Elizabeth Priddy on thu 14 aug 08
if it is close enough in the kiln, as you indicated that you soak, sometime=
s
other colors will flash onto other glazes.
=A0
Unless you put it there by accident or marked it wrong, something migrated.
Elizabeth Priddy
Beaufort, NC - USA
Workshops and pottery online at:
http://www.elizabethpriddy.com
Natural Instincts Conference Information:
http://downtothepottershouse.com/NaturalInstincts.html
Kiln pictures and such:
http://www.flickr.com/photos/7973282@N03/
--- On Thu, 8/14/08, Timothy Joko-Veltman wrote:
From: Timothy Joko-Veltman
Subject: Am I out of my mind? (glaze-related)
To: CLAYART@LSV.CERAMICS.ORG
Date: Thursday, August 14, 2008, 6:01 PM
Took some glaze tests out of the kiln today. Some very nice and
informative. The one marked GB3b2 has got me stumped; the "b2" means
I added 2% copper to Glossy Base #3 (hence the "GB3"). It is not
anywhere NEAR green. I fire electric (14hrs up to 1280C and soaking
for 15 minutes, slow (18hrs) freefall cooling), so I really doubt I
accidently made a copper red. Besides, the color is wrong for that,
too. It is a - albeit beautiful - russet; a transparent reddish
brown. I am stumped. The only other colorant I used that day for
glaze tests was nickel - which can make a brown glaze, though I've
never seen a nickel brown this nice; first time for everything I
suppose. Also, the raw glaze REALLY looks like I added my
blacker-than-sin copper oxide, rather than the black nickel oxide I
use, which is black in name only (in fact it is a medium, vaguely
greenish, gray).
The recipe is (use at your own risk - this crazes on my body, and the
transparent test had microbubbles suspended in it):
46 Neph. Sy.
44 Quartz
10 Calcite (natural calcium carb.)
+ (for suspension)
3 Bentonite Volclay (a sodium bentonite)
0.1 MgSO4 (Epsom salt)
The unity for that (because I think I can pretty safely assume none of
you have access to analyses for my materials) is:
0.45 CaO
0.04 MgO
0.11 K2O
0.40 Na2O
0.51 Al2O3
5.32 SiO2
0.03 Fe2O3
0.01 TiO2
My clay body is a "white" stoneware, and fires greyish-white.
Is there any way this could actually be produced by copper? If so,
how to explain this result?
Regards,
Tim
=0A=0A=0A
Timothy Joko-Veltman on thu 14 aug 08
Took some glaze tests out of the kiln today. Some very nice and
informative. The one marked GB3b2 has got me stumped; the "b2" means
I added 2% copper to Glossy Base #3 (hence the "GB3"). It is not
anywhere NEAR green. I fire electric (14hrs up to 1280C and soaking
for 15 minutes, slow (18hrs) freefall cooling), so I really doubt I
accidently made a copper red. Besides, the color is wrong for that,
too. It is a - albeit beautiful - russet; a transparent reddish
brown. I am stumped. The only other colorant I used that day for
glaze tests was nickel - which can make a brown glaze, though I've
never seen a nickel brown this nice; first time for everything I
suppose. Also, the raw glaze REALLY looks like I added my
blacker-than-sin copper oxide, rather than the black nickel oxide I
use, which is black in name only (in fact it is a medium, vaguely
greenish, gray).
The recipe is (use at your own risk - this crazes on my body, and the
transparent test had microbubbles suspended in it):
46 Neph. Sy.
44 Quartz
10 Calcite (natural calcium carb.)
+ (for suspension)
3 Bentonite Volclay (a sodium bentonite)
0.1 MgSO4 (Epsom salt)
The unity for that (because I think I can pretty safely assume none of
you have access to analyses for my materials) is:
0.45 CaO
0.04 MgO
0.11 K2O
0.40 Na2O
0.51 Al2O3
5.32 SiO2
0.03 Fe2O3
0.01 TiO2
My clay body is a "white" stoneware, and fires greyish-white.
Is there any way this could actually be produced by copper? If so,
how to explain this result?
Regards,
Tim
Angela Davis on fri 15 aug 08
Hi Tim,
If that was my test I would be questioning myself too, something like;
1. Did the other tests with the copper ox look as
expected?
2. Is there any way I could have picked up the black iron ox
by mistake? manganese?
3. Did I mix up the recipes or dip the wrong tile?
I have several copper green glazes I've tested and gotten golden brown
results. Usually on red stoneware. I believe they also contained rutile.
I think I'll look them over again, I remember thinking some of the results
impossible.
