- Cobalt Carbonate is an inorganic compound used in ceramics as a blue colorant. Its chemical formula is CoCO3, and it is available in powdered form. Though it is lavender in color in its dry form, cobalt carbonate produces vibrant shades of blue under the proper conditions. In terms of colorant strength, cobalt carbonate is a weaker form of cobalt oxide (Co3O4), though both are good sources of cobalt.
- The potential uses of cobalt in ceramics are many. It can be used alone - applied to the surface of an unfired pot and then fired to the temperature of the clay body. Mixed with other colorants, such as magnesium, and added to a glaze, cobalt can produce more purple/reddish blues in oxidation/reduction firings. With this colorant, you can produce blue slips, if mixed with white clay bodies. In this way you can achieve various shades of blue of different intensities. Additionally, if mixed in the proper proportions with iron and manganese, intense blacks can be achieved. In general, cobalt is a relatively stable colorant in all kiln atmospheres.
- Cobalt carbonate is also a common component in ceramic decals, and it is the colorant that has long been associated with the pottery of the Delft period. Using cobalt in washes and with brush application provides yet another method of vibrant surface decoration on pottery.
- Recommended concentrations of cobalt are as follows:
- 0.25- 2% in slips
- 0.25 - 1% in glazes
- In its powdered form, cobalt carbonate can cause skin, eye and/or respiratory system irritation. Please use proper precautions, including protective coverings, when working with this substance.