Al2O3 | B2O3 | BaO | C | CaO | CO2 | CoO | Cr2O3 | Cu2O | CuO | Fe2O3 | FeO | H2O | K2O | Li2O | LOI | MgO | MnO | MnO2 | Na2O | NiO | O | Organics | P2O5 | PbO | SiO2 | SnO2 | SO3 | SO4 | SrO | TiO2 | V2O5 | ZnO | ZrO | ZrO2Others
Ag2O | AlF3 | As2O3 | As4O6 | Au2O3 | BaF2 | BeO | Bi2O3 | CaF2 | CdO | CeO2 | Cl | CO | CrO3 | Cs2O | CuCO3 | Dy2O3 | Er2O3 | Eu2O3 | F | Fr2O | Free SiO2 | Ga2O3 | GdO3 | GeO2 | HfO2 | HgO | Ho2O3 | In2O3 | IrO2 | KF | KNaO | La2O3 | Lu2O3 | Mn2O3 | MoO3 | N2O5 | NaF | Nb2O5 | Nd2O3 | Ni2O3 | OsO2 | Pa2O5 | PbF2 | PdO | PmO3 | PO4 | Pr2O3 | PrO2 | PtO2 | RaO | Rb2O | Re2O7 | RhO3 | RuO2 | Sb2O3 | Sb2O5 | Sc2O3 | Se | SeO2 | Sm2O3 | Ta2O5 | Tb2O3 | Tc2O7 | ThO2 | Tl2O | Tm2O3 | U3O8 | UO2 | WO3 | Y2O3 | Yb2O3
|GSPT - Frit Softening Point||1336C (From The Oxide Handbook)|
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
Tin and copper can produce turquoise to robin's egg blue.
Copper oxide (2%) added to an otherwise stable cone 6 glaze fluxes it considerably
The Copper Red effect shows the importance of correct firing to achieve a specific effect with certain glaze recipes. The inside of this vase was more heavily and consistently reduced, simply because it was isolated somewhat from the outside kiln atmosphere. The outside of the vase, by contrast, is grey (a product of periods of oxidation during the firing).
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.
A closeup of a glossy Cone 6 glaze having 4% added copper carbonate. The bottom section has leached in lemon juice after 24 hours. This photo has been adjusted to spread the color gamut to highlight the difference. The leached section is now matte.
All common traditional ceramic base glazes are made from only a dozen elements (plus oxygen). Materials decompose when glazes melt, sourcing these elements in oxide form. The kiln builds the glaze from these, it does not care what material sources what oxide (assuming, of course, that all materials do melt or dissolve completely into the melt to release those oxides). Each of these oxides contributes specific properties to the glass. So, you can look at a formula and make a good prediction of the properties of the fired glaze. And know what specific oxide to increase or decrease to move a property in a given direction (e.g. melting behavior, hardness, durability, thermal expansion, color, gloss, crystallization). And know about how they interact (affecting each other). This is powerful. And it is simpler than looking at glazes as recipes of hundreds of different materials (each sources multiple oxides so adjusting it affects multiple properties).
These are four cone 6 glazes of diverse chemistry. They have varying melt fluidities. They are soaked (half way up) in lemon juice over night. None show any evidence of surface changes. All contain 2% copper carbonate. If the copper was increased, especially to the point of going metallic or crystallizing, likely the leaching test would have different results. So, if you use copper sensibly (in moderate amounts), there is a good chance you can make a glaze that resists leaching.
Out Bound Links
Copper (II) Oxide, Black Copper Oxide, BCO, Cupric Oxide
Cu2O, Red Copper, RCO, Copper (I) Oxide, Cuprous Oxide
By Tony Hansen