You know you will have to run this test all over again to confirm the
results. :-)
Angela Davis
In Homosassa
----- Original Message -----
From: "Timothy Joko-Veltman"
To:
Sent: Thursday, August 14, 2008 6:01 PM
Subject: Am I out of my mind? (glaze-related)
> Took some glaze tests out of the kiln today. Some very nice and
> informative. The one marked GB3b2 has got me stumped; the "b2" means
> I added 2% copper to Glossy Base #3 (hence the "GB3"). It is not
> anywhere NEAR green. I fire electric (14hrs up to 1280C and soaking
> for 15 minutes, slow (18hrs) freefall cooling), so I really doubt I
> accidently made a copper red. Besides, the color is wrong for that,
> too. It is a - albeit beautiful - russet; a transparent reddish
> brown. I am stumped. The only other colorant I used that day for
> glaze tests was nickel - which can make a brown glaze, though I've
> never seen a nickel brown this nice; first time for everything I
> suppose. Also, the raw glaze REALLY looks like I added my
> blacker-than-sin copper oxide, rather than the black nickel oxide I
> use, which is black in name only (in fact it is a medium, vaguely
> greenish, gray).
>
> The recipe is (use at your own risk - this crazes on my body, and the
> transparent test had microbubbles suspended in it):
>
> 46 Neph. Sy.
> 44 Quartz
> 10 Calcite (natural calcium carb.)
> + (for suspension)
> 3 Bentonite Volclay (a sodium bentonite)
> 0.1 MgSO4 (Epsom salt)
>
> The unity for that (because I think I can pretty safely assume none of
> you have access to analyses for my materials) is:
>
> 0.45 CaO
> 0.04 MgO
> 0.11 K2O
> 0.40 Na2O
> 0.51 Al2O3
> 5.32 SiO2
> 0.03 Fe2O3
> 0.01 TiO2
>
> My clay body is a "white" stoneware, and fires greyish-white.
>
> Is there any way this could actually be produced by copper? If so,
> how to explain this result?
>
> Regards,
>
> Tim
Timothy Joko-Veltman on fri 15 aug 08
For the interested, here are some pix of the test tile in question:
http://www.joko-veltman.net/pix/mystery_copper_tile-back.jpg
http://www.joko-veltman.net/pix/mystery_copper_tile-front.jpg
Marian, your reply was very interesting and stimulating ... thank you very much.
Regards,
Tim
John Rodgers on fri 15 aug 08
My MC6 Floating Green calls for Chromium Oxide and Cobalt Oxide to
produce green. Same is true of Woloshyns Floating.
Something to consider
John Rodgers
Chelsea, AL
Timothy Joko-Veltman wrote:
> Took some glaze tests out of the kiln today. Some very nice and
> informative. The one marked GB3b2 has got me stumped; the "b2" means
> I added 2% copper to Glossy Base #3 (hence the "GB3"). It is not
> anywhere NEAR green. I fire electric (14hrs up to 1280C and soaking
> for 15 minutes, slow (18hrs) freefall cooling), so I really doubt I
> accidently made a copper red. Besides, the color is wrong for that,
> too. It is a - albeit beautiful - russet; a transparent reddish
> brown. I am stumped. The only other colorant I used that day for
> glaze tests was nickel - which can make a brown glaze, though I've
> never seen a nickel brown this nice; first time for everything I
> suppose. Also, the raw glaze REALLY looks like I added my
> blacker-than-sin copper oxide, rather than the black nickel oxide I
> use, which is black in name only (in fact it is a medium, vaguely
> greenish, gray).
>
> The recipe is (use at your own risk - this crazes on my body, and the
> transparent test had microbubbles suspended in it):
>
> 46 Neph. Sy.
> 44 Quartz
> 10 Calcite (natural calcium carb.)
> + (for suspension)
> 3 Bentonite Volclay (a sodium bentonite)
> 0.1 MgSO4 (Epsom salt)
>
> The unity for that (because I think I can pretty safely assume none of
> you have access to analyses for my materials) is:
>
> 0.45 CaO
> 0.04 MgO
> 0.11 K2O
> 0.40 Na2O
> 0.51 Al2O3
> 5.32 SiO2
> 0.03 Fe2O3
> 0.01 TiO2
>
> My clay body is a "white" stoneware, and fires greyish-white.
>
> Is there any way this could actually be produced by copper? If so,
> how to explain this result?
>
> Regards,
>
> Tim
>
>
>
Timothy Joko-Veltman on fri 15 aug 08
Thanks all for the input,
Angela ... I've asked all those questions, (except the second, because
I don't have any BIO, and manganese was not even taken off the shelf
that day). The other copper tests turned out as expected. And yes, I
know I'm going to have to do the test all over from scratch (but ran
out of quartz, so it'll have to wait, *sigh*). I'll be sure to bring
a witness when I do, make sure it's actually CuO I'm putting in the
glaze ...
