Tony Ferguson on wed 19 feb 03
Connie,
Welcome to the world of shino--there are so many variable that can affect
how a shino will turn out--so that is why I glaze with 15 or more glazes as
I figure I will get something nice when others will not turn out. Although,
I have gotten better, but let me knock on some wood.
Sounds like you over-oxidized the shino--I have had entire loads of grey
white--which actually happens to be the traditional shino color range, not
the American reds, rusts and oranges.
Have fun--it is a perilous but rewarding journey.
Thank you.
Tony Ferguson
On Lake Superior, where the sky meets the Lake
Stoneware, Porcelain, Raku and more
by Coleman, Ferguson, Winchester...
www.aquariusartgallery.com
218-727-6339
315 N. Lake Ave
Apt 312
Duluth, MN 55806
----- Original Message -----
From: "Connie Woodward"
To:
Sent: Wednesday, February 19, 2003 12:26 PM
Subject: shino glaze mix changing after time?
> I mixed up a big batch of a shino that I had sampled and liked.
> I used it the next day and it turned out like the sample,
> then a couple of weeks later I used it from the same bucket
> again, and I got a completely different result, you would
> swear it wasn't even from the same glaze. The first time
> it was a pretty golden orange color, the later time it was
> a ugly white-grey. I fired them close to the same.. I don't
> have a oxy-probe so I go by flame size for the amount of
> reduction and the other pots in the kiln turned out like
> expected, so I don't think I was too far off with the firing.
>
> Has anyone heard of this happening with shinos?
>
> Thanks,
>
> Connie
>
> ============================================================
> Connie Woodward Karattopp Pottery 713-256-5907
> Navasota, TX www.karattopp.com connie@karattopp.com
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
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melpots@pclink.com.
>
Dannon Rhudy on wed 19 feb 03
Subject: shino glaze mix changing after time?
> I mixed ...shino that I had sampled and liked.
> .it turned out like the sample,
> then a couple of weeks later I used it from the same bucket
> again, and I got a completely different result,......
Ah, the shino puzzle raises it's head again. There is a ton of
information re: shino glazes in the archives. But the short
answer is, yes, shino can look very different from the same
glaze batch. It's not so much that the shino changes in the
bucket (though it might change a bit). Shino glazes are
very sensitive to a) thickness of application and b) temperature
of early reduction. Thick shino is white or cream, thin is
orange or reddish, depends on the recipe. If reduction is
started too late in the firing, the glaze will be very bland.
Cone 012 is not too soon to start reduction. If the kiln
cools slowly, the glaze will be more orange (the slow cool
gives some time for the iron to migrate to the surface). Take
a look at Hank Murrow's website. Carbon trap glazes
are tricky, and shino is #1 in this regard. But it is beautiful
when it works. Just takes some experience to get reliable
results. I repeat: check the archives.
regards
Dannon Rhudy
Connie Woodward on wed 19 feb 03
I mixed up a big batch of a shino that I had sampled and liked.
I used it the next day and it turned out like the sample,
then a couple of weeks later I used it from the same bucket
again, and I got a completely different result, you would
swear it wasn't even from the same glaze. The first time
it was a pretty golden orange color, the later time it was
a ugly white-grey. I fired them close to the same.. I don't
have a oxy-probe so I go by flame size for the amount of
reduction and the other pots in the kiln turned out like
expected, so I don't think I was too far off with the firing.
Has anyone heard of this happening with shinos?
Thanks,
Connie
============================================================
Connie Woodward Karattopp Pottery 713-256-5907
Navasota, TX www.karattopp.com connie@karattopp.com
Liz Willoughby on thu 20 feb 03
Dear Connie,
This has been my experience with using shino. Pots can be stacked
right next to each other and there will be a difference in color and
carbon trapping. It is never a sure thing. The grey means you got
some carbon trapping. Usually if the glaze is applied a little on
the thick side it will be whiter, thinner it will be more orange.
Clay bodies with just a little iron in them will be richer in color,
usually darker (more orange) with more depth. If you get the shino
bug it is an irresistible glaze. Get the June 2002 issue of Studio
Potter, lots of info in there, also Clay Times had a series of
articles by Pete Pinnell a couple of years ago that is explains ALL
about shinos.
Best of luck, Meticky Liz
>I mixed up a big batch of a shino that I had sampled and liked.
