Lisa P Skeen on thu 5 apr 01
Weird thing about me: None of the glazes I use are earth tones. BUT, when I buy pots, I'm likely to
get the one with shino or tenmoku glaze. My fave shinos are the ones that go iridescent.
What makes the iridescence in some shinos? Why can the same shino be fat and white breaking
orange AND iridescent, on 2 different pots side by side in the same kiln?
L
Hank Murrow on thu 5 apr 01
>Weird thing about me: None of the glazes I use are earth tones. BUT,
>when I buy pots, I'm likely to
>get the one with shino or tenmoku glaze. My fave shinos are the ones that
>go iridescent.
>
>What makes the iridescence in some shinos? Why can the same shino be fat
>and white breaking
>orange AND iridescent, on 2 different pots side by side in the same kiln?
>
Dear Lisa;
Almost always the irridescence is the result of soluble materials in the
glaze. In the case of shinos it is the soda ash found in many. Glazes which
contain unwashed wood ash often have this irridescence, as seen in black
Seto teabowls.
Hank in Eugene
L. P. Skeen on thu 5 apr 01
Tanks for the explanation. My friend Leanne has a faboo shino that she just
THROWS iron into. (What? There's just a bit more left in the container?
Well hell, just toss it in there - measurement, schmeasurement. ;) ) When
it came out of Charlie Riggs' wood kiln it looked like gold. I have seen it
come out of a gas kiln looking the same. Could never figure out if it was a
function of the smoke, redux, or what.
L
----- Original Message -----
> Almost always the irridescence is the result of soluble materials in the
> glaze. In the case of shinos it is the soda ash found in many.
Craig Martell on fri 6 apr 01
At 10:33 AM 4/6/01 -0400, you wrote:
>Do you know what produces the orange?
Hi:
I'm not Hank, he'll be along shortly.
The orange is produced by a small amount of iron in the glaze, or iron that
is taken from the claybody into the glaze. The composition of shinos, low
calcium and high alumina and silica, keeps the iron from being dissolved or
taken into solution by the glaze and very tiny iron crystals precipitate
and give lots of variations of orange and red. Small amounts of dissolved
iron would most likely give a celadon color.
That's the general idea.
regards, Craig Martell in Oregon
Gail Dapogny on fri 6 apr 01
Hank,
Do you know what produces the orange? I recently put shino on several
things. Some of them--too thick -- were simply light in color, a little
iridescent but not orange, except on the inside (cup). On the one that I
glazed too thinly, all I got was brown and a little iridescent. I'm still
frustrated, puzzled, and a little gunshy. It was Malcolm's formula, and I
even sprayed a little soda solution underneath.
---Gail
>>Weird thing about me: None of the glazes I use are earth tones. BUT,
>>when I buy pots, I'm likely to
>>get the one with shino or tenmoku glaze. My fave shinos are the ones that
>>go iridescent.
>>
>>What makes the iridescence in some shinos? Why can the same shino be fat
>>and white breaking
>>orange AND iridescent, on 2 different pots side by side in the same kiln?
>>
>
>Dear Lisa;
>
>Almost always the irridescence is the result of soluble materials in the
>glaze. In the case of shinos it is the soda ash found in many. Glazes which
>contain unwashed wood ash often have this irridescence, as seen in black
>Seto teabowls.
>
>Hank in Eugene
>
>______________________________________________________________________________
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>
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Gail Dapogny
1154 Olden Road
Ann Arbor, MI 48103-3005
(734) 665-9816
gdapogny@umich.edu
cyberscape on sat 7 apr 01
Gail,
What makes the orange in Malcolm's shino is the redart clay in the
formula on white clay. If you reduce very lightly, you will get more
orange, or if you wax the shino you will get orange. You could put
liquid wax over the whole thing and get really orange orange. The
application of soda ash increases the carbon trapping and gives you more
blacks an greys. The darker the clay the browner the shino will be.
Hope this helps.
Harvey Sadow
Lorraine Pierce on sat 7 apr 01
Hi Harry...at what stage of the making process does one 'wax the shino'?
How? Pour, rub, buff??? Thanks , Lori in New Port Richey Fl.
Hank Murrow on sat 7 apr 01
>Hank,
>Do you know what produces the orange in shinos? I recently put shino on
>several
>things. Some of them--too thick -- were simply light in color, a little
>iridescent but not orange, except on the inside (cup). On the one that I
>glazed too thinly, all I got was brown and a little iridescent. I'm still
>frustrated, puzzled, and a little gunshy. It was Malcolm's formula, and I
>even sprayed a little soda solution underneath.
>---Gail
>
Dear Gail;
Malcolm's recipe (at least the only one I know about) has a ton of soda ash
in it. Maybe he will chime in here somewhere. Maybe your recipes have too
much iron in them, whether from traces in the materials, or from the
claybods.
The "Indian Red" color that I identify with shino is arrived at by creating
a glaze very high in its alumina to silica ratio, reducing early to get
whatever iron may be present up to the surface (iron is really mobile when
reduced), giving a longish period of oxidation after reduction (or as I
have been advocating, a soak in oxidation during cooling). What you will
have after all this is a VERY THIN ferric(oxidized) microcrystalline
network on the surface of the glaze which will be that color we potters all
love. If there is too much silica in relation to the alumina, bad color. If
there is too much melting of the surface, bad color. So brushing on soad
ash may be counterproductive.
