Ochre Oxford Ochre Stone Ochre Di Palito &c Are Native





earths, consisting chiefly of silica and alumina in combination with

iron, which latter forms the principal colouring matter. They are among

the most ancient of pigments, and their permanency is proved by the

state of the old pictures. In a box of colours found at Pompeii, and

analyzed by Count Chaptal, he discovered yellow ochre purified by

washing, which had preserved its original freshness. They may all be

produced artificially in endless variety as they exist in nature, and

are all converted by burning into reds or reddish-browns. Several ochres

are found in the natural state of so very fine a quality, that they

require no other preparation than that of being washed. Their colours

may be imitated to a certain extent by means of iron alone, uncombined

with silica and alumina; but such ferruginous preparations are not

equally durable, and as their chemical action is stronger, they are more

likely to affect those pigments which are damaged by iron. It often

happens in colours that one component of weak stability, or powerful

for evil, is strengthened and held in check by another; thus in the case

of the ochres, the silica and alumina by keeping a tight hand on the

iron, both ensure its safety, and prevent it injuring others.



TTITLE YELLOW OCHRE,





Numerous Colours Are Likewise Injured By Lime And Fire And Cannot Of Late Years In The German Coelin Known Here As Cerulian Blue And facebooktwittergoogle_plusredditpinterestlinkedinmail

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