Egyptian Blue

: ON THE PRIMARY, BLUE.

called by Vitruvius, Coeruleum, is frequently found on the walls of

the temples in Egypt, as well as on the cases enclosing mummies. Count

Chaptal, who analysed some of it discovered in 1809 in a shop at

Pompeii, found that it was blue ashes, not prepared in the moist manner,

but by calcination. He considers it a kind of frit, of a semi-vitreous

nature; and this would appear to be the case from Sir H. Davy obtaining

a imilar colour by exposing to a strong heat, for two hours, a mixture

of fifteen parts of carbonate of soda, twenty of powdered flints, and

three of copper. The colour is very brilliant when first made, and

retains its hue well in distemper and decorative painting; but it has

the common defect of copper blues of turning green in oil, when ground

impalpably for artistic use. One remarkable effect of this copper

smalt--for it is nothing else--is, that by lamp-light it shows somewhat

greenish, but shines by day with all the brightness of azure. Merimee

believes that Paul Veronese employed this sort of blue in many of his

pictures where the skies have become green.