Mountains Of Kernhausen Whence It Is Sometimes Called Hungary Green





It is prepared from malachite, a beautiful copper ore employed by

jewellers, and is a hydrated dicarbonate of copper, combined with a

white earth, and often striated with veins of mountain blue, to which it

bears the same relation that green verditer bears to blue verditer. The

colour, which may be extracted from the stone by the process followed

for native ultramarine, varies from emerald-green to grass-green, and

inclines to grey. It has been held in great esteem by some, and

considered strictly stable, on the assumption, probably, that a pigment

obtained from a stone like ultramarine, and by the same method, could

not be otherwise than permanent. That it is so, with respect to light

and air, there is no denying; but the green, when separated from the ore

and purified for artistic use, is merely a carbonate of copper, and

therefore subject to the influence of damp and impure air, in common

with other non-arsenical copper colours. As a pigment, native malachite

green has the same composition, or very nearly the same, as that which

can be artificially produced, and answers to the same tests. Water-rubs

of the two varieties which we exposed to an atmosphere of sulphuretted

hydrogen became equally blackened by the gas. Practically, there is

little or no difference between them: both preserve their colour if kept

from damp and foul air, both are injured by those agents, and both are

liable to darken in time, especially when secluded from light. The

artificial, however, can be obtained of a much finer colour than the

natural, which it may be made to resemble by admixture with mineral

gray. On the whole, they can scarcely be recommended for the palette,

and are certainly inferior in durability to Scheele's and Schweinfurt

greens. In fresco painting they have been pronounced admissible; but,

apart from the question of damp, we should deem the conjunction of lime

with carbonate of copper not favourable to permanence. By the action of

alkalies, even the native green malachite may be converted into blue;

and it becomes a question whether the dingy greenish-blue on some

ancient monuments was not originally malachite green.



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More Directly Of The Secondaries Purple And Green In Each Of Which Mummy Brown Or Egyptian Brown Is A Bituminous Product Mixed With facebooktwittergoogle_plusredditpinterestlinkedinmail

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