vince pitelka on sat 5 may 01
> 1. Have you done it?
> 2. Due to the slower electric firing than gas, will blackness occur or
> will deposited carbon eventually dissipate?
> 3. Will any escaping smoke (carbon) affect the kiln elements
> 4. Any other thoughts??
Kurt -
You can get jet-black with a tightly sealed sagger fired at very low
temperature - no more than 700 or 800 degrees F. A well-sealed
aluminum-foil sagger works good for this. If you go this route, use
heavy-duty aluminum foil, fill with sawdust, and fold/crimp all the seams.
A better way to get blackware without doing a proper blackware bonfiring is
to use a raku kiln. Heat the wares up to about cone 018 in the raku kiln,
take the wares out with tongs, group them in a bed of sawdust in a trash
can, cover with more sawdust, and seal the can tightly. Or even better,
group them on a bed of sawdust out in the open, completely cover the wares
with more sawdust, and then bury in sand, dirt, or ashes. Grouping the
wares concentrates more heat to volatize the sawdust, producing more carbon.
In order for this to give a saturated black the wares must be coated with
terra sig. In my experience a OM-4 ball clay sig works best to get
jet-black.
Good luck, and let me know how it turns out.
- 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/
Kurt Wild on sat 5 may 01
I have been asked about doing blackware firing (up to 1400 degrees F.) i=
n
a saggar in an electric kiln but don't have all the answers.
Anyone out there able to answer the following:
1. Have you done it?
2. Due to the slower electric firing than gas, will blackness occur or
will deposited carbon eventually dissipate?
3. Will any escaping smoke (carbon) affect the kiln elements
4. Any other thoughts??
Kurt
e-mail:
Web site: http://wwwpp.uwrf.edu/~kw77
Current work: http://wwwpp.uwrf.edu/~kw77/Available.html
Studio: http://wwwpp.uwrf.edu/~kw77/Odd.html
Dannon Rhudy on sat 5 may 01
>
>1. Have you done it?
>2. Due to the slower electric firing than gas, will blackness occur or
>will deposited carbon eventually dissipate?
>3. Will any escaping smoke (carbon) affect the kiln elements
>4. Any other thoughts??
I've done this, Kurt. You do not need to reach 1400F to make
blackware. Depending on what is in the saggar to make the
carbon, 800F - 1000F is hot enough. The pots will stay black
at those temps. Seal the saggar well. If the saggar is well
sealed, not much will escape to interfere with the elements.
I believe that Russell Fouts fires this way all the time, by the
way.
regards
Dannon Rhudy
Russel Fouts on sun 6 may 01
Kurt,
>> I have been asked about doing blackware firing (up to 1400 degrees F.) in a saggar in an electric kiln but don't have all the answers. <<
Stay below 1173f/650c/^020 if you want to use an aluminum foil sagger
(easiest, most air tight)
>> 1. Have you done it? <<
All the time. Black is EASY! (too easy, really)
>> 2. Due to the slower electric firing than gas, will blackness occur or will deposited carbon eventually dissipate? >>
You can fire as slow or as fast as you like, the longer the piece is in
the smoke the more black you get. This depends also on the amount of
combustible (newspaper in my case) you use and the "receptivity" of the
body, or sig.
>> 3. Will any escaping smoke (carbon) affect the kiln elements <<
Nope! bur keep in mind that, with this method, you'll need a lot less
paper than you think. Do vent though to protect yourself and your lungs.
>> 4. Any other thoughts?? <<
Go for it!
Russel
Russel Fouts
Mes Potes et Mes Pots
Brussels, Belgium
Tel: +32 2 223 02 75
Fax: +32 2 210 04 06
Mobile: +32 476 55 38 75
Web: www.mypots.com
Snail Scott on sun 6 may 01
At 11:01 PM 5/5/01 -0500, you wrote:
>Kurt -
>You can get jet-black with a tightly sealed sagger fired at very low
>temperature - no more than 700 or 800 degrees F...
>A better way to get blackware without doing a proper blackware bonfiring is
>to use a raku kiln... In my experience a OM-4 ball clay sig works best to
get
>jet-black...
