Called When Levigated Body White Is An English White Lead In The

: ON COLOURS AND PIGMENTS INDIVIDUALLY.

form of scales or plates, sometimes grey on the surface. It takes its

name from its figure, is occasionally equal to Crems white in colour,

and generally surpasses in body all other white leads. In composition,

it is a mixture of protocarbonate and hydrated oxide of lead, the latter

decreasing the opacity of the product according to the greater

proportion in which it is present.



TTITLE FLEMISH WHITE, OR S LPHATE OF LEAD



Is an exceedingly white precipitate from any solution of lead by

sulphuric acid, much resembling the blanc d'argent. It is inferior,

however, both in body and permanence to the ordinary carbonate. Hence,

white lead which has more or less been converted by sulphuretted

hydrogen into sulphide, and again been converted into sulphate by

oxidation, with a view to restoring its colour, becomes peculiