CoO

CREATED:
MODIFIED:	1997.08.14
Family:	6 COLORANT
Raw Weight:	74.920
Fusion:	2860.00

Notes

Cobalt Oxide
(Sources: Cobalt Oxide)

-Cobalt is a trace element in vegetables and an important vitamin (B12) in stock raising. Cobalt metal is used in steel and chrome alloys.

-Cobalt is a powerful and stable colorant used in glass, glaze, enamel, and even paint. As little as 2 PPM can produce a recognizable tint, thus cobalt is often cut in a medium to make it easier to weigh and distribute in a mix.

-It is not volatile even at 1400C.

-Various raw forms are available and all break down to cobaltous oxide (CoO), which is the stable form that combines with the glass melt to produce color. These include black stable cobalto-cobaltic oxide (cobaltosic oxide) Co3O4, which has a 93% conversion ratio and decomposes to liberate oxygen at 800C. Grey cobaltic oxide (Co2O3) is 90% CoO and mauve cobalt carbonate (CoCO3) has 63% effective stain content. Cobalt dioxide (CoO2) is not marketed for ceramics.

-Because cobalt is quite soluble in glaze melts, it has little or no opacifying effect.

-Although cobalt has a high melting point, it is a powerful glaze flux, dissolving readily in most glazes, especially alkaline and boron types. This active nature causes it to diffuse, making it difficult to maintain a clean edge on painted decoration, especially overglaze.

-It is very dependable under both oxidizing and reducing furnace conditions, fast and slow firing.

-Cobalt is used in a wide array of decal inks, underglaze colors, body stains, and colored glazes.

Properties

Glaze Color Cobalt is often calcined with alumina and lime for soft underglaze colors. Stains often employ mixes of alumina, cobalt, and zinc for softer blue colors.
Glaze Color Cobalt is used in combination with manganese and selenium to mask excess yellow coloration (yellow plus blue gives green which is masked by the pink of selenium).
Glaze Color Combinations with iron and manganese can give a slate blue.
Glaze Color With barium shades of blue-green are possible.
With magnesia the color range is from violet to lilac.
Glaze Color With chrome and manganese blue-black and black are common.
Glaze Color Cobalt is a classic and reliable blue colorant at all temperatures and in most types of glazes. The shade of blue can, however, be affected in many ways by the presence of different oxides. Cobalt is powerful and often less than 1% will give strong color. If the color needs to be toned down, additions of iron, titanium, rutile, and nickel may work.

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Properties
Glaze Color	Cobalt is often calcined with alumina and lime for soft underglaze colors. Stains often employ mixes of alumina, cobalt, and zinc for softer blue colors.
Glaze Color	Cobalt is used in combination with manganese and selenium to mask excess yellow coloration (yellow plus blue gives green which is masked by the pink of selenium).
Glaze Color	Combinations with iron and manganese can give a slate blue.
Glaze Color	With barium shades of blue-green are possible. With magnesia the color range is from violet to lilac.
Glaze Color	With chrome and manganese blue-black and black are common.
Glaze Color	Cobalt is a classic and reliable blue colorant at all temperatures and in most types of glazes. The shade of blue can, however, be affected in many ways by the presence of different oxides. Cobalt is powerful and often less than 1% will give strong color. If the color needs to be toned down, additions of iron, titanium, rutile, and nickel may work.