>- Vince
You could skip the kiln entirely!
Put the work on a 'tripod' of shards,
put a dried flowerpot over the work,
put cowshit inside and out, and light
the sucker! Deep solid blacks without
terra sig, and without much effort.
Takes an hour or two.
-Snail
MOLINA, RAFAEL on thu 17 may 01
Vince and others on the List:
I have seen your work at McDowell's website and in a recent issue of CM
(photo accompanying the Behrens' piece). I concede that you have vast
experience in the pit-fire/sagger-fire process, but the following statement
seems too narrow and dogmatic.
"In order for this to give a saturated black the wares must be coated with
terra sig. In my experience a OM-4 ball clay sig works best to get
jet-black."
Perhaps, with the processes you describe, which are a fairly common ways of
working, a terra sig is necessary but I have to question it.
As you know, a terra sig is used for both color and texture. The particle
size of the materials, and the technique for polishing (rubbing the clay
with plastic, dry chamois, etc.,...)affect the texture which can range from
a satin to a gloss finish. The firing temperature is also a factor with
regard to surface texture. If the ware is fired too high all the labor
involved in producing the surface texture will be for naught.
Color development (i.e. black, saturated, jet, or other) is another area I
disagree with your post. An OM-4 ball clay without the presence of an added
colorant (Some form of Iron is best. Yes, I know as a secondary clay OM-4
contains impurities including perhaps small amounts of Iron) may indeed turn
black, but not as black as an iron bearing terra sig or slip or claybody.
From my many years of experience sagger-firing, I believe it is the presence
of iron in a decorating media (terra sig or slip) or a claybody fired in a
reducing atmosphere that is responsible for the relative blackness of an
object. Sure if a lighter colored material comes in direct contact with
organic material such a sawdust it will be somewhat black, but that is a
result of something other than an Element responding to a firing atmosphere.
I know this empirically as I have sagger-fired a broad range of sigs, slips,
and bodies. An iron-bearing material produces the deepest darkest black.
One of the best videos I show my students which demonstrates pots decorated
with an iron-bearing slip and bon-fired to produce the most beautiful blacks
is "Maria: The Indian Potter of San Ildefonso." Clearly, they chose the
iron-bearing slip applied prior to burnishing and the iron-bearing slip for
decorating over the burnished pot with a Yucca leaf for a reason.
Ciao,
Rafael
In Arlington where I just completed the Motorcycle Traing Course and
received a 10% discount on my insurance and a $ 50 gift certificate from
H.O.G.
Rafael Molina, MFA
Assistant Professor of Art
Department of Music, Art, and Dance
Tarrant County College-Southeast Campus
2100 Southeast Parkway
Arlington, TX 76018-3144
(817) 515-3711
(817) 515-3189 fax
-----Original Message-----
From: vince pitelka [mailto:vpitelka@DTCCOM.NET]
Sent: Saturday, May 05, 2001 11:01 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Electric blackware/saggar firing?
> 1. Have you done it?
> 2. Due to the slower electric firing than gas, will blackness occur or
> will deposited carbon eventually dissipate?
> 3. Will any escaping smoke (carbon) affect the kiln elements
> 4. Any other thoughts??
Kurt -
You can get jet-black with a tightly sealed sagger fired at very low
temperature - no more than 700 or 800 degrees F. A well-sealed
aluminum-foil sagger works good for this. If you go this route, use
heavy-duty aluminum foil, fill with sawdust, and fold/crimp all the seams.
A better way to get blackware without doing a proper blackware bonfiring is
to use a raku kiln. Heat the wares up to about cone 018 in the raku kiln,
take the wares out with tongs, group them in a bed of sawdust in a trash
can, cover with more sawdust, and seal the can tightly. Or even better,
group them on a bed of sawdust out in the open, completely cover the wares
with more sawdust, and then bury in sand, dirt, or ashes. Grouping the
wares concentrates more heat to volatize the sawdust, producing more carbon.
In order for this to give a saturated black the wares must be coated with
terra sig. In my experience a OM-4 ball clay sig works best to get
jet-black.
Good luck, and let me know how it turns out.
