Jeremy/Bonnie Hellman on sun 5 jan 97
Hello all,
I recently wanted to try a ^6 oxidation glaze recipe which called for
Copper Oxide. So I looked in my supplier's catalog to find that it comes
in Black and Red-- same price ($4.75/lb for under 5 lbs). I already owned
some copper carbonate which sells for $3.75/lb under 5 lbs.
I looked in my ceramics books to find that a substitute for copper oxide
is to use twice as much copper carbonate which has smaller particle size.
Has anyone experiemented with this? Sounds like the same conversion with
cobalt oxide and carbonate. However, if the oxide is twice as "strong" as
the carbonate, why not use the oxide more often, since it would be cost
effective? Yet, most of the ^6 Ox glaze recipes I seem to have selected
call for carbonate.
Then there is the question of color. I spoke with a friendly chemist (not
a potter) who told me that to create red copper oxide the mfg takes black
copper oxide and removes some oxygen to give a higher ratio of copper to
oxygen. (At least that's what I think she told me--I'm no
chemist-obviously.) That was interesting but it didn't explain why they
were sold at the same price and which one I probably wanted to use. I
ended up with black because that's what the technical person told me I
wanted for my green glazes in cone 6 oxidation.
Help and information would be appreciated! TIA
Bonnie in Pittsburgh, PA where we had an unseasonably warm day, allowing
glaze creation in an otherwise cold basement
"Outside a dog, a book is a man's best friend. Inside a dog, it's too
dark to read" Groucho Marx
" " Harpo Marx
"Time flies like an arrow. Fruit flies like an avocado" Att. to GM
Bruce Michaels on mon 6 jan 97
On Sun, 5 Jan 1997, Jeremy/Bonnie Hellman wrote:
> ----------------------------Original message----------------------------
> Hello all,
>
> I recently wanted to try a ^6 oxidation glaze recipe which called for
> Copper Oxide. So I looked in my supplier's catalog to find that it comes
> in Black and Red-- same price ($4.75/lb for under 5 lbs). I already owned
> some copper carbonate which sells for $3.75/lb under 5 lbs.
>
> I looked in my ceramics books to find that a substitute for copper oxide
> is to use twice as much copper carbonate which has smaller particle size.
I don't have any experience using one more then the other but if you just
go by molelecular weight you need 1.5 times as much copper carbonate when
you substitute for copper oxide. In other words if you need 80 grams of
copper oxide in a formula and you want to substitute copper carbonate you
will need 124 grams of it.
Bruce Michaels
David Hewitt on tue 7 jan 97
The oxide ores are tenorite and cuprite ( there are many other workable
copper ores - over ten I understand). Tenorite (CuO) is cupric oxide
and is black. Cuprite (Cu2O) is cuprous oxide and is a deep red colour
Copper Carbonate (CuCO3) is pale green and the basic carbonate
(CuCo3.Cu(OH)2) a deeper green.
Black copper oxide is a strong stain and tends to give a speckled colour
in all but the most runny glazes. Copper carbonate may be used in place
of copper oxide to avoid this speckle and give a more uniform colour.
Copper carbonate is not as strong as copper oxide and so you need 1.5
times as much by weight to give the same strength of colour.
In message , Jeremy/Bonnie Hellman writes
>----------------------------Original message----------------------------
>Hello all,
>
>I recently wanted to try a ^6 oxidation glaze recipe which called for
>Copper Oxide. So I looked in my supplier's catalog to find that it comes
>in Black and Red-- same price ($4.75/lb for under 5 lbs). I already owned
>some copper carbonate which sells for $3.75/lb under 5 lbs.
>
>I looked in my ceramics books to find that a substitute for copper oxide
>is to use twice as much copper carbonate which has smaller particle size.
>Has anyone experiemented with this? Sounds like the same conversion with
>cobalt oxide and carbonate. However, if the oxide is twice as "strong" as
>the carbonate, why not use the oxide more often, since it would be cost
>effective? Yet, most of the ^6 Ox glaze recipes I seem to have selected
>call for carbonate.
>
>Then there is the question of color. I spoke with a friendly chemist (not
>a potter) who told me that to create red copper oxide the mfg takes black
>copper oxide and removes some oxygen to give a higher ratio of copper to
>oxygen. (At least that's what I think she told me--I'm no
>chemist-obviously.) That was interesting but it didn't explain why they
>were sold at the same price and which one I probably wanted to use. I
>ended up with black because that's what the technical person told me I
>wanted for my green glazes in cone 6 oxidation.
>
>Help and information would be appreciated! TIA
David Hewitt
David Hewitt Pottery Caerleon, Tel:- 01633 420647
7 Fairfield Road, Caerleon, Newport, South Wales, UK.
URL http://digitalfire.com/magic/hewitt.htm
Omer Artun on wed 15 jan 97
1 % cobalt oxide is not 2 % cobalt carbonate.
To Calculate the equivalent amount needed one needs to look up atomic
weights from the periodic table.
The atomic weight is the weight of the element if one weighed
exactly 6.022 10^23 of them on a scale ( which is called one mole)
Element Atomic Weight (gr/mole)
----------------------------------------------------
Cu (copper) 63.55
Co (cobalt) 58.93
Fe (iron) 55.85
C (carbon) 12.01
O (Oxygen) 15.999
Now the formula for Copper oxide is Cu O and cooper carbonate is
2
Cu CO .
2 3
One mole of copper oxide weighs: 2*63.55+16= 143 gr percentage of copper
in this oxide is ( % copper= 127/143) 89 %, this means that if we use
100 gr of this material we introduce 89 gr of copper into the mixture.
Now same for Copper carbonate,
One mole of copper carbonate weighs : 2*63.55+12+3*16=187 gr. percentage
of copper in this carrbonate is (% copper = 127/187) 68 %
Now the conversion is between the percentages
Copper Oxide/CopperCarb = 89/68=1.31
meaning that istead of 1 % copper oxide you need to use 1.3 % copper
carbonate .
This is an example how you can calculate the conversion. The formulas
might be actually different. I am just giving this example to show you
how to calculate it. In a previous posting I have seen that Copper
carbonate is not actually CuCO3 but some other combined hydroxil group
copper. But if you get the molecular formula from the supplier, you can
convewrt percentages by using the above method.
Good luck,
OMER BERAT ARTUN
------------------------------------------------------------------------
Institute for Brain and tel: 401 421 2879 (home)
Neural Systems, 401 863 3920 (office)
Department of Physics 401 863 3494 (fax)
Box 1843
Brown University URL: http://www.physics.brown.edu/people/artun
Providence RI 02912 e-mail: artun@cns.brown.edu
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