Elizabeth ... the test tiles were at the bottom (farthest from the
flue), close only to iron- or cobalt-bearing glazes, and all near each
other - so the transparent version of the same glaze would show signs
of flashing, too ... but does not. Also, I don't even let Cr in the
studio door, much less the kiln door (I don't want my Glossy White
turning pink), and the coloration of the glaze is even all around, and
not indicative of flashing.
Regards,
Tim
Neon-Cat on fri 15 aug 08
Don't think you've lost your mind yet, Tim.
I was waiting for a call and got to messing around with the line spectra =
for copper, iron, calcium, and silica and correlating them to what we =
humans perceive as color and your glaze seems to fall right into an area =
where we humans would be seeing brown as the color of the glaze. This is =
if we pretend you have created a calcium, copper, iron silicate glaze of =
some sort. I included the iron from your glaze because it will also form =
part of the silica matrix and contribute to color perception.=20
Recall Egyptian Paste - it's a calcium copper silicate similar to the =
rare but natural mineral Cuprorivaite
[Ca,Cu]SiO4O10. According to "The Pigment Compendium: A Dictionary of =
Historical Pigments (2004)" we could create its vivid beautiful blue by =
mixing quartz, calcium carbonate, and copper oxide in a ratio of =
4SiO2:1CaO:1CuO and heating it to 900 -10000 C (1652 - 18320 F), then =
maintaining it at 8000 C (14720 F) for 10 - 100 hours. By comparison, =
your copper glaze ratio works out to about 39SiO2:3CaO:1CuO plus 0.1 =
iron. For a workable modern green Cone 10 glaze the ratio might be about =
55SiO2:10CaO:4CuO plus 0.1 iron. Your ratio is close to neither the good =
blue or green colored copper oxide glazes mentioned here, hence the =
brown color. You could try your glaze again using a higher percentage of =
copper oxide and see what happens. It might get you closer to green. =20
I'm the one probably out of my mind for fooling with line spectra ... =
but it is fun in an odd sort of way. I don't have the computer capacity =
or necessary programs to really run color predictions or evaluations =
from line spectra and glaze formula percentages (or the patience to work =
many more by hand) but the concept is intriguing.
Happy glazing!
Marian
www.neon-cat.com
Ivor and Olive Lewis on sat 16 aug 08
Dear Marian,
When the subject of Egyptian Blue was discussed a couple of years ago
I attempted to make this pigment without success using the
Stoichiometric blend. All I got was a black sintered mass. Not a hint
of Blue.
A search for pictures of Cuprorivaite turned up images which claimed
the crystals were about half a millimetre square.
From the way the mineral is described, it seems to be Wollastonite
with some Cu2+ substituted for Ca2+ with strong four fold coordination
to provide the colour centre.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Neon-Cat on sat 16 aug 08
Hello there Ivor and everyone else!
Glassy blue Cuprorivaite, CaCuSi4O10, is a layered phyllosilicate, a sheet
of 6-membered rings in 2:1 layers composed of tetragonal or pseudotetragonal
structures [Si4O10]4- and others (Group: P 4/nnc space-group symmetry).
According to The International Mineralogy Association (IMA), Cuprorivaite is
a valid mineral (Dana class 71.2.3, Cuprorivaite group) in the rather large
phyllosilicate group and has been for quite some time (1938). Its copper
content is essential to its nature. It is nothing like Wollastonite
(CaSiO3) which is not a phyllosilicate (Dana Class 65.2.1, Wollastonite
group -- all in this rather small group are triclinic inosilicates).
See Cuprorivaite's structure here under in the "Cuprorivaite
Crystallography": http://webmineral.com/data/Cuprorivaite.shtml
Ivor, I'm sorry your blue pigment experiment turned out yucky - bummer! As
someone once told me 'if you experiment you have to be willing to endure a
few heartaches'. In the real olden days Egyptian Blue pigment was prepared
by melting copper-rich ingredients like cuprite (Cu2O) or tenorite (CuO)
with lime and desert sand. Using flux-like plant materials helped early
technicians working within low melting temperature ranges, 742°C (1368° F)
or less. Maybe you can try plant ash fluxes next time, Ivor, and a lower
firing temperature...
Good luck! And have fun!
Let us hear back how it goes.
Marian
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of Ivor and Olive
Lewis
Sent: Saturday, August 16, 2008 1:47 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Am I out of my mind? (glaze-related)
Dear Marian,
When the subject of Egyptian Blue was discussed a couple of years ago
I attempted to make this pigment without success using the
Stoichiometric blend. All I got was a black sintered mass. Not a hint
of Blue.
A search for pictures of Cuprorivaite turned up images which claimed
the crystals were about half a millimetre square.
From the way the mineral is described, it seems to be Wollastonite
with some Cu2+ substituted for Ca2+ with strong four fold coordination
to provide the colour centre.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
| |
|
