the bottom
(4"-5"), pots, kindling, wood piled up to the top (about 2' or so), the
pots--from a 50/50 ball clay & talc body, with terra sigs--have not only
retained beautiful carbon markings, but the pots appear to have
vitrified--they ring like a bell when pinged. Could this carbon retention &
pinging be happening because the pots are very thin? I don't add anything
once the fire starts, just cover the top of the "pit" with corrugated steel
sheets.
Sincerely,
Naomi Rieder
Carolyn Bronowski on mon 29 oct 01
Interesting, Vince, thanks. I've done "regular sawdust" fire, get the
black. I've done pit fire, with sawdust in the bottom, chemicals, pots,
manure then brush. Some color, alot of black. Sooooo-I'm going out to my
friend's orchard --he'll dig the pit with his scoop, then I'll just put the
pots/sculptures in and cover with wood and burn. My pots/sculptures
are IMCO sculpture mix 412 with white terrasig sprayed on, bisque to ^012.
I had planned to sprinkle rock salt and some chemicals, but now I'm
rethinking that option after your post. Thanks Carolyn
> -----Original Message-----
> From: vince pitelka [SMTP:vpitelka@DTCCOM.NET]
> Sent: Saturday, October 27, 2001 4:51 PM
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Re: defining pit firing
>
> > I also had a question about peoples pit firings. How can it be called a
> pit
> > firing if it isn't in a pit??? I don't need an answer or discussion on
> that
> > one. Just an observation.
>
> Lisa -
> Well you're gonna get an answer anyway. It is true that the term "pit
> firing" is used in a rather careless way. I don't care if the wares are
> really in a pit, but a pit firing is a variation on the bonfiring process,
> and in order to call it a pit firing it needs to get up at least close to
> low-fire temperatures. So a smoldering sawdust firing should not be
> called
> a pit firing, whether it is in a pit or a can or a brick enclosure. And
> of
> course the sawdust smoldering process is not a true firing, because it
> does
> not reach even minimal sintering temperatures. Surface effects from a
> smoldering sawdust firing often need to be fixed with a varnish, wax, or
> other sealant.
>
> To do a real pit firing, the wares are normally bedded in a pit, a can, or
> a
> brick enclosure along with with sawdust, wood shavings, and/or small
> pieces
> of wood, and a good-sized bonfire is carefully built on top. Once the
> bonfire burns down the coals slowly burn through the sawdust and wood
> directly around the wares. This usually takes eight or ten hours to
> complete, and at least that long to cool. The surface effects are
> entirely
> different from a smoldering sawdust firing.
>
> In the basic true pitfiring process there is rarely any black color,
> because
> the temperatures are too hot for retention of carbon. When some carbon
> black is desired, it is possible to introduce more sawdust as the firing
> starts to cool.
> Best wishes -
> - Vince
>
> Vince Pitelka
> Appalachian Center for Crafts
> Tennessee Technological University
> 1560 Craft Center Drive, Smithville TN 37166
> Home - vpitelka@dtccom.net
> 615/597-5376
> Work - wpitelka@tntech.edu
> 615/597-6801 ext. 111, fax 615/597-6803
> http://www.craftcenter.tntech.edu/
>
> __________________________________________________________________________
> ____
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
vince pitelka on mon 29 oct 01
> pots--from a 50/50 ball clay & talc body, with terra sigs--have not only
> retained beautiful carbon markings, but the pots appear to have
> vitrified--they ring like a bell when pinged. Could this carbon retention
&
> pinging be happening because the pots are very thin? I don't add anything
> once the fire starts, just cover the top of the "pit" with corrugated
steel
> sheets.
Naomi -
It is possible that you are getting very densely fired wares in pitfiring
with this body. Normally this claybody is never fired above lowfire
temperatures, and I believe it will bloat and/or slump before it actually
vitrifies, and you may be pushing the limit. It would be interesting to
find out what temperature you are getting in your pitfiring. Just make a
bunch of little crude clay covered boxes that a cone will fit in diagonally,
so its midpoint is suspended in mid-air. Bisque fire the boxes and put a
different cone in each one, and include them in your pit-firing close to the
pots. You will be able to get some idea of the temperature by the degree to
which each cone deforms or melts within its box.
I think the variation in black streaks or marks on the pots has to do with
exposure to oxygen as the wares start to cool. Perhaps in the places where
the wares are most protected by ashes, the carbon does not completely
reoxidize out of the clay as it cools.
Best wishes and good luck -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
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