Chris Greenman on sun 18 jun 06
Here I go again. This time with photo documentation. I fired this load
without reducing until 06 had gone down on bottom. Really had to restrain
myself but alas the bubbles return...I am very frustrated on this problem...
I got some good suggestions on the last go round. Anybody else want to help
here??
link to photos: http://cgreenman.zaadz.com/photos
no comments on the wood fired work?
Thanks,
Chris
Earl Brunner on mon 19 jun 06
I know shino's can be bad this way (real stiff), but they look underfluxed to me............
Chris Greenman wrote: Here I go again. This time with photo documentation. I fired this load
without reducing until 06 had gone down on bottom. Really had to restrain
myself but alas the bubbles return...I am very frustrated on this problem...
I got some good suggestions on the last go round. Anybody else want to help
here??
link to photos: http://cgreenman.zaadz.com/photos
no comments on the wood fired work?
Thanks,
Chris
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Earl Brunner
e-mail: brunv53@yahoo.com
Ruth Ballou on mon 19 jun 06
Hi Chris,
Of course, you know that many would do any thing to get this effect....
Give us a little more information.....What's the recipe? What clays
are you using it on? How much iron or grog is in the clay? Does it do
this on porcelain? More questions than answers.
My best guess is that it's a combination of the clay body and the
glaze recipe. Your photos seem to show that the clay is fairly high
in iron. And I'm wondering if the shino recipe is one of the soda ash
varieties. Add long/heavy reduction to the mix, and that means a lot
of gas has to make its way through the glaze. Shinos are very stiff
glazes, typically high in alumina. Not much chance that bubbles
created by out gasing will have a chance to heal over. That bowl
seems to be showing intact bubbles. How high is the alumina in your
shino?Also, shino can have spotty coverage in the trimmed areas of
pots where grog may come through to the surface.
I'm also wondering about your bisque temperature. And how thick is
the glaze in the bucket? Does the glaze look bubbly when it goes on
the pot? If the pots were bisqued at a lower temperature, the glaze
could be thinner in the bucket, perhaps giving any bubbles in the raw
state a better chance of dispersing. In Theory.
If it were me, I'd try the simple, basic shino recipe and your shino
on clays with varying amounts of iron and grog. I'd apply some tests
to a lower temperature bisque, maybe even to greenware and leather
hard. I'd soak some of the tests in a soda ash solution to see if
that recreates the bubbles. If you don't have it, the simple shino is
70 - 80 % Neph Sye and 30 - 20% kaolin. Also, see if you can get your
hands on the Studio Potter issue with Jim Robison's article about
shino. It has about 50 different shino recipes and lots of information.
Giving it my best shot....
Ruth Ballou
Belgium
On Jun 19, 2006, at 1:04 AM, Chris Greenman wrote:
> Here I go again. This time with photo documentation. I fired this load
> without reducing until 06 had gone down on bottom. Really had to
> restrain
> myself but alas the bubbles return...I am very frustrated on this
> problem...
> I got some good suggestions on the last go round. Anybody else want
> to help
> here??
>
> link to photos: http://cgreenman.zaadz.com/photos
>
> no comments on the wood fired work?
>
> Thanks,
>
>
> Chris
>
> ______________________________________________________________________
> ________
> 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.
Chris Greenman on tue 20 jun 06
The Shino recipie is Neph Sy 39.3;Spodumene 30.3; OM4 17.2; Soda Ash 8; EPK
4.8. I have been using soldate 60 a white stoneware from lagunna. I used
this clay for about six years and recently switched to using zella stone a
nice toasty brown stoneware from highwater clays and Dick Lehmans dirty
porcelain. I am using these clays now because I wanted a tighter more iron
inthe clay for woodfiring and wanted to try them both with shino.
I was getting tired of the soldate with its more gritty surface after wood
firing. It is a good all purpose clay body though. The bubbles are pervasive
on all of the clays. Maybe worse on the soldate 6o. On the large
bowl -soldate 60. On the mugs - zella stone. I bisque to 04. I started
reduction on the last firingg at roughly 06 very late for me. This shino has
worked great for me for years. But in the last year or so it has bubbled.
Joyce and Ruth I am not sure why anyone would like the bubbled shino. It
bubbles out of control. SO much that the large and small bubbles are easily
popped and would pose a danger to a consumer. Yes I do like shino because of
the bubbles that heal and for other textures that shino can create, But
these nasty bubbles are a nusance and are dangerous. When I sand the bubbles
with emory cloth the thin layer left is grey where the area around it is
whiter.
I do tend to like my shino to go on thick. That has produced a dusty off
white with some orange browns in thinner areas. I also like shino over shino
to get variations of whites. But I have done this in the past and it has
worked. I also use the glaze at school and get better results there. We get
bubbles but there the bubbles heal.
Now the other photos on the zaadz site are from frings in Fat Bastard the
anagama kiln at the University of Montevallo in ALabama. I used shino --same
batch for a liner in all of those pieces and no problem. Maybe I am reducing
to much during my firings at home so the shino bubbles and does not have a
chance to heal.
I do not have the Jim Robinson shino article. But I do have the Shino
catolog from the "American Shino The Glaze of a thousand faces" that is a
great book. It has a lot of recipies. SOme I have tried. I also have
collected a lot of shino glazes from clay art ove the years. In fact the
recipie above I orginally got off of clayart.
Thank you for your help Joyce and Ruth and others.
When you can please send send some rain.
Chris
in Montgomery Al
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of Ruth Ballou
Sent: Monday, June 19, 2006 10:06 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Troubles with bubbles--shino see the photos
Hi Chris,
Of course, you know that many would do any thing to get this effect....
