from
The Collaborative International Dictionary of English v.0.48
Zaffer \Zaf"fer\, n. [F. zafre, safre; cf. Sp. zafra, safra, It.
saffera, G. zaffer; all probably of Arabic origin. Cf.
{Zaphara}.]
A pigment obtained, usually by roasting cobalt glance with
sand or quartz, as a dark earthy powder. It consists of crude
cobalt oxide, or of an impure cobalt arseniate. It is used in
porcelain painting, and in enameling pottery, to produce a
blue color, and is often confounded with smalt, from which,
however, it is distinct, as it contains no potash. The name
is often loosely applied to mixtures of zaffer proper with
silica, or oxides of iron, manganese, etc. [Written also
{zaffre}, and formerly {zaffree}, {zaffar}, {zaffir}.]
[1913 Webster]