Barbara Brown on fri 15 aug 03
I need to buy some cobalt oxide. Does anyone have a suggestion of what
pottery supply company has the best price?
Barbara
Barbara Brown phone/fax 408-736-3889
1225 Manzano Way,Sunnyvale,Ca. 94089
http://www.silverhawk.com/crafts/bbrown97
email: bbrown3@webtv.net
John Hesselberth on sat 16 aug 03
Hi Barbara,
I strongly recommend you buy from a reputable supplier you trust and
one that you want to stay in business. Shopping price on things like
cobalt has caused some of us grief in the past by getting low quality
material.
Regards, John
On Friday, August 15, 2003, at 08:42 PM, Barbara Brown wrote:
> I need to buy some cobalt oxide. Does anyone have a suggestion of what
> pottery supply company has the best price?
http://www.frogpondpottery.com
http://www.masteringglazes.com
Des & Jan Howard on sun 17 aug 03
Jacka
I'm not sure what you mean by "micro fine". All of the
cobalt carbonate we use comes impalpably fine & then
we ball mill the hell out of it along with any other
"non-rock" glaze additions. No crawling there.
We use a goodly quantity of CMC gum as a
glaze hardener, this slop stirred with a high speed drill attached
mixer does cause some annoying frothing, so, we tried
sugar as a glaze hardener. Bad move!
Three days of summer & 10 gallons of glaze became
15 gallons of froth with a vomitous odour.
Des
John K Dellow wrote:
> Also beware of micro fine cabalt carbonate. Will causes some glazes to
> crawl. This
> bloke just got caught :(. $60 of carbonate in a 10Liter batch which is
> useless. My friend
> Geoff Walker of Cronulla pottery here on the Gold Coast surgested
> adding sugar
> to the glaze slop . Any better surgestions ?.
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.hwy.com.au
Earl Krueger on sun 17 aug 03
John,
From your message I understand that you are blaming the particle size
of the cobalt carbonate for your crawling problem.
> Also beware of micro fine cabalt carbonate. Will causes some glazes to
> crawl.
Given the cost of cobalt compounds another interpretation could be that
the product has been adulterated. I did an experiment:
I added about 1/8 teaspoon of cobalt carbonate to about 2 tablespoons
of vinegar. After the fizzing stopped I had a clear smoky brown
solution with no sign of particles that didn't dissolve. Had there
been I would have suspected some form of contaminant. This is not
conclusive since the contaminant could also be soluble in vinegar.
Another test, which I haven't tried, would be to test for water soluble
components. You could try this by: 1: Dry some of your cobalt compound
in the oven at 200 F for about an hour.
2: Weigh the material on a sensitive balance.
3: Wash by dispersing in plain water, let settle and decant off the
clear liquid. Do this step at least twice.
4: Dry the powder again in your oven.
5: Weigh the material again.
If there was an appreciable loss in weight I would suspect a
contaminant. This would take some careful work so as to not give you
false results.
These test can not prove that you cobalt is pure but they could show
that it is contaminated.
If you find that your cobalt is contaminated I would certainly complain
to the supplier. Or, if you want to invest the time, you could try to
purify it. I found that I could precipitate out cobalt carbonate from
the cobalt acetate solution I made by adding sodium carbonate (washing
soda). Of course you would have to be sure to wash out all of the
sodium you are adding.
Good luck.
Just a novice at glazes but understand a little inorganic chemistry.
Earl...
John K Dellow on sun 17 aug 03
Also beware of micro fine cabalt carbonate. Will causes some glazes to
crawl. This
bloke just got caught :(. $60 of carbonate in a 10Liter batch which is
useless. My friend
Geoff Walker of Cronulla pottery here on the Gold Coast surgested
adding sugar
to the glaze slop . Any better surgestions ?.
John Hesselberth wrote:
> Hi Barbara,
>
> I strongly recommend you buy from a reputable supplier you trust and
> one that you want to stay in business. Shopping price on things like
> cobalt has caused some of us grief in the past by getting low quality
> material.
>
> Regards, John
>
> On Friday, August 15, 2003, at 08:42 PM, Barbara Brown wrote:
>
>> I need to buy some cobalt oxide. Does anyone have a suggestion of what
>> pottery supply company has the best price?
>
> http://www.frogpondpottery.com
> http://www.masteringglazes.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.
>
--
John Dellow "the flower pot man"
Home Page http://www.welcome.to/jkdellow
http://digitalfire.com/education/people/dellow/
John K Dellow on mon 18 aug 03
Thanks,Des,
I will try to mill like you said with my next batch.I
do not have any cmc,but will
buy and try. I needed to get some because I`d like to try some shino
glazes in the bourry.
John
Des & Jan Howard wrote:
>Jacka
>I'm not sure what you mean by "micro fine". All of the
>cobalt carbonate we use comes impalpably fine & then
>we ball mill the hell out of it along with any other
>"non-rock" glaze additions. No crawling there.
>
>We use a goodly quantity of CMC gum as a
>glaze hardener, this slop stirred with a high speed drill attached
>mixer does cause some annoying frothing, so, we tried
>sugar as a glaze hardener. Bad move!
>Three days of summer & 10 gallons of glaze became
>15 gallons of froth with a vomitous odour.
>
>Des
>
>
>John K Dellow wrote:
>
>
>
>>Also beware of micro fine cabalt carbonate. Will causes some glazes to
>>crawl. This
>>bloke just got caught :(. $60 of carbonate in a 10Liter batch which is
>>useless. My friend
>>Geoff Walker of Cronulla pottery here on the Gold Coast surgested
>>adding sugar
>>to the glaze slop . Any better surgestions ?.
>>
>>
>
>--
>
>Des & Jan Howard
>Lue Pottery
>LUE NSW 2850
>Australia
>Ph/Fax 02 6373 6419
>http://www.luepottery.hwy.com.au
>
>______________________________________________________________________________
>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.
>
>
>
--
John Dellow "the flower pot man"
Home Page http://www.welcome.to/jkdellow
http://digitalfire.com/education/people/dellow/
Des & Jan Howard on mon 18 aug 03
Jacka
Watch the pennies!
Buy the CMC gum as "legume pelleting adhesive" from your local rural supply shop.
Cheap as chips!
Des
John K Dellow wrote:
> Thanks,Des,
> I will try to mill like you said with my next batch.I
> do not have any cmc,but will
> buy and try. I needed to get some because I`d like to try some shino
> glazes in the bourry.
> John
>
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.hwy.com.au
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