Lake &c And Are Obtained From The Coccus Cacti An Insect Found On





a species of cactus, from the juice of which it extracts its

nourishment. This coccus is a native of Mexico, where two kinds are

recognised, under names which signify wild cochineal and fine cochineal.

The latter may be considered a cultivated product, its food and wants

being carefully attended to, while the former is left in a natural

state, and is less valuable. Wild cochineal is distinguished by having a

woolly downy coat, which is not the case with the fine cochineal. The

females, of which there are from one hundred and fifty to two hundred

for each male, are marked by the absence of wings, and constitute the

commercial article. They are generally killed by immersion in boiling

water, which causes them to swell to twice their natural size, and are

then dried and packed for market. The insects shrivel in drying, and

assume the form of irregular grains, fluted and concave. The best sorts

have a silvery-grey colour, with a purplish reflection, and seem to be

dusted with a white powder. This appearance is often given by means of

heavy spar, carbonate of lead, Venice talc, &c. A good lens, however,

will mostly expose the fraud; or it may be detected by macerating the

insect in water, and allowing the loosened pulverised particles to

settle.



Cochineal is a very rich colouring substance, yielding about half its

weight of real colouring matter, which may be easily extracted by

boiling in water. Dr. Warren De La Rue, who examined the living animal,

states that on piercing the side of the insect a purplish-red fluid

exuded, containing the colouring matter in minute granules. This

colouring matter he succeeded in obtaining pure, in the form of a

purple-brown friable mass, pulverizable to a fine red powder,

transparent when viewed by the microscope, and soluble both in water and

alcohol in all proportions. At temperatures above 136 deg. it decomposed,

and by alkalies its colour was turned to purple. These facts account for

the care required in drying cochineal lakes, and for their liability to

change of hue when in contact with alkaline substances, as in mural

decoration.



The lakes of cochineal may be known from those of the dye-woods by their

solubility in ammonia, a liquid which purples but does not dissolve the

colours produced from the latter.



TTITLE CARMINE.



A name once given only to the fine feculences of kermes and cochineal

tinctures, now denotes generally any pigment which resembles them in

beauty, richness of hue, and powdery texture. We have, therefore, blue

and other coloured carmines, though the term is usually confined to the

crimson and scarlet lakes of cochineal. As at present commonly

understood, carmine is that preparation of cochineal which contains the

most colouring matter and the least aluminous base. Hence it is the

richest, deepest, most intense, and most permanent. Although not to be

classed as durable, yet by reason of its extreme depth, carmine is more

stable than the weaker crimson, scarlet, and purple lakes. When

well-made, pure, and employed alone and in body, it has been known to

retain its colour for years, especially if protected by oil or varnish.

In tint with white lead, however, it has no stability; and though little

affected by impure air, in glazing it is soon discoloured and destroyed

by the action of light. Of great power in its full touches, it possesses

considerable clearness in the pale washes, and works admirably. In

landscape, carmine is seldom used, the colour being chiefly valued in

flower painting and illumination.



It has been erroneously stated that the finest carmines cannot be made

in England, owing to a want of clearness in the atmosphere and a

scarcity of sunshine. For many years, however, they have been produced

in this country, not only finer than any foreign preparations, but

equally good in winter as in summer.



Carmine is sometimes sophisticated with starch, vermilion, and with

alumina not formed in the process of manufacture. Occasionally also, a

portion of the animal matter of the cochineal from which it has been

obtained is left mixed with it. These accidental or intentional

impurities may mostly be detected by heating the carmine with liquid

ammonia, which entirely dissolves the colouring matter and leaves the

impurities in an insoluble state.



TTITLE CRIMSON LAKE



Is a cochineal pigment containing more aluminous base than carmine, and

is consequently weaker in colour and less stable. Deficient in much of

the depth and brilliancy which belong to the latter, it is more commonly

employed and more generally useful. This lake is of service in mixing

tints, to impart richness, in flower painting and illumination, and is,

like all cochineal colours, of greater utility in water than in oil.

With cobalt and gamboge it yields an excellent gray, and with cobalt

alone a fine purple for heather. Distant hills may be strengthened with

a tint of French blue and lake, and Vandyke brown with the crimson will

be found admirable for a rich coloured foreground. Many other beautiful

tints, unexceptionable in an artistic sense, are afforded by crimson

lake on admixture. It should be remembered, however, that not one of

them is permanent as far as the lake is concerned. All cochineal

pigments are more or less affected by strong light, which weakens their

tints, and in time deprives them of colour; and it is not by being

compounded that a fugitive colour is rendered durable.



TTITLE SCARLET LAKE



Is prepared in the form of drops from cochineal, and is of a fine

transparent red colour and excellent body, though, like other lakes, it

dries slowly. Discoloured and destroyed by strong light both in water

and oil, and not permanent in tint with white lead or in combination

with other pigments, it possesses the common attributes of cochineal

lakes. Yet when well prepared, used in sufficient body, and not unduly

exposed, it has been found to last a lengthened period; but it ought

never to be employed in glazing, nor at all in works that aim at high

reputation and stability. It is in general tinted with vermilion, which

has probably been mixed with lakes at all times to give their scarlet

hue and add to their weight; for upon examining with a powerful lens

some fine pictures of ancient masters, in which lake had been used in

glazing, particles of vermilion were apparent, from which lake had

evidently flown. Unfortunately, these lakes are injured by vermilion as

they are by lead, so that glazings of cochineal over vermilion or lead

are particularly apt to vanish. This effect is very remarkable in

several pictures of Cuyp, where he has introduced a figure in red from

which the shadows have disappeared, owing to their having been formed

with lake over vermilion. The scarlet hue of this lake should properly

be imparted to it during the process of manufacture, and not by

subsequent mechanical admixture.



TTITLE PURPLE LAKE



Is a species of crimson lake with a purple cast, transparent and

deep-toned, and useful in shadows: in other respects resembling that

pigment. Red being its predominant colour, we have preferred classing

this so-called purple among the reds, in spite of its name. On the whole

it is more durable than crimson lake.



TTITLE FLORENTINE LAKE



Differs from scarlet lake only in the mode of preparation. Formerly the

lake so called was extracted from the shreds of scarlet cloth. The same





Krems In Austria It Is Also Called Vienna White Being Brought From Lake A Term Derived From The Lac Or Lacca Of India Is The Name Of facebooktwittergoogle_plusredditpinterestlinkedinmail

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