My shinos fall into the range of form 3.5/1 Si/Al to 4.4/1 Si/Al. None have
soda ash in them, All have some Li from some form of spodumene. Joyce or
Dannon can tell you the firecolor is pretty intense. My best one has 1.533
Alumina to 5.397 Silica. That's a ton of alumina, but it gives a nice
matrix for the ferric color to form within. Dannon has a plate with this
glaze on it. I have broken a lot of shino pieces to look underneath, and
everyone of them was white just under the red color. BTW, there is no added
iron in my recipe, just what comes along in all those 'white' powders!
At the Smithsonian Labs, Pamela Vandiver prepared some samples of my glazes
for examination with the electron scanning microscope and the microprobe.
We found that the red color is around 20 millionths of a meter (20 microns)
which is very, very thin. Makes a good case for avoiding abrasion with
these glazes. I recall Joe Bennion saying that he made an order of 500
pieces with his best shino for a restaurant, only to find that after a
month or two of that severe use, they all had a white ring on the up side
created by the foot of the plate that rested on it. He had to replace them
all!
I am pretty sure that my article "Shinos in the Fire....an Odyssey" will
come out soon, and then the recipes and firing r=E9gime will be 'out there'.
Meanwhile, look at the recipes for your glazes and try the oxidizing soak,
and report back.
Cheers, Hank in Eugene
Jan Cannon on sun 8 apr 01
I've been working on a new Shino this winter and it is in the same range as
the Shino that Hank describes in his post below. I am pleased with the
orange and red that I am getting from it. The Si:Al ratio of my glaze is
4.26/1 (Al2O3 1.22/SiO2 5.21). I am also not using any soda ash. Examples
of this glaze are on the "Portfolio" page of my website. On the second row
from the top are two Shino pieces. The one on the left is Shino over a
white slip, over a stoneware body and the one to the right is just Shino
over a stoneware body, with inlay decoration. There is also another example
of this glaze on the second row from the bottom, the vase on far right.
I do a good solid reduction firing, with a six hour oxidizing soak from
about cone 10 to 11. I then let the kiln cool to about 1800 F. and then
soak the kiln for an hour or so there (oxidizing). I really can't imagine
that this is doing anything but haven't not done it to prove it
conclusively. One amazing way that I do get color is just by putting
finished pieces with less orange and red color than I would like in with a
bisque firing. It is radical how much color is picked up. I have no idea
the mechanism of this but the results are dramatic. One other thing you do
get when you re-fire this was is a finer secondary network of crazing, which
I like. I don't have any examples of this on my site though but in the
future I will put a before and after picture up there to illustrate this.
I got the idea about the long oxidizing soak at high temperature and
re-firing in a bisque from Ian Currie's "Stoneware Glazes: A Systematic
Approach," a must have book for anyone who wants to understand stoneware
glazes. He has a chapter on Shino glazes there too.
Jan Cannon Pottery
19 Garen Road
Charlotte, VT 05445
Tel: 802-425-6320
jan@jancannonpottery.com
www.jancannonpottery.com
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of Hank Murrow
Sent: Saturday, April 07, 2001 2:08 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: What makes Shino work?
>Hank,
>Do you know what produces the orange in shinos? I recently put shino on
>several
>things. Some of them--too thick -- were simply light in color, a little
>iridescent but not orange, except on the inside (cup). On the one that I
>glazed too thinly, all I got was brown and a little iridescent. I'm still
>frustrated, puzzled, and a little gunshy. It was Malcolm's formula, and I
>even sprayed a little soda solution underneath.
>---Gail
>
Dear Gail;
Malcolm's recipe (at least the only one I know about) has a ton of soda ash
in it. Maybe he will chime in here somewhere. Maybe your recipes have too
much iron in them, whether from traces in the materials, or from the
claybods.
The "Indian Red" color that I identify with shino is arrived at by creating
a glaze very high in its alumina to silica ratio, reducing early to get
whatever iron may be present up to the surface (iron is really mobile when
reduced), giving a longish period of oxidation after reduction (or as I
have been advocating, a soak in oxidation during cooling). What you will
have after all this is a VERY THIN ferric(oxidized) microcrystalline
network on the surface of the glaze which will be that color we potters all
love. If there is too much silica in relation to the alumina, bad color. If
there is too much melting of the surface, bad color. So brushing on soad
ash may be counterproductive.
My shinos fall into the range of form 3.5/1 Si/Al to 4.4/1 Si/Al. None have
soda ash in them, All have some Li from some form of spodumene. Joyce or
Dannon can tell you the firecolor is pretty intense. My best one has 1.533
Alumina to 5.397 Silica. That's a ton of alumina, but it gives a nice
matrix for the ferric color to form within. Dannon has a plate with this
glaze on it. I have broken a lot of shino pieces to look underneath, and
everyone of them was white just under the red color. BTW, there is no added
iron in my recipe, just what comes along in all those 'white' powders!
At the Smithsonian Labs, Pamela Vandiver prepared some samples of my glazes
for examination with the electron scanning microscope and the microprobe.
We found that the red color is around 20 millionths of a meter (20 microns)
which is very, very thin. Makes a good case for avoiding abrasion with
these glazes. I recall Joe Bennion saying that he made an order of 500
pieces with his best shino for a restaurant, only to find that after a
month or two of that severe use, they all had a white ring on the up side
created by the foot of the plate that rested on it. He had to replace them
all!
I am pretty sure that my article "Shinos in the Fire....an Odyssey" will
come out soon, and then the recipes and firing r=E9gime will be 'out there'.
Meanwhile, look at the recipes for your glazes and try the oxidizing soak,
and report back.
Cheers, Hank in Eugene
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