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## cobalt oxide vs cobalt carbonate

### tgschs10 on thu 11 may 00

-------------------
I was mixing a glaze today that called for cobalt oxide=3B instead I added =
cobalt
carbonate. Is there anything I can do=3B I have a feeling there not =
equivalent?
Thanks
Tom Sawyer
tgschs10=40msn.com

### sibylle on fri 12 may 00

Dear Tom,

some time ago there was a calculation about substitution of cobalt carbonate and
cobalt oxide from "smart" given to this list. If you missed it, here I post it f
you. Perhaps you can simply add the missing parts of cobalt carbonate.

1) For Cobalt :
100 g of Cobalt oxide (Co3O4) gives 96,57 g of CoO (Cobalt basic oxide)
100 g of Cobalt carbonate (CoCO3) gives 63 g of CoO (Cobalt basic oxide)
Cobalt basic oxyde is what you need in your glaze.
So you can substitute 1 part of Cobalt oxide by 1,53 part of Cobalt carbonate
and if you reverse the calculation,
You can substitute 1 part of Cobalt carbonate by 0,653 part of Cobalt oxide.

Hope this helps

Sibylle

> ----------------------------Original message----------------------------
> -------------------
> I was mixing a glaze today that called for cobalt oxide; instead I added cobal
> carbonate. Is there anything I can do; I have a feeling there not equivalent?
> Thanks
> Tom Sawyer
> tgschs10@msn.com

### Lois Ruben Aronow on fri 12 may 00

------------------
On Thu, 11 May 2000 16:51:13 EDT, you wrote:

=3E----------------------------Original message----------------------------
=3E-------------------
=3EI was mixing a glaze today that called for cobalt oxide=3B instead I =
=3Ecarbonate. Is there anything I can do=3B I have a feeling there not =
equivalent?

They're not. The general rule of thumb is to use 2x as much carb as
oxide. So if your recipe called for 4=25 cobalt ox, and you used 4=25
cobalt carb, then add another 4=25 of the carb. Should be close to
equivalent.

Or just test it as is and see what comes out - it could be nice=21

### WHew536674@cs.com on fri 12 may 00

Tom,
If a glaze calls for 5 grams of cobalt ox, and you use cobalt carb, divide
the amount of 5 in half, that would give you 2.5 and add that amount to the
carb, giving you 7.5 and that is how much you would use. For 3 grams of Ox,
you would use 4.5 of carb, etc.
Joyce A.
Mission, TX

### Cindy Strnad on fri 12 may 00

Hi, Tom.

Someone will no doubt give you a more exact equivalent, but when I'm short
on one or the other, I substitute cobalt oxide:cobalt carbonate in a 1:2
ratio. You might want to try a glaze sample of your cobalt carbonate glaze
first, though. Who knows? It may be just as, or prettier than the original
glaze.

earthenv@gwtc.net
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730

### Hank Murrow on fri 12 may 00

>I was mixing a glaze today that called for cobalt oxide; instead I added
>cobalt
>carbonate. Is there anything I can do; I have a feeling there not equivalent?
>Thanks
>Tom Sawyer
>tgschs10@msn.com

Great Tom! You now have the chance to see what the glaze looks like with
less Co in it than called for. Fire it as is; and add more if you prefer it
deeper colored. It is the CO2 which burns out of the CoCO3, thus you need
to make up this weight to equal the same Co content as CoOxide. Let us
know, Hank in Eugene

### Anne POSSOZ on fri 12 may 00

> ----------------------------Original message----------------------------
> I was mixing a glaze today that called for cobalt oxide; instead I added cobal
> carbonate. Is there anything I can do; I have a feeling there not equivalent?
> Tom Sawyer

The molar mass of CoO is 74.933 and the one of CoCO3 is 118.94.
Therfore, if you want the same final quantity of Cobalt oxide
in you glaze you should put 118.94/74.933 = 1.59 more of cobalt
carbonate than you would have put of cobalt oxide.

Anne

### Sharon31 on fri 12 may 00

Hello Tom!
The carbonate is weaker. The oxide particles are biggers, better for glazes
that needs "unsmooth" coloring.
Ababi
sharon@shoval.org.il
http://www.israelceramics.org/main.asp?what=gallery.htm
http://www.milkywayceramics.com/cgallery/asharon.htm
----- Original Message -----
From: tgschs10
To:
Sent: Thursday, May 11, 2000 11:51
Subject: Cobalt oxide vs cobalt carbonate

----------------------------Original message----------------------------
-------------------
I was mixing a glaze today that called for cobalt oxide; instead I added
cobalt
carbonate. Is there anything I can do; I have a feeling there not
equivalent?
Thanks
Tom Sawyer
tgschs10@msn.com

### Steve Slatin on fri 24 jun 05

Michael --

2/3 as much oxide as the recipe calls for carbonate is
real close. The oxide has a slightly lower LOI; that
should actually be an improvement for most glazes, and
typically a different granule size, but the
differences might not make much of a difference. And
at 2/3, you'll get the very similar depth of blue and
other characteristics.

-- Steve Slatin

--- Michael Juengling wrote:

> I would like to substitute Cobalt Oxide (which I
> have) for Cobalt
> Carbonate

Steve Slatin --

Frail my heart apart and play me little Shady Grove
Ring the bells of Rhymney till they ring inside my head forever

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### Michael Juengling on fri 24 jun 05

I would like to substitute Cobalt Oxide (which I have) for Cobalt
Carbonate (which I would have to buy) in a recipe. Is there any problem
doing this? What rate would I replace the Carbonate with the Oxide?
Thanks for any help.
Michael Juengling

### Mike Gordon on fri 24 jun 05

Michael,
Why don't you take a test batch of your base glaze and add 1/4 of 1% of
each form of cobalt to the batch and fire them side by side? You will
see for yourself what the difference is and it will be a whole lot more
meaningful for you to actually see the glaze instead of reading lots of
suggestions from the experts. In the end you will have to run tests
anyway. Good Luck, Mike Gordon
On Jun 24, 2005, at 5:15 AM, Michael Juengling wrote:

> I would like to substitute Cobalt Oxide (which I have) for Cobalt
> Carbonate (which I would have to buy) in a recipe. Is there any
> problem
> doing this? What rate would I replace the Carbonate with the Oxide?
> Thanks for any help.
> Michael Juengling
>
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### Earl Brunner on fri 24 jun 05

Someone else hopefully will give you the conversion, but one of the problems (not necessarily a problem) is that the cobalt oxide we have at the art center seems to be a little coarser than the carbonate. When I use it instead of the carbonate, the light blue glaze has nice blue speckles in it. I could probably eliminate them by screening, but they like the speckles so we do it intentionally.

Michael Juengling wrote:I would like to substitute Cobalt Oxide (which I have) for Cobalt
Carbonate (which I would have to buy) in a recipe. Is there any problem
doing this? What rate would I replace the Carbonate with the Oxide?
Thanks for any help.
Michael Juengling

______________________________________________________________________________
Send postings to clayart@lsv.ceramics.org

You may look at the archives for the list or change your subscription
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Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.

Earl Brunner
e-mail: brunv53@yahoo.com

### Snail Scott on sat 25 jun 05

At 08:15 AM 6/24/2005 -0400, you wrote:
>I would like to substitute Cobalt Oxide (which I have) for Cobalt
>Carbonate. What rate would I replace the Carbonate with the Oxide?

Use half as much. It can be prone to speckling
and it's tougher to measure very low percentages
accurately, but it will work.

-Snail