{{nofootnotes, date=November 2010Ceramic colorants are added to a glaze or a clay to create color.

Carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...

s and

oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...

s of certain metals, characterize most colorants including the commonly used

cobalt carbonate Cobalt(II) carbonate is the inorganic compound with the formula CoCO3. This reddish paramagnetic solid is an intermediate in the hydrometallurgical purification of cobalt from its ores. It is an inorganic pigment, and a precursor to catalysts. ...

cobalt oxide Cobalt oxide is a family of chemical compounds consisting of cobalt and oxygen atoms. Compounds in the cobalt oxide family include: * Cobalt(II) oxide (cobaltous oxide), CoO *Cobalt(III) oxide Cobalt(III) oxide is the inorganic compound with the ...

, chrome oxide,

red iron oxide Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturall ...

, and

copper carbonate Copper carbonate may refer to : ;Copper (II) compounds and minerals * Copper(II) carbonate proper, (neutral copper carbonate): a rarely seen moisture-sensitive compound. * Basic copper carbonate (the "copper carbonate" of commerce), actually a cop ...

. These colorants can create a multitude of colors depending on other materials they interact with and to which temperature and in which atmosphere they are fired.

Cobalt

Cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...

is commonly used in either its carbonate (CoCO₃) or its oxide (Co₃O₄) forms. In the presence of most fluxes, it yields blue colors ranging from low saturation pastels to high saturation midnight blues in both oxidation and reduction atmospheres. However, in the presence of magnesium, cobalt can become purple or pink depending on whether it was fired in oxidation (yields purple) or reduction. Cobalt is also commonly used in black glazes and in washes as decorative medium. Common saturation percentages for low saturation range from (.25 to .5%) and in high saturation from (1 to 2%).

Chrome

"Chrome is a rather versatile and fickle colorant," (Chappell). Chrome oxide (Cr₂O₃) is commonly used for achieving greens. However, in the presence of zinc, chrome can produce brown. Glazes with tin oxide present will often blush to pink if fumed with chrome or if chrome is present in the glaze with the tin, often intense pinks occur. If fired above cone 6, chrome will fume and become a gas in the kiln. Common saturation percentages for chrome at low saturation range from (.25 to .5%) and at higher percentages from (1 to 2%). Chrome is a refractory.

Red Iron

Iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

is commonly used as a colorant in its red iron oxide form as (Fe₂O₃). Red iron oxide is commonly used to produce earthy reds and browns. It is the metal responsible for making earthenwares red. Iron is also another tricky colorant because of its ability to yield different colors under different circumstances. At low percentages (.5-1%) and in the presence of potassium, iron will become light blue or light blue-green in reduction (as is seen in traditional celadons). In the presence of barium, iron may become yellow green. When used in combination with calcium, red iron oxide can become pale yellow or amber in oxidation or green in reduction. Common percentages for red iron oxide range from (4 up to 10%).

Copper

Copper's carbonate form (CuCO₃) is commonly used to produce greens, turquoise, and copper reds. If need be, copper oxide (CuO) can be substituted but has a larger particle size and glazes should be adjusted to generally half the amount called for. In barium based glazes greenish blues often result from copper. Alkaline

feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feldsp ...

glazes with copper fired in reduction atmospheres will often yield ox blood or copper red glazes discovered by the Chinese. When fired above cone 8 copper can become unstable and will often fume off of a glaze in vapor form.

References

*''Clay and Glazes: Revised edition''. Chappell, James. Watson-Guptill Publications, New York. 1991. *''Glazes for the Craft Potter''. Fraser, Harry. Watson Guptill Publications, New York. 1974. *''Clay and Glaze for the Potter''. Rhodes, Daniel. Krause Publications. 2000. Expanded and Revised by Robin Hopper. Ceramic materials