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## converting red copper oxide

### Charles Moore on wed 3 jul 02

----- Original Message -----=20
From: Charles Moore=20
To: Ceramic Arts Discussion List=20
Cc: Charles Moore=20
Sent: Tuesday, July 02, 2002 5:10 PM
Subject: Converting Red Copper Oxide

Clayarters,

This may be a repeat message. If so, please excuse. I earlier sent the =
same message, found a typo in percentage, and asked Mel to delete my =
message. Then I sent a corrected version that has not yet appeared.

In the recent July/August issue of Clay Times, I found a recipe, Dixon's =
Matte Green, ^6 Ox (p. 51). The recipe calls for 1.9% of "Red Copper =
Oxide."

Though I am not sure I want to try the recipe, I would like to know how =
to make the conversion from Red Copper Oxide to Copper Carbonate, which =
I am accustomed to using.

According the Hamer and Hamer in "A Potter's Dictionary, 4th edition (p, =
76), the CF's (Conversion Factors) for copper oxides are as follows:
Black copper oxide (CuO): the CF is 1.0 "because all the material =
enters the fusion as CuO.
Red copper oxide (Cu2O): the CF is 1.11 "because this takes up oxygen =
during firing to increase its bulk and becomes CuO to enter the =
fusion."
Copper carbonate (CuCO2): the CF is .645 (i.e., less than 1.0) "because =
there is a loss of carbon dioxide during firing."

Further: "To convert a copper oxide amount in a recipe to a copper =
carbonate amount, multiply by 1.55" (p. 75). This statement does not =
specify Red or Black Copper Oxide. I think that the conversion here =
refers to Black Copper Oxide. =20

How do we convert Red Copper Oxide to Copper Carbonate? I assume that =
since the Red Copper Oxide is stonger than Black by a factor of + 0.11, =
there might be a significant difference.

You chemistry dunce,

Charles Moore
Sacramento

### John Hesselberth on wed 3 jul 02

On Wednesday, July 3, 2002, at 03:10 PM, Charles Moore wrote:
>
>
> How do we convert Red Copper Oxide to Copper Carbonate? I assume that
> since the Red Copper Oxide is stonger than Black by a factor of + 0.11,
> there might be a significant difference.
>
> You chemistry dunce,
>
> Charles Moore
> Sacramento
>

Hi Charles,

The first thing you have to realize in doing this conversion is that
what we buy as copper carbonate usually is the mineral malachite. Its
formula is Cu(OH)2.CuCO3. The conversion factors I use are that 5%
"copper carbonate" = 3.6% black copper oxide = 3.24% red copper oxide.
That means to convert red copper oxide to copper carbonate you multiply
by 1.54--about the same as the 1.55 you quoted.

Another point to make is that red copper oxide is extremely difficult to
disperse well in a glaze slurry. You have to use soap or some other
wetting agent to get it well dispersed. I always stick with copper
carbonate for that reason alone.

Regards,

John