Cobalt Oxide CoO, Co2O3, Co3O4, and CoCO3
- Strongest of all colorants available to potters
- less than .25% will produce blue color
- Powerful flux that melts at 3281°F
- In spite of its high melting point, it’s soluble in glazes and will disperse very well
- Is unaffected by oxidation and reduction, and is used as colorant in black stains and glazes
- Cobalt Oxide (Co3O4 reduces to CoO at 1472°F releasing an oxygen atom, which can cause splattering of glaze if firing is too fast
- Approximately 1.4 times as strong as cobalt carbonate
- Tot always precisely true because when you buy cobalt oxide, you get a mixture of forms of cobalt whose purity varies, but all decompose at high temps to form CoO.
- Like sodium and potassium oxides, it’s a very active flux
- dissolving readily in glaze to give even coloration
- If sourced from cobalt oxide sometimes causes speckling
- From cobalt carbonate produces very even blue color
- Not easy to obtain hard-edged line with any form of cobalt because it will diffuse or bleed into surrounding glaze
- Ceramic dealers supply
- Cobalt carbonate (usually pink)
- Cobalt oxide (usually black powder)
- Cobalt sulfate (also pink and water soluble)
- Cobalt is a by-product of winning nickel and copper
- Ore of these metals may contain cobalt concentrate. Then sold to manufacturers who convert it to cobalt oxide, carbonate, and sulfate
- VERY TOXIC (like nickel)
- HANDLE with CARE