Give us a little more information.....What's the recipe? What clays
are you using it on? How much iron or grog is in the clay? Does it do
this on porcelain? More questions than answers.
My best guess is that it's a combination of the clay body and the
glaze recipe. Your photos seem to show that the clay is fairly high
in iron. And I'm wondering if the shino recipe is one of the soda ash
varieties. Add long/heavy reduction to the mix, and that means a lot
of gas has to make its way through the glaze. Shinos are very stiff
glazes, typically high in alumina. Not much chance that bubbles
created by out gasing will have a chance to heal over. That bowl
seems to be showing intact bubbles. How high is the alumina in your
shino?Also, shino can have spotty coverage in the trimmed areas of
pots where grog may come through to the surface.
I'm also wondering about your bisque temperature. And how thick is
the glaze in the bucket? Does the glaze look bubbly when it goes on
the pot? If the pots were bisqued at a lower temperature, the glaze
could be thinner in the bucket, perhaps giving any bubbles in the raw
state a better chance of dispersing. In Theory.
If it were me, I'd try the simple, basic shino recipe and your shino
on clays with varying amounts of iron and grog. I'd apply some tests
to a lower temperature bisque, maybe even to greenware and leather
hard. I'd soak some of the tests in a soda ash solution to see if
that recreates the bubbles. If you don't have it, the simple shino is
70 - 80 % Neph Sye and 30 - 20% kaolin. Also, see if you can get your
hands on the Studio Potter issue with Jim Robison's article about
shino. It has about 50 different shino recipes and lots of information.
Giving it my best shot....
Ruth Ballou
Belgium
On Jun 19, 2006, at 1:04 AM, Chris Greenman wrote:
> Here I go again. This time with photo documentation. I fired this load
> without reducing until 06 had gone down on bottom. Really had to
> restrain
> myself but alas the bubbles return...I am very frustrated on this
> problem...
> I got some good suggestions on the last go round. Anybody else want
> to help
> here??
>
> link to photos: http://cgreenman.zaadz.com/photos
>
> no comments on the wood fired work?
>
> Thanks,
>
>
> Chris
>
> ______________________________________________________________________
> ________
> 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.
____________________________________________________________________________
__
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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Ivor and Olive Lewis on tue 20 jun 06
Dear Chris Greenman,=20
If we think we have troubles you should consider the Floor Tile =
Industry. They have a classification table which ranges from "Small =
Holes" and "Pores" to "Pox" and "Crow Feet". INTERCERAM will be =
publishing the second part of a report presented at the 2004 Conference =
on Tile quality. In the part that I have read it gives the following =
observation and conclusion from a series of thermal gradient firings.
"...the glaze has many small pores (10-30 mu) up to a firing =
temperature o 1370 deg C. Between 1370 deg C and 1400 deg C the bubble =
surface content increases rapidly up to 20% at the glaze body interface =
with some very large bubbles indicating overfiring to be a possible =
problem cause. This confirms that changing solubility characteristic of =
specific glaze components and the lower viscosity at higher temperatures =
have an effect on porcelain glazes"=20
Perhaps the next issue will give us useful information. Once they give =
the gas analysis we can make some informed speculation about your glaze.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
John Britt on tue 20 jun 06
Chris,
I have done a lot of work with shinos and found that if I reduce really
early (heavily below cone 012, I have even started as early as 600F) on a
high iron body it will gas off and create bubbles in the glaze coat (which
is still dry and unvitrified) and since the glaze is not very fluid (high
alumina) the bubbles will never heal over. This particularly happens with
a glaze called Mino (high alumina shino).
Some bubbles later are not a problem and can be attractive but too early
is a frothy mess. Sand blasting them makes a nice sculptural surface
though.
Hope it helps,
John Britt
www.johnbrittpottery.com
Ron Roy on wed 21 jun 06
Hi Chris,
Perhaps - if you send me the recipe - I can compare with other shino's and
see if the solution lies there.
Does it only happen in some parts of the kiln?
Just catching up on email and found the recipe.
When I calculate it out - I see - compared to my shino (it's in the
American shino book) I have to add another 15 EPK to get the alumina
content up to whats in mine - I calculated without the soda ash by the way.
I have to conclude that the glaze is overfired - but if the bubbles smooth
out in a slower cooling kiln then perhaps you have to slow cool it.
There is also a lot of OM#4 which can vary a lot and this might explain
what happened to this batch?
I could refomulate with more EPK and less Old Mine if you want to experiment?
RR
>Chris Greenman wrote: Here I go again. This time
>with photo documentation. I fired this load
>without reducing until 06 had gone down on bottom. Really had to restrain
>myself but alas the bubbles return...I am very frustrated on this problem...
>I got some good suggestions on the last go round. Anybody else want to help
>here??
>
>link to photos: http://cgreenman.zaadz.com/photos
>
>no comments on the wood fired work?
>
>Thanks,
>
>
>Chris
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Edouard Bastarache Inc. on wed 21 jun 06
Ron,
for once I agree with you (Hehehehehehe).
"There is also a lot of OM#4 which can vary a lot
and this might explainwhat happened to this
batch?"
I have been using the same batch of OM#4 and I
seem to get surface flaws in Shinos quite more
often than in those made with other clays, kaolins
or ball clays.
Later,
Edouard Bastarache
Membre de La French Connection
Member of The French Connection
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.wanadoo.fr/smart2000/index.htm
http://www.flickr.com/photos/potier/
http://oldringer.blogspot.com/
http://albertpeintures.blogspot.com/
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