John Kudlacek on sat 24 apr 04
Occassionally I use a high gloss black glaze on the interior of
stoneware pieces. I would like this glaze to be unblemished by iron spots
coming from the stoneware body. It appears that the major source of such
spots come from fire clay. I have found that using a white engobe over
these surfaces discourages the spotting but on many pieces applying slip
on the interior is impractical if not impossible. (Using a white body is
not the answer as the darker stoneware body is necessary for the color
affects I want on the exterior of the pots.) Any suggestions out there? I
am willing to try a totally new stoneware body. I fire cone 10 reduction.
Thanks,
John
Topeka, KS.
Vince Pitelka on sun 25 apr 04
> If you apply an opaque glaze, like eggshell white, and then put the black
on
> over it, the eggshell is impervious to the iron spots
I'm sorry, but this is misleading advice. The white glaze will blend with
the black glaze and change it considerably. The advice in other posts to
put a dark slip under the black glaze is excellent. But from my own point
of view, I'd love to see those iron blooms peeking out all over the black
glaze. I just can't imagine anything wrong with that. But that's my point
of view, which doesn't necessarily have anything to do with what John
Kudlacek is seeking.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Ivor and Olive Lewis on sun 25 apr 04
Dear John,
Other than changing clay perhaps a thick wash of black slip interposed
between the body and your glaze might be effective.
Best regards,
Ivor Lewis. Redhill, South Australia
Lee Love on sun 25 apr 04
John Kudlacek wrote:
>on the interior is impractical if not impossible. (Using a white body is
>not the answer as the darker stoneware body is necessary for the color
>affects I want on the exterior of the pots.) Any suggestions out there? I
>am willing to try a totally new stoneware body. I fire cone 10 reduction.
>
>
Have you thought about using a dark slip on the outside of a light
body? At my teacher's workshop, the light colored Mashiko Nami
Tsuchi was coated on the inside and outside by dipping with ocher
clay. When I use the nami clay, I typically brush an ocher slip on
the inside and then do a hakame white over that, and then I do ocher
inlay on the outside.
With my mugs that are not footed but only cut with a wire, I
inlay an iron bearing clay (made of the same clay as my teacher's iron
clay) in the wire cut and then scrape it. This serves two purposes:
it gives the wire cut more contrast and also makes the bottom
smooth. I usually iron slip up the bottom, so the part not glazed is
warm.
--
Lee in Mashiko, Japan http://mashiko.org
wayneinkeywest on sun 25 apr 04
John:
Maybe I misunderstand you, but wouldn't it be simpler to use
a body that has little or no iron in it, like porcelain? You could
still apply the black slip wherever you wanted, but the iron
spotting problem would be mostly gone, unless it's in the slip.
Wayne Seidl
Key West, Florida, USA
North America, Terra
Latitude 81.8, Longitude 24.4
Elevation 3.1 feet (1m)
----- Original Message -----
From: "John Kudlacek"
> Occassionally I use a high gloss black glaze on the interior of
> stoneware pieces. I would like this glaze to be unblemished by
iron spots
> coming from the stoneware body. It appears that the major source
of such
> spots come from fire clay. I have found that using a white engobe
over
> these surfaces discourages the spotting but on many pieces
applying slip
> on the interior is impractical if not impossible. (Using a white
body is
> not the answer as the darker stoneware body is necessary for the
color
> affects I want on the exterior of the pots.) Any suggestions out
there? I
> am willing to try a totally new stoneware body. I fire cone 10
reduction.
> Thanks,
> John
logan johnson on sun 25 apr 04
Hi John,
have you thought of using the white body for the work then applying the darker stoneware as a slip to the outside? Basicly just the opposite of what you were doing wih the inside.
alot of work but it might give you what your looking for.
Good Luck!
Logan J.
John Kudlacek wrote:
Occassionally I use a high gloss black glaze on the interior of
stoneware pieces. I would like this glaze to be unblemished by iron spots
coming from the stoneware body. It appears that the major source of such
spots come from fire clay. I have found that using a white engobe over
these surfaces discourages the spotting but on many pieces applying slip
on the interior is impractical if not impossible. (Using a white body is
not the answer as the darker stoneware body is necessary for the color
affects I want on the exterior of the pots.) Any suggestions out there? I
am willing to try a totally new stoneware body. I fire cone 10 reduction.
Thanks,
John
Topeka, KS.
______________________________________________________________________________
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Logan Johnson Audeo Studios
www.audeostudios.com
"Carpe Argillam!!"
John Kudlacek on sun 25 apr 04
Hi Wayne, Thanks for your input. The problem with porcelain, which I
also use, is the whiteness of the body interferes with the color of the
glazes on the exterior. For example, what might appear black on stoneware
may come out blue on porcelain.
John
John Kudlacek on sun 25 apr 04
Hi Logan, Thanks for your input. It did cross my mind--applying a dark
slip on the outside--but I am looking for an easy (lazy) way out, like
what clay I may be using that is responsible for iron spots.
John
Donald G. Goldsobel on sun 25 apr 04
If you apply an opaque glaze, like eggshell white, and then put the black on
over it, the eggshell is impervious to the iron spots
Donald
----- Original Message -----
From: "John Kudlacek"
To:
Sent: Saturday, April 24, 2004 8:49 PM
Subject: Iron Spots in Stoneware
> Occassionally I use a high gloss black glaze on the interior of
> stoneware pieces. I would like this glaze to be unblemished by iron spots
> coming from the stoneware body. It appears that the major source of such
> spots come from fire clay. I have found that using a white engobe over
> these surfaces discourages the spotting but on many pieces applying slip
> on the interior is impractical if not impossible. (Using a white body is
> not the answer as the darker stoneware body is necessary for the color
> affects I want on the exterior of the pots.) Any suggestions out there? I
> am willing to try a totally new stoneware body. I fire cone 10 reduction.
> Thanks,
> John
> Topeka, KS.
>
>
____________________________________________________________________________
__
> 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.
Donald G. Goldsobel on mon 26 apr 04
Eggshell is a stony matt and it does not blend with the over glaze.
Donald
----- Original Message -----
From: "Vince Pitelka"
To:
Sent: Sunday, April 25, 2004 8:11 PM
Subject: Re: Iron Spots in Stoneware
> > If you apply an opaque glaze, like eggshell white, and then put the
black
> on
> > over it, the eggshell is impervious to the iron spots
>
> I'm sorry, but this is misleading advice. The white glaze will blend with
> the black glaze and change it considerably. The advice in other posts to
> put a dark slip under the black glaze is excellent. But from my own point
> of view, I'd love to see those iron blooms peeking out all over the black
> glaze. I just can't imagine anything wrong with that. But that's my
point
> of view, which doesn't necessarily have anything to do with what John
> Kudlacek is seeking.
> Best wishes -
> - Vince
>
> Vince Pitelka
> Appalachian Center for Craft, Tennessee Technological University
> Smithville TN 37166, 615/597-6801 x111
> vpitelka@dtccom.net, wpitelka@tntech.edu
> http://iweb.tntech.edu/wpitelka/
> http://www.tntech.edu/craftcenter/
>
>
____________________________________________________________________________
__
> 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.
David Beumee on mon 26 apr 04
Here's a cone 10 stoneware body that will not bleed iron spots through your black glaze, or even a white glaze.
SS1,18B,Rev.#3, cone 10 stoneware throwing body, David Beumee
25 Champion ball clay
25 New Foundry Hill Creme
17 35 mesh Hawthorn Bond fire clay
18 50 mesh Hawthorn Bond fire clay
10 G-200 feldspar
5 200 mesh silica
If you want a smoother texture to the body, substitute all 50 mesh Hawthorn Bond.
For a coarser body, use all 35 mesh Hawthorn.
Excellent workability
16% shrinkage @ cone 10 (wet mixed)
0.4% absorption @cone 10
No cracking or warping
Medium tooth
Mottled light Grey fired color in reduction
Fits Jim Robinson's Glaze Test Series (GTS) 2-10 (Excellent glaze fit)
David Beumee
Earth Alchemy Pottery
Lafayette, CO
Let me know how you like it.
> Occassionally I use a high gloss black glaze on the interior of
> stoneware pieces. I would like this glaze to be unblemished by iron spots
> coming from the stoneware body. It appears that the major source of such
> spots come from fire clay. I have found that using a white engobe over
> these surfaces discourages the spotting but on many pieces applying slip
> on the interior is impractical if not impossible. (Using a white body is
> not the answer as the darker stoneware body is necessary for the color
> affects I want on the exterior of the pots.) Any suggestions out there? I
> am willing to try a totally new stoneware body. I fire cone 10 reduction.
> Thanks,
> John
> Topeka, KS.
>
> ______________________________________________________________________________
> 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.
Lee Love on tue 27 apr 04
David Beumee wrote:
>Here's a cone 10 stoneware body that will not bleed iron spots through your black glaze, or even a white glaze.
>
>
>
But David, he wanted the iron in the body for the color of the glazes
on the exterior of the pot. :-)
--
in Mashiko, Japan http://mashiko.org
Tracy Wilson on wed 28 apr 04
I had a customer that wanted no iron spots blooming through a deep cobalt
glaze. That glaze is simliar in oxidation and reduction so her set of
dishes was fired in a strict oxidation atmosphere. (I'm fortunate to have
both gas and electric kilns)
Another thing I've done (you could try this on a porcelain body) is to mix
up Cynthia Bringle's slip in the Penland book and mix oxides for black.
Mix it thin and dip the pieces in quickly. This will give you a thin wash
that has darkened the iron free clay body uniformly. I use this method in
reverse (Penland slip with zircopax)because I use a dark clay body but
sometimes want the white background for certain glazes.
Good Luck,
Tracy Wilson
Saltbox Pottery
4 Shaw Rd.
Woolwich, ME 04579
1-800-755-7687
www.saltboxpottery.com
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