Craig Martell on mon 14 oct 96
According to Frank Hamer in The Potter's Dictionary of Materials and
Techniques,
cobalt oxide is non toxic. So a cobalt ox. wash on tableware may not make
anyone
ill, but why push it. Perhaps this type of surface treatment is better
suited to non-
utilitarian pieces. Most ceramic colorants need a certain amount of silica
to keep
them stable. After years of use you may find that the pleasant black color
made by
cobalt ox. is no longer as nice as it had been.
Craig Martell-Oregon USA
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