Paul Lewing on mon 24 may 04
on 5/24/04 5:53 AM, Hank Murrow at hmurrow@EFN.ORG wrote:
> You will succeed in developing this color from cobalt if you
> concentrate on glazes which have a large content of Magnesia, from any
> source. It will further succeed if you develop mat glazes with an
> excess of flux, shiny glazes will not produce this color well.
Hank is correct about all of that. I would add that lithium and barium will
promote this color from cobalt and magnesia, zinc, sodium, and potassium
will not.
Paul Lewing, Seattle
May Luk on mon 24 may 04
Hi All;
In my glaze group, we are investigating a glaze effect; some sort of cobalt
colour with pink speck. We'd like to know what colourant that caused the
effect and the glaze condition that promotes it.
Cone 6-9 Oxidation is our firing range. It doesn't matter if it's glossy or
matte. We are going to test.
Also, is there a ceramic supply store in San Jose, California? Am looking
for Talc analysis from that supplier.
Thanks
May
London, UK
John Kudlacek on mon 24 may 04
Hi May, (How timely.)
The glaze you mention is likely to be a magnesia glaze colored
with cobalt. I would try cobalt oxide as opposed to cobalt carbonate as
the oxide is coarser and would encourage speckling. Rhodes says, " colors
(colour) of this kind occur within a narrow range of temperatures and
atmosphere".
John in Topeka, U.S.A.
Hank Murrow on mon 24 may 04
Dear May Luk;
You will succeed in developing this color from cobalt if you
concentrate on glazes which have a large content of Magnesia, from any
source. It will further succeed if you develop mat glazes with an
excess of flux, shiny glazes will not produce this color well. In
addition, a soak in oxidation during the cooling at around 1800F will
help the color.
Cheers, Hank in Far Hills NJ today, resting from a wonderful workshop
with the great potters that share a love of clay with Marvin
Flowerman......my host.
On May 24, 2004, at 4:57 AM, May Luk wrote:
>
> In my glaze group, we are investigating a glaze effect; some sort of
> cobalt
> colour with pink speck. We'd like to know what colourant that caused
> the
> effect and the glaze condition that promotes it.
>
> Cone 6-9 Oxidation is our firing range. It doesn't matter if it's
> glossy or
> matte. We are going to test.
Wes Rolley on mon 24 may 04
At 09:57 AM 5/24/04 +0100, you wrote:
>Also, is there a ceramic supply store in San Jose, California? Am looking
>for Talc analysis from that supplier.
There was, for a long time, a store/manufacturer in San Jose called=20
"Claymaker". It recently sold and is now called "Clay Planet". They still=
=20
have the Web Site, http://www.claymaker.com/
"I find I have a great lot to learn =96 or unlearn. I seem to know far too=
=20
much and this knowledge obscures the really significant facts, but I am=20
getting on." -- Charles Rennie Mackintosh
Wesley C. Rolley
17211 Quail Court
Morgan Hill, CA 95037
(408)778-3024
June Perry on mon 24 may 04
As has been mentioned, the cobalt in a high magnesia glaze can give you
purple and the addition of tin can add those pink tones. You might try somewhere
between 2 and 5 % tin depending on how opaque you want the glaze to be.
Warm regards,
June Perry
http://www.angelfire.com/art2/shambhalapottery/
Alisa Liskin Clausen on tue 25 may 04
On Mon, 24 May 2004 09:57:31 +0100, May Luk
wrote:
>Hi All;
>
>In my glaze group, we are investigating a glaze effect; some sort of cobalt
>colour with pink speck. We'd like to know what colourant that caused the
>effect and the glaze condition that promotes it.
>
>Cone 6-9 Oxidation is our firing range. It doesn't matter if it's glossy or
>matte. We are going to test.
>
>
Dear May,
When I was trying to get a cobalt green, I found that a base with Dolomite
(magnesium) will produce a blue or grey blue, with lavendar or pink
speckling. I use my cone 6 Wodo White, which is
50 Neph. Sye
25 Dolomite
5.8 Wolalstonite
20 Ball Clay
ADD
1 Colbalt oxide
1 Tin Oxide
I have tried the same colorants in dolomite bases, with more or less
lavender blues as a result. Using Ball Clay instead of Kaolin, if that is
a posibility, could give you better color response and a better melt at
cone 6, due to the added magnesium and fluxes, in the Ball Clay. Lately I
have done some experiments in this vein, which started by simple error.
But I am beginning to see some surface differences I prefer with Ball Clay
instead of Kaolin.
regards from Alisa
Ron Roy on thu 27 may 04
Hi May, Hi Alisa,
When I look at this glaze as a Seger formula I see all the fluxes within
suggested limits - in other words - the MgO is high but not way high.
The other significant detail is - the silica is way low - as it usually is
in a clay matte glaze.
RR
The question becomes - is it necessary to have low silica to get the specking?
>Dear May,
>When I was trying to get a cobalt green, I found that a base with Dolomite
>(magnesium) will produce a blue or grey blue, with lavendar or pink
>speckling. I use my cone 6 Wodo White, which is
>50 Neph. Sye
>25 Dolomite
>5.8 Wolalstonite
>20 Ball Clay
>
>ADD
>1 Colbalt oxide
>1 Tin Oxide
>
>I have tried the same colorants in dolomite bases, with more or less
>lavender blues as a result. Using Ball Clay instead of Kaolin, if that is
>a posibility, could give you better color response and a better melt at
>cone 6, due to the added magnesium and fluxes, in the Ball Clay. Lately I
>have done some experiments in this vein, which started by simple error.
>But I am beginning to see some surface differences I prefer with Ball Clay
>instead of Kaolin.
>
>
>regards from Alisa
>
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Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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