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CuO (Cupric Oxide)

Family	Colorant
Weight	79.540

MLPT - Melting Point (MP)

1336C (From The Oxide Handbook)

Notes

-Copper can be produced from many different raw materials, the main being black tenorite (CuO), deep red cuprite (Cu2O), bright green malachite (CuCO3.Cu(OH)2), and bright blue azurite (2CuCO3.Cu(OH)2).

-Under normal oxidizing conditions the CuO molecule remains unchanged and produces clear green colors in glazes. Copper is a strong flux and even 2% can considerably increase the melt fluidity of a glaze.

-CaO is unlikely to affect the color of copper in a glaze.

-Copper is well-known for its ability to produce blood-red and fire-red colors in reduction atmosphere firings where it is altered to Cu2O (see Cu2O).

-Purple copper reduction glazes are the result of a mixture of copper in its green oxidized and red reduced forms. This effect appears most frequently in high lime glazes or where early stages of firing are oxidizing or latter stages are light or neutral.

-The shade of copper greens can vary with firing rate and soaking changes. The best colors are generally obtained with fast firing and little soaking.

-Copper is an active flux and may increase melt fluidity and may increase crazing because of its high thermal expansion.

-Crystalline glazes can be attractive when done with copper.

-In the enameling industry, copper is used in combination with small quantities of cobalt, manganese, or nickel in making black where the black is produced in the smelter.

-Copper and titanium can produce beautiful blotching and specking effects. Pure copper metal filings can make an extremely potent specking material in reduction firing for both bodies and glazes.

-Generally additions of copper to a glaze will reduce crazing (if supplied in adequate amounts; beyond 1 or 2 percent).

Note: When added to low lead solubility glazes copper can cause the solubility of the lead to be greatly increased. Copper can have similar effects in other types of glazes at other temperatures also. If an overnight soak in vinegar or acid changes glaze appearance, be careful.

Mechanisms

Glaze Color - Metallic Green
7% copper in glossy oxidation glazes can produce striking metallic green colors.
Glaze Color - Green
Under normal oxidizing conditions CuO produces clear green colors in most glazes. The shade of green depends not only on the amount but also on other oxides present (i.e. lead in larger amounts will enhance and darken the green, the presence of alkalies or high boron will shift it toward blue).
Copper in calcium/magnesium glazes gives a green very different from that produced with lead.
Glaze Color - Turquoise, Blue-green
Combinations of CuO with tin or zircon will give turquoise or blue-greens when the glaze is alkaline (KNaO) and low alumina. Look for a frit with this profile for best results. Glazes of this type often craze.
Glaze Color - Green Yellowish
K2O can turn a copper glaze yellowish. If Na2O or PbO are present, K2O should not exceed 0.15 equivalent.
Glaze Color - Blue
Copper in a barium/zinc/sodium glaze gives a blue. Color can also be enhanced by
lithia.
Tin and copper can produce turquoise to robin's egg blue.

Out Bound Links

(Materials - Closest material equivalent) Copper Oxide Black - CuO
Copper (II) Oxide, Black Copper, BCO, Cupric Oxide
(Materials - Material source) Copper Oxide Red - Cu2O
Cu2O, Red Copper, RCO, Copper (I) Oxide, Cuprous Oxide
(Materials - Material source) Stain
Ceramic Stains

Pictures
Copper oxide (2%) added to an otherwise stable cone 6 glaze fluxes it considerably

Copper red shows the importance of correct firing (inside is red, outside is grey)

Metallic oxides with 50% Ferro frit 3134 in crucibles at cone 6ox. Chrome and rutile have not melted, copper and cobalt are extremely active melters. Cobalt and copper have crystallized during cooling, manganese has formed an iridescent glass.

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