- 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
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settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at
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Susan Fox-Hirschmann on fri 18 may 01
Dear Vince,
I am curious to know if this is the method you will be using at your
workshop at "your" crafts center in early june?
Susan
(delighted to be taking that very workshop!)
>From: vince pitelka
>Reply-To: Ceramic Arts Discussion List
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Re: Electric blackware/saggar firing?
>Date: Fri, 18 May 2001 00:18:00 -0500
>
> > I have seen your work at McDowell's website and in a recent issue of CM
> > (photo accompanying the Behrens' piece). I concede that you have vast
> > experience in the pit-fire/sagger-fire process, but the following
>statement
> > seems too narrow and dogmatic.
>
>Sorry Raphael, but in a traditional blackware firing, which is what I do, a
>ball clay terra sig gives the blackest black - much blacker than a redart
>sig. The reason for this is that the ball clay sig is actually more
>porous,
>because a ball clay starts out with much finer particle size, and it is
>impossible to settle out the ball clay suspension as occurs with the redart
>suspension. So you get a much finer sig with redart than with ball clay -
>it is denser, and accepts less carbon. So the ball clay sig, which still
>polishes beautifully, is more porous, and accepts the carbon. In a true
>blackware firing it is carbon that creates the black color, and iron has
>absolutely nothing to do with it. And a pot which is uncoated or painted
>with an ordinary slip and is not burnished or polished and fired in a
>blackware firing only gives a charcoal gray. It will never give a
>jet-black.
>
>When I referred to getting blackware in saggers, I specifically referred to
>very low temperature sagger firing, which produces black because of similar
>physical phenomenon as occurs in a smothered blackware firing, such as
>Maria
>and Julian use - high concentrations of trapped smoke impacting the porous
>surface of the clay. Higher temperature sagger firings are a completely
>different process.
>
>Maria and Julian used a red clay burnishing slip, but it was not refined
>like a terra sig. So even though the surface was very finely polished, it
>was still porous on a microscopic level, and accepted more carbon than a
>redart sig will take, giving a very rich black finish.
>
>I appreciate your experiences and knowledge, but the situations you cite
>have little connection to the processes I use.
>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.
_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com
vince pitelka on fri 18 may 01
> But, when painting designs on a burnished
> surface with slip (left unburnished for
> contrast) it comes out the same color as
> the clay underneath; no terra sig involved.
> Black-on-black. The matte surface looks
> slightly less black, I believe, only because
> it is a matte surface, and catches the light
> differently. It's not grey, though.
Snail -
I would call it a charcoal gray.
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/
vince pitelka on fri 18 may 01
> I have seen your work at McDowell's website and in a recent issue of CM
> (photo accompanying the Behrens' piece). I concede that you have vast
> experience in the pit-fire/sagger-fire process, but the following
statement
> seems too narrow and dogmatic.
Sorry Raphael, but in a traditional blackware firing, which is what I do, a
ball clay terra sig gives the blackest black - much blacker than a redart
sig. The reason for this is that the ball clay sig is actually more porous,
because a ball clay starts out with much finer particle size, and it is
impossible to settle out the ball clay suspension as occurs with the redart
suspension. So you get a much finer sig with redart than with ball clay -
it is denser, and accepts less carbon. So the ball clay sig, which still
polishes beautifully, is more porous, and accepts the carbon. In a true
blackware firing it is carbon that creates the black color, and iron has
absolutely nothing to do with it. And a pot which is uncoated or painted
with an ordinary slip and is not burnished or polished and fired in a
blackware firing only gives a charcoal gray. It will never give a
jet-black.
When I referred to getting blackware in saggers, I specifically referred to
very low temperature sagger firing, which produces black because of similar
physical phenomenon as occurs in a smothered blackware firing, such as Maria
and Julian use - high concentrations of trapped smoke impacting the porous
surface of the clay. Higher temperature sagger firings are a completely
different process.
Maria and Julian used a red clay burnishing slip, but it was not refined
like a terra sig. So even though the surface was very finely polished, it
was still porous on a microscopic level, and accepted more carbon than a
redart sig will take, giving a very rich black finish.
I appreciate your experiences and knowledge, but the situations you cite
have little connection to the processes I use.
