RED O K E R,
Is a native earth, brought chiefly from O.xford-
fhire, and burnt afterwards (by thofe who pre-
pare it) in large ovens, till by calcination it becomes
red. It is very ufeful as well in the more'delicate
as coarfer paintings in oil, for it (lands infalliby.
For nicer purpofes it fhould be wafhed over ; but for
others it may be ufed in the ftate in which it is found
in the fhops.
Class II. * Of BLUE COLOUR S.
Ultramarine isabricht blue colour, of tbehjsh-
■ O J * O
eft value in every kind of painting; being equally
ferviceable in all, even in enamel. It has a tranf-
parent effect in oil, and in lome degree in water,
and will ftand without the leaft hazard of flying. By
reafon of its high price, Pruifian blue, lias been
much introduced, to the prejudice of painting in ge-
neral; as the fk:es or landfkapes and many other
parts of modern pictures, fliew the lofs of ultra-
marine, bv their changing irom a warm or clear
blue, to a faint green or olive -teint. The methods
have been continually varied by thofe who have at-
* Class II. B L U E.
Ultramarine afh.es. Smalt.
Piuliian blue. Bice.
Verditer. Litmus, or latmus,
Cehdrc blue, or Sanders bine.