Manganese Dioxide MnO, MnO2, and MnCO3
- Refractory at temps below 1976°F
- Acts as flux at higher temps
- Melts at 3002°F
- Produces browns, yellows, purples, and metallic glazes
- Also used in black stains and glazes and as clay body stain in black clays
- Small amounts of manganese are easily dissolved in glaze but larger amounts will form crystallized surfaces
- Manganese carbonate releases gases at 1976°F to become MnO
- May cause bubbling in glaze
- Toxic and volatilizes at higher temps
- Should be used with extreme caution
- Manganese carbonate is also dust hazard
- Is insoluble in pure water but soluble in hydrochloric acid.
- Sources are manganese dioxide, manganese carbonate and Barnard Clay.