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/
Snail Scott on fri 18 may 01
At 12:18 AM 5/18/01 -0500, you wrote:
And a pot which is uncoated or painted
>with an ordinary slip and is not burnished or polished and fired in a
>blackware firing only gives a charcoal gray. It will never give a
>jet-black.
>- Vince
But, when painting designs on a burnished
surface with slip (left unburnished for
contrast) it comes out the same color as
the clay underneath; no terra sig involved.
Black-on-black. The matte surface looks
slightly less black, I believe, only because
it is a matte surface, and catches the light
differently. It's not grey, though.
-Snail
vince pitelka on sat 19 may 01
> Isn't a "porous sig" an oxymoron. After all, terra sigillata is Latin for
> sealed earth.
Raphael -
This is a little silly. Of course it is not an oxymoron. The sig is much
more sealed than a plain claybody, but it is still plenty porous, depending
on the particular sig and the way it is applied and polished.
> It's true that in some cases the carbon penetrates the porous body and
gives
> color/value which you can verify by looking at the cross section of a
broken
> shard of a lighter colored clay. However, that color/value has only
> slightly penetrated the wall of the piece. If you compare that with a
shard
> of an iron bearing clay you see that the color/value is present throughout
> the thickness of the wall which in my opinion is the result of a metal
oxide
> in the claybody responding to a reducing atmosphere. In addition to a
> difference in the depth of the color/value physically, I believe there is
a
> difference visually.
While it may be possible for an iron bearing claybody to be darker
throughout its thickness after a blackware firing, this has little to do
with the surface color in a blackware-fired piece. That is all the result
of carbon impaction.
> While it's true that there is a distinct difference between low fire
(below
> ^010) and high fire sagger (stoneware temps), I'm skeptical of a
difference
> between "very low temperature sagger firing" and "smothered blackware
> firing." I speculate that the range is narrow between the temperatures
> achieved in a below ground pit or an above ground bonfire. Of course, the
> only way to know would be to use a series of measuring tools including
> pyrometric cones, a pyrometer, and claybody shrinkage and porosity test
> bars. Popovi Da in the video "Maria: The Indian Potter of San Idefonso"
> suggests the temps in their firing of around 1300-1400 F.
I never said there was a difference between very low temperature sagger
firing and blackware firing. In fact I said that the phenomenon was
essentially the same in both - intense carbon impaction. Pitfiring can
reach significantly higher temperatures, as the coals settle down among the
wares - that is why there is much more thermochemical activity in a
pitfiring - similar to a low-fire or low-midrange sagger firing.
> I believe what we are debating here is the relative blackness of an
object.
> If you compare and contrast the rich value of the surface of an iron
bearing
> clay with or without an iron bearing slip applied over and reduction-fired
> such as a Maria pot or a Juan Quezada pot or a Michael Wisner pot and an
> object which has a terra sig applied and pit or bonfired you would see an
> obvious difference.
No you would not, Raphael, and you need to phrase these things more
carefully, because your tone is condescending. I have produced blackware
pots with ball clay terra sig which came out as jet-black as any pot you
have ever seen anywhere.
> Finally, a word about terra sig's for primitive fired work. I respect an
> artist's right to make aesthetic choices for their artwork, but it just
> seems to me to add to the work when using a sig and primitive firing. Why
> spend the time and labor finding a sig that will fit your body and not
flake
> off, preparing the sig and then applying to a piece when you can just
> burnish an iron-bearing claybody and achieve a similar or closely related
> result.
I do not care to spar with you about this, but it is apparent that you do
not have much experience with terra sig. It is not at all difficult to make
an appropriate sig that does not flake at all, and all in all the
application and polishing is MUCH EASIER than burnishing.
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/
MOLINA, RAFAEL on sat 19 may 01
Vince:
I have a few more questions.
>So the ball clay sig, which still polishes beautifully, is more porous,
Isn't a "porous sig" an oxymoron. After all, terra sigillata is Latin for
sealed earth.
