Coeruleum Of Pliny Were A Blue Copper Earth However That May Be In

these days both names signify cobalt compounds, coeruleum being a

stannate of cobalt, and cyanine a mixture of cobalt and Prussian blue.

Unlike the former, cyanine, being composed of two old colours, can lay

no claim to originality. In the fourth chapter it was observed, "it is

quite possible for the artist to multiply his pigments unnecessarily.

Colours are sometimes brought out under new names which have no claim to

be regarded as new colours, being, indeed, mere mixtures. Compound

pigments like these may most frequently be dispensed with, in favour of

hues and tints composed extemporaneously of original colours upon the

palette." Whether these remarks are applicable to cyanine or not is a

question for artists to decide: in our opinion, with so many semi-stable

original pigments, the introduction of semi-stable compounds is to be

deprecated. Cyanine is a rich, deep, transparent blue, but its richness

and depth, as well as to a great extent its transparency, depend upon

Prussian blue, which is not strictly stable. Hence the peculiar

properties of cyanine remain unchanged only so long as the Prussian blue

itself, the pigment losing its colour by degrees on exposure to air and

light, and gradually assuming the tint of the paler but more permanent

cobalt. A mixture, be it remembered, necessarily partakes of the

qualities of its constituents, and if one of these be fugitive, the

compound cannot preserve its original hue.

Within the last few years, a compound similar to cyanine has appeared,

Citrine; While Mixed With Purple It Becomes The Other Extreme Colour facebooktwittergoogle_plusredditpinterestlinkedinmail