Earl Brunner on mon 12 jun 06
The last batch of cobalt oxide that we purchased from
Aardvark does this, I use the oxide for a speckled blue
and the carbonate for a smooth blue. What I don't know
is how long ago we bought this stuff and if the current
stuff will have the specks.
Earl Brunner
Las Vegas, NV
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On
Behalf Of Ron Roy
Sent: Monday, June 12, 2006 12:03 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Cobalt with specks
Does anyone have or know where to get some cobalt that
has enough larger
particles to produce specking - someone has asked me
where to get some and
I don't know.
Here is their address in case anyone would care to
respond.
"Michael & Frances Morris"
RR
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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clennell on mon 12 jun 06
Sour Cherry Pottery
> Does anyone have or know where to get some cobalt that has enough larger
> particles to produce specking - someone has asked me where to get some and
> I don't know.
>
> Here is their address in case anyone would care to respond.
>
> "Michael & Frances Morris"
>
> RR
>
>
RR: Usually cobalt with specking is just a case of using cobalt oxide versus
cobalt carbonate. I usually use carbonate for a glaze to avoid specking. the
oxide needs to be put thru a 100 mesh screen a few time it seems to avoid
the specking. this is probably what this person wants.
Hope this helps.
Tc
Tony and Sheila Clennell
Sour Cherry Pottery
4545 King Street
Beamsville, Ontario
CANADA L0R 1B1
http://www.sourcherrypottery.com
Ron Roy on mon 12 jun 06
Does anyone have or know where to get some cobalt that has enough larger
particles to produce specking - someone has asked me where to get some and
I don't know.
Here is their address in case anyone would care to respond.
"Michael & Frances Morris"
RR
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Bob Masta on tue 13 jun 06
Hamer and Hamer suggests that "A deliberate
speckle is easily obtained by adding the cobalt
oxide to the already sieved glaze and stirring it in
without further sieving." They go on to mention
that to avoid speckle you normally have to grind
the color with part of the glaze and sieve twice
at 120 mesh.
I have found with cobalt aluminate stain, without
the above grinding and double-sieving, that
speckle seems to be the norm. However, I
can't compare with other forms of cobalt:
I got a pound of the stain as a gift, and at
the price of cobalt I'm not going to worry if
another form is more soluble!
Best regards,
Bob Masta
-------------------------------------
> Date: Mon, 12 Jun 2006 14:02:58 -0500
> From: Ron Roy
> Subject: Cobalt with specks
>
> Does anyone have or know where to get some cobalt that has
> enough larger
> particles to produce specking - someone has asked me where
> to get some and
> I don't know.
Chuck Wagoner on tue 13 jun 06
I have some cobalt oxide that I purchased from American Art Clay that
speckles some, but I screen the glaze after adding it and most of the
"spots" seem to go away. In the glaze I wanted to speckle I added the
colorant after I had screened the base. You might want to consider how
safe the larger spots are for food use since they must be more
concentrated in those areas. I only used mine on non-food surface.
Chuck in Rockville, IN, where the three kinds of Bamboo in my yard ARE
out of control.
> Does anyone have or know where to get some cobalt that has enough
larger
> particles to produce specking
Heloisa Nunes on wed 14 jun 06
I wonder if it really depends on where the chemical comes from.
I just mixed a batch of clear glaze with cobalt carbonate and got spleckes
all over ( I bough as carbonate and it is purple as a carbonate not black as
cobalt oxide). I liked it but was wondering if I had to grind it or sieve
through a smaller mesh to get an even blue glaze...
Heloisa Nunes,
São Paulo, Brazil
Joe Brecha on wed 14 jun 06
We have occasionally gotten over size cobalt from our suppliers. Most =
recently an importer from China did not specifically request screening =
and the stuff was full of specks. We got rid of it as soon as we could. =
There must be some of that batch floating around out there. Our glaze =
tech kept some for personal use. We don't have any for sale, but ask =
around and see if any other suppliers still have some inventory. There =
is a company that actually makes color specs for industry. If I =
remember right they did not keep any inventory, but made each item when =
requested. I could see someone actually mixing some cobalt with a =
little flux, firing untill crunchy hard, and then grinding and screening =
the material to the size needed. Joe Brecha Clay Art Center
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