>I used it the next day and it turned out like the sample,
>then a couple of weeks later I used it from the same bucket
>again, and I got a completely different result, you would
>swear it wasn't even from the same glaze. The first time
>it was a pretty golden orange color, the later time it was
>a ugly white-grey. I fired them close to the same.. I don't
>have a oxy-probe so I go by flame size for the amount of
>reduction and the other pots in the kiln turned out like
>expected, so I don't think I was too far off with the firing.
>
>Has anyone heard of this happening with shinos?
>
>Thanks,
>
>Connie
Liz Willoughby
RR 1
2903 Shelter Valley Rd.
Grafton, On.
Canada
K0K 2G0
e-mail lizwill@phc.igs.net
Paul Herman on thu 20 feb 03
Hank and Shino Lovers,
This information from Hank makes a lot of sense. After all, what
phenomenon would cause iron to "migrate" within the glaze melt, during
the cooling cycle? TIME and oxygen are working on the small amount of
iron present at the glaze surface.
I've been experimenting with shino glazes for a few years now, and came
to the conclusion to fire them only in the big wood kiln. With a long
firing and slow cooling, their character has a chance to come out. It's
not that they are BAD in the gas, just very different. The big kiln
makes them smoother, warmer, etc. At their best, (IMHO) they get a kind
of iridescence that is hard to describe, a surface effect, but deep and
mysterious.
I suppose slow cooling, or firing down in the gas kiln would get better
results.
Best wishes,
Paul Herman
Great Basin Pottery
423-725 Scott Road
Doyle, California 96109 US
potter@psln.com
----------
>From: Hank Murrow
> Dear Dannon and original questioner;
>
> I absolutely believed this too. Pam Vandiver (of the Smithsonian) and I
> have looked at microprobe analysis results taken from the glaze
> interface to the surface, finding NO difference in the amounts of iron
> at these varying sites. So it isn't that the iron migrates to the
> surface IMHO. The slow cooling gives what iron there is in the glaze
> the time to form the micro-crystals that produce the color.
>
> Cheers, Hank in Eugene www.murrow.biz/hank
Hank Murrow on thu 20 feb 03
On Wednesday, February 19, 2003, at 03:38 PM, Dannon Rhudy wrote:
> Subject: shino glaze mix changing after time?
>
>> I mixed ...shino that I had sampled and liked.
>> .it turned out like the sample,
>> then a couple of weeks later I used it from the same bucket
>> again, and I got a completely different result,......
>
> Ah, the shino puzzle raises it's head again. SNIP>>>>> If the kiln
> cools slowly, the glaze will be more orange (the slow cool
> gives some time for the iron to migrate to the surface). Take
> a look at Hank Murrow's website.
Dear Dannon and original questioner;
I absolutely believed this too. Pam Vandiver (of the Smithsonian) and I
have looked at microprobe analysis results taken from the glaze
interface to the surface, finding NO difference in the amounts of iron
at these varying sites. So it isn't that the iron migrates to the
surface IMHO. The slow cooling gives what iron there is in the glaze
the time to form the micro-crystals that produce the color.
Cheers, Hank in Eugene www.murrow.biz/hank
Merrie Boerner on sat 22 feb 03
My wood burning kiln is a simple rectangle with a lower fire box in
front....easy to build and easy to fire. We could get cone 13 in 24 hours if
we wanted to....but, for the sake of shino, and since we are trying to
control the passion of the flame....AND because Nils and Jack told me to
"fire longer and cool slower".....we hold at 2000 degrees F. for hours
(sometimes 12) until cone 10 is over in the back and then we go up and down
a bit to paint the pots with ash and flash.
Tony C.......I wanted to respond to your query about cones bending at 2000*
over time....but I take shitty firing notes and then I can't find them. The
archives ARE full of Time , Temperature, and Cones.....but, I will tell
you.....only use that pyrometer to guide up and down temp, not true temp.
Swimming in Mississippi,
Merrie
Daffodils are blooming !
Roger Korn on sat 22 feb 03
Paul Herman wrote:
>Hank and Shino Lovers,
>
>This information from Hank makes a lot of sense. After all, what
>phenomenon would cause iron to "migrate" within the glaze melt, during
>the cooling cycle? TIME and oxygen are working on the small amount of
>iron present at the glaze surface.