>In a true blackware firing it is carbon that creates the black color
It's true that in some cases the carbon penetrates the porous body and gives
color/value which you can verify by looking at the cross section of a broken
shard of a lighter colored clay. However, that color/value has only
slightly penetrated the wall of the piece. If you compare that with a shard
of an iron bearing clay you see that the color/value is present throughout
the thickness of the wall which in my opinion is the result of a metal oxide
in the claybody responding to a reducing atmosphere. In addition to a
difference in the depth of the color/value physically, I believe there is a
difference visually.
>I specifically referred to very low temperature sagger firing, which
produces black because of
>similar physical phenomenon as occurs in a smothered blackware firing, such
as Maria and Julian
>use - high concentrations of trapped smoke impacting the porous surface of
the clay. Higher
>temperature sagger firings are a completely different process.
While it's true that there is a distinct difference between low fire (below
^010) and high fire sagger (stoneware temps), I'm skeptical of a difference
between "very low temperature sagger firing" and "smothered blackware
firing." I speculate that the range is narrow between the temperatures
achieved in a below ground pit or an above ground bonfire. Of course, the
only way to know would be to use a series of measuring tools including
pyrometric cones, a pyrometer, and claybody shrinkage and porosity test
bars. Popovi Da in the video "Maria: The Indian Potter of San Idefonso"
suggests the temps in their firing of around 1300-1400 F.
I believe what we are debating here is the relative blackness of an object.
If you compare and contrast the rich value of the surface of an iron bearing
clay with or without an iron bearing slip applied over and reduction-fired
such as a Maria pot or a Juan Quezada pot or a Michael Wisner pot and an
object which has a terra sig applied and pit or bonfired you would see an
obvious difference. Ultimately, The artist has to decide the color/value
and texture of the surface of their work and find the materials and
processes to acheive it.
Finally, a word about terra sig's for primitive fired work. I respect an
artist's right to make aesthetic choices for their artwork, but it just
seems to me to add to the work when using a sig and primitive firing. Why
spend the time and labor finding a sig that will fit your body and not flake
off, preparing the sig and then applying to a piece when you can just
burnish an iron-bearing claybody and achieve a similar or closely related
result.
Ciao,
Rafael
Rafael Molina, MFA
Assistant Professor of Art
Department of Music, Art, and Dance
Tarrant County College-Southeast Campus
2100 Southeast Parkway
Arlington, TX 76018-3144
(817) 515-3711
(817) 515-3189 fax
-----Original Message-----
From: vince pitelka [mailto:vpitelka@DTCCOM.NET]
Sent: Friday, May 18, 2001 12:18 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Electric blackware/saggar firing?
> I have seen your work at McDowell's website and in a recent issue of CM
> (photo accompanying the Behrens' piece). I concede that you have vast
> experience in the pit-fire/sagger-fire process, but the following
statement
> seems too narrow and dogmatic.
Sorry Raphael, but in a traditional blackware firing, which is what I do, a
ball clay terra sig gives the blackest black - much blacker than a redart
sig. The reason for this is that the ball clay sig is actually more porous,
because a ball clay starts out with much finer particle size, and it is
impossible to settle out the ball clay suspension as occurs with the redart
suspension. So you get a much finer sig with redart than with ball clay -
it is denser, and accepts less carbon. So the ball clay sig, which still
polishes beautifully, is more porous, and accepts the carbon. In a true
blackware firing it is carbon that creates the black color, and iron has
absolutely nothing to do with it. And a pot which is uncoated or painted
with an ordinary slip and is not burnished or polished and fired in a
blackware firing only gives a charcoal gray. It will never give a
jet-black.
When I referred to getting blackware in saggers, I specifically referred to
very low temperature sagger firing, which produces black because of similar
physical phenomenon as occurs in a smothered blackware firing, such as Maria
and Julian use - high concentrations of trapped smoke impacting the porous
surface of the clay. Higher temperature sagger firings are a completely
different process.
Maria and Julian used a red clay burnishing slip, but it was not refined
like a terra sig. So even though the surface was very finely polished, it
was still porous on a microscopic level, and accepted more carbon than a
redart sig will take, giving a very rich black finish.
I appreciate your experiences and knowledge, but the situations you cite
have little connection to the processes I use.
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.
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