Cobalt as a dark blue colourant for glass has been known since the Bronze Age in Europe. Not being a specialist I cannot say what was used as the source of the cobalt but can ask.
Yours,
Peter Northover
--
Dr Peter Northover, Materials Science based Archaeology Group,
Department of Materials, University of Oxford
Tel +44 (0)1865 283721; Fax +44 (0)1865 841943 Mobile +44 (0)7785 501745
e-mail [log in to unmask]
|