>
>I've been experimenting with shino glazes for a few years now, and came
>to the conclusion to fire them only in the big wood kiln. With a long
>firing and slow cooling, their character has a chance to come out. It's
>not that they are BAD in the gas, just very different. The big kiln
>makes them smoother, warmer, etc. At their best, (IMHO) they get a kind
>of iridescence that is hard to describe,
>
I have just seen some of the shinos from the first firing of the new
double-catenary single-stack wood kiln that was built by Jason Hess and
students at Northern Arizona University. This firing reached ^10 in ~24
hours and was held for an additional 6 hours, then cooled completely
shut up. Compared to the same glaze fired in the traditional 4-5 day
anagama cycle, there is less irridescense, but greater "clarity" to the
fired result. Colors are similar, but the long firing definitely
increases the irridescense and complexity of the results.
The almost abalone-shell irridescense of some of Paul's shinos has to be
seen to be believed. I could spend hours gazing at a single piece,
fantastic details revealing themselves successively as I explore further
into the details. Hypnotic.
Roger
>a surface effect, but deep and
>mysterious.
>
>I suppose slow cooling, or firing down in the gas kiln would get better
>results.
>
>Best wishes,
>
>Paul Herman
>Great Basin Pottery
>423-725 Scott Road
>Doyle, California 96109 US
>potter@psln.com
>
>----------
>
>>From: Hank Murrow
>>
>
>>Dear Dannon and original questioner;
>>
>>I absolutely believed this too. Pam Vandiver (of the Smithsonian) and I
>>have looked at microprobe analysis results taken from the glaze
>>interface to the surface, finding NO difference in the amounts of iron
>>at these varying sites. So it isn't that the iron migrates to the
>>surface IMHO. The slow cooling gives what iron there is in the glaze
>>the time to form the micro-crystals that produce the color.
>>
>>Cheers, Hank in Eugene www.murrow.biz/hank
>>
>
>______________________________________________________________________________
>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.
>
--
Roger Korn
McKay Creek Ceramics
In AZ: PO Box 463
4215 Culpepper Ranch Rd
Rimrock, AZ 86335
928-567-5699 <-
In OR: PO Box 436
31330 NW Pacific Ave.
North Plains, OR 97133
503-647-5464
iandol on sat 22 feb 03
Dear Paul Herman,=20
You say <within the glaze melt, during the cooling cycle? TIME and oxygen are =
working on the small amount of iron present at the glaze surface.>>
I would like to know....what is the nature of the Iron as described in =
your statement. If it is already one of the oxides it is stable and =
possibly still solid at all temperatures up to Cone 12. If it is as a =
metal it will still be solid beyond cone 12.
I have no argument with the idea put forward by Hank other than to =
consider the atmosphere.
Best regards,
Ivor Lewis
Paul Herman on sat 22 feb 03
Greetings Ivor,
This is what I'm thinking about that.
When the kiln's fire is shut down, the iron in the glaze melt is in a
reduced state. I believe this reduced iron is in the form of black iron
oxide (Fe3 O4), not metallic iron. Is it the case that iron in glazes is
sometimes reduced all the way to metal?
During the slow cooling cycle of a large kiln, or controlled firing
down, the black iron oxide present on the surface of the glaze has a
chance to "re-oxidize" and become red iron oxide (Fe2 O3), producing
those nice warm colors. A way of seeing this is to look closely at a
shard, The surface is colored, sometimes quite darkly, and the rest of
the glaze is white or grey. I think the same principle is at work in
Iron-bearing clays fired in reduction. A warm brown surface, and grey
interior.
So, my answer to your question "what is the nature of the Iron?" is:
Black Iron Oxide dissolved within the melt, and during cooling, becoming
Red Iron Oxide on the surface. Could the red Iron be a precipitate?
Do you think I'm close, Ivor, or anyone?
With furrowed brow,
Paul Herman
Great Basin Pottery
423-725 Scott Road
Doyle, California 96109 US
potter@psln.com
----------
From: "iandol"
To: "Paul Herman"
Subject: Re: shino glaze mix changing after time?
Date: Fri, Feb 21, 2003, 10:21 PM
Dear Paul Herman,
You say <within the glaze melt, during the cooling cycle? TIME and oxygen are
working on the small amount of iron present at the glaze surface.>>
I would like to know....what is the nature of the Iron as described in
your statement. If it is already one of the oxides it is stable and
possibly still solid at all temperatures up to Cone 12. If it is as a
metal it will still be solid beyond cone 12.
I have no argument with the idea put forward by Hank other than to
consider the atmosphere.
Best regards,
Ivor Lewis
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