Dave Finkelnburg on mon 5 jun 00
Jeri,
The simple answer to your questions is yes, yes and yes!
Regarding a Chun, or Jun as it is now spelled, Robert Fournier, in his
"Illustrated Dictionary of Practical Pottery," says a Jun glaze is,
"unaffected by kiln atmosphere except that the body color will show through
to a degree..."
As for what glazes look good in oxidation, you really need to fire some
tests, after considering some simple guidelines. Basically, what you need
to look for to tell if a glaze will be any different in oxidation than
reduction is whether it contains materials which will be reduced by a
reduction firing.
Iron and copper are examples of metals that will change, easily and
dramatically, in reduction versus oxidation. However, cobalt doesn't seem
to care what the atmosphere is. It still turns out blue when by itself,
purple in a magnesium-rich glaze.
If you want iron browns, or copper greens, or the lovely aqua of copper
in a white glaze, you do very well with oxidation. There are other
examples.
This is a big area of study, and you've asked a large question which
can't be answered readily in an e-mail. Test, test, test and you'll quickly
see what looks good in oxidation. There are plenty of effects you can
achieve with oxidation which you can't get at all in reduction.
I hope this is at least a little helpful
Dave Finkelnburg
Idaho Fire Pottery
-----Original Message-----
From: J102551@AOL.COM
To: CLAYART@LSV.CERAMICS.ORG
Date: Monday, June 05, 2000 3:15 PM
Subject: Chun glazes?
>I fire ^ 10 porcelain in oxidation. I am really frustrated by the lack of
>glazes for this atmosphere. I fell in love with porcelain because of the
>chun I used in school. I still love my porcelain but I am getting
>discouraged. Is it possible to get the affects of a Hun in oxidation? Are
>there other glazes that are interesting in oxy. Is it possible to tell by
>looking at a glaze formulae whether or not it will work in oxy? Help.
>Please? Jeri in Hastings.
>
>___________________________________________________________________________
___
>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.
>
J102551@AOL.COM on mon 5 jun 00
I fire ^ 10 porcelain in oxidation. I am really frustrated by the lack of
glazes for this atmosphere. I fell in love with porcelain because of the
chun I used in school. I still love my porcelain but I am getting
discouraged. Is it possible to get the affects of a Hun in oxidation? Are
there other glazes that are interesting in oxy. Is it possible to tell by
looking at a glaze formulae whether or not it will work in oxy? Help.
Please? Jeri in Hastings.
Ray Aldridge on tue 6 jun 00
At 05:24 PM 6/5/00 -0600, you wrote:
>Jeri,
> The simple answer to your questions is yes, yes and yes!
> Regarding a Chun, or Jun as it is now spelled, Robert Fournier, in his
>"Illustrated Dictionary of Practical Pottery," says a Jun glaze is,
>"unaffected by kiln atmosphere except that the body color will show through
>to a degree..."
I'm no expert, but this was not my experience with Chun glazes. An
oxidized patch on an otherwise blue Chun tended to be yellow, just like an
oxidized celadon.
Since I'm firing porcelain in oxidation now, I'd love to find out that I'm
wrong.
Ray
Aldridge Porcelain and Stoneware
http://www.goodpots.com
Jeff Lawrence on wed 7 jun 00
Jeri was asking about chun glazes for cone 10 oxidation...
Hi Jeri,
Thanks for bringing this up. I've been puzzling over the same thing. Many of
the attributes Kingery & Vandiver ascribe to Song glazes don't appear (to my
reading) to hinge on reduction. To quote:
Students of Chinese porcelain agree that the most important feature of the
Song wares is the glaze, which is thick and translucent and much appreciated
for its lustrous yet coudy appearance, in contrast to the brightness of the
T'ang lead glazes ant the transparent glazes of subsequent dynasties. Soft,
aethetically pleasing colors are described as sea green, grayish green, etc.
Many studies have shown that these variations are based on iron as the
primary coloring constituent, and that the silky surface, depth of color,
translucency and opalescence result from diffuse reflection and refraction
caused by optical inhomogeneities within the glaze. These inhomogeneities
include liquid-liquid phase separation a few tens of nanometers in extent,
anorthite crystals, wollastonite crystals, undissolved batch material,
cristobalite crystals, and glaze bubbles ranging in size from the
submicrosopic up t nearly a millimeter in diameter.
End quotation.
To me, the only thing in there that spells reduction is the reduced iron
color. In theory, all you'd have to do is replace the iron with some copper
for color and some extra flux. I, too, am curious about how this pans out in
reality.
Any glaze gurus out there care to comment on this?
Jeff Lawrence vox: 505 753 5913
Sun Dagger Design fax: 505 753 8074
18496 US HWY 84/285 jml@sundagger.com
Espanola NM 87532 www.sundagger.com
See: "Song Dynasty Jun (Chun) Ware Glazes" by Kingery-Vandiver (American
Ceramic Society, Vol 62, no 11, 1983).
Des Howard on thu 8 jun 00
>
> Ray Aldridge wrote:
>
> I'm no expert, but this was not my experience with Chun glazes. An
> oxidized patch on an otherwise blue Chun tended to be yellow, just like an
> oxidized celadon.
>
> Since I'm firing porcelain in oxidation now, I'd love to find out that I'm
> wrong.
>
Ray
Our standard blue glaze is not affected by kiln atmosphere
Blue/White - Reduced or Oxidised
Cone 11- Satin white
Cone 11-12 Blue
Cone 12+ Clear
Blue/White + Copper - Reduced
Cone 11- Satin Pink
Cone 11-12 Purple/Blue
Cone 12+ Clear
Blue/White + Copper - Oxidised
Cone 11- Satin Green
Cone 11-12 Green/Blue
Cone 12+ Clear
I gather that this glaze is an emulsion type, relying on suspended
globules to produce the blue colour, if your glaze uses an iron addition
that in my experience would be blue in reduction & amber in oxidation.
I'll try to get some pics uploaded to our site.
Des
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.lisp.com.au
J102551@AOL.COM on thu 8 jun 00
Ron, I have a lot of yucky test tiles with that really unpleasant yellow.
Some are almost clear with crazing and some are opaque but they are all
yucky. These are glazes that are gorgeous and foolproof in reduction. Like
Val's Colemanite and a great blue chun that will go from blue to pink to
white with lavender streaking, and everything in between. Jeri
Lee Love on fri 9 jun 00
----- Original Message -----
From: Des Howard
| I gather that this glaze is an emulsion type, relying on suspended
| globules to produce the blue colour, if your glaze uses an iron addition
| that in my experience would be blue in reduction & amber in oxidation.
| I'll try to get some pics uploaded to our site.
Des,
Chun uses Iron and boneash for its coloration (the phosphorus in
boneash creates tiny bubbles that help create the white color, so a real
Chun is dependant upon reduction. Mine can be a buttugly grey if there is
not enough reduction. Here is the one I use:
Paul Morse's Chun
C. Feldspar 80
Whiting 7
Flint 7
Softwood ash 4
Bone Ash 2
Yellow Ochre 1
Bentonite 1
For purple Splash: 3% copper slip on raw body.
--
Lee Love
Nanai , Mashiko-machi ,Tochigi-ken 321-4106 JAPAN Ikiru@kami.com
Voice Mail and Faxes (a USA number): (303) 256-0374
Help E.T. Phone Earth: http://setiathome.ssl.berkeley.edu/
Paul Taylor on sun 11 jun 00
Dear Jerie.
This question of yours turned my view of ceramics upside down mixing my
head and my metaphors. I am posting this letter even though it reflects the
confusion.
All glazes work in Oxidation that work in reduction in so much as they
flux. Chun glazes as far as I know are reduction glazes there is a technique
by which you can add the finest silicon carbide to a oxidized fired glaze to
reduce it locally how reliable that is I do not Know. I have never seen pots
made commercially using this technique . Oxidation produces every color
imaginable. You can produce Celedon using copper that are very similar to
the sung Celedon and a lot better than the watery olive greens that us
reduction potters try to pass off as Celedon.
Temocus work as well in ox as reduced You can put them on course iron
rich body, fire them high and soak them or ramp them for hares fur and oil
spotting. I add some colemenite (gerstley borate and bone ash).under a white
glaze or a matt glaze you get lots of interesting effects.
All the stains work brilliantly. Use a satin matt or aventurine glazes
as a base . Again soak and ramp. The secret is not to over fire the glaze
destroying the crystals nuclei. pottery can be strangely conservative there
is a snobbery against stains and oxidation and a obsession with fancy firing
effects.
Most reduction potters use salt glaze and shinoes fired in wood. these
glazes record the drama of the fire they are a long way from sung Celedon.
But you want to make classical han type glazes. It depends on the quality
you are looking for there is a depth of feeling in a reduced glaze that is
difficult to get in oxidation and I suspect that is what intrigues you. an
opalescent glaze that is blue flashing purple pink if washed with copper. I
doubt if you can do this in an oxidized kiln.
However do not be fooled into thinking that there is any potter glazing
commercially with this sort of quality even if they are reducing. We all
know how the classical glazes were made but we can not make them ourselves.
Margaret Friths blue Celedon is the only one that comes near. It is possible
to make a bright olive green that works well over scarfitoe which gives it
some lift. but no one to my Knowledge produces an opalescent rich green
that has a life of it,s own, even with all our flash technology.
Copper reds are reputedly possible with silicon carbide added but I know
of no one producing them in this way. There could be good reason for that
either I do not Know of them or it is not reliable or sufficient attention
has not been given to the research to get the firing and the recipes
reliable. Even in reduction copper reds are difficult. Nigel woods In a
ceramic review article explains how to make one in great detail but he
omitted to give details of the firing cycle which is more important than the
recipe. The potters producing consistent copper reds full time, not piebald
pinks, use some very expensive technology. Forced air and gas kilns if only
I could afford one.
Takeshida Yasuda has been working away on some very interesting oxidized
glazes you should see them they will inspire you with the knowledge that
Oxidation has a lot to offer. He is very generous with his information so he
must have published something about how he does it. He is giving a lecture
in Belfast Ireland 30 june to I july on contact byrnetina@hotmail.ie. price
65 Irish pounds. I am going.
A fault of mine is to blame the glaze on a undefined pot. Where as a
salt glaze, ash or shino will make a mediocre pot good an oxidized glaze
will make a good pot rather plain. You have to exaggerate its features in
the making to balance the oxidized glaze. It is ironic that the simpler
firing takes less prisoners. I suspect it is to do with the sculpture of the
pot having no distractions.
I heard David leach in one of his demose explain the iron rich clay
fired in reduction as whole meal pottery and you must know how bland and
chewey badly made whole meal anything can be. As you can see I am no longer
impressed by reduction but I keep trying.
But should I keep trying. Can quality effects be got in oxidation is my
gas kiln just a fuel guzzling white elephant. So I am going to get some
decent stains and see what I can come up with.
Regards Paul Taylor
> From: J102551@AOL.COM
> Reply-To: Ceramic Arts Discussion List
> Date: Mon, 5 Jun 2000 14:37:28 EDT
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Chun glazes?
>
> I fire ^ 10 porcelain in oxidation. I am really frustrated by the lack of
> glazes for this atmosphere. I fell in love with porcelain because of the
> chun I used in school. I still love my porcelain but I am getting
> discouraged. Is it possible to get the affects of a Hun in oxidation? Are
> there other glazes that are interesting in oxy. Is it possible to tell by
> looking at a glaze formulae whether or not it will work in oxy? Help.
> Please? Jeri in Hastings.
>
> ______________________________________________________________________________
> 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.
Coyotbeth@AOL.COM on sun 11 jun 00
Hi Paul,
Do you know of a website for Takeshida Yasuda? Would love to see his work.
TIA
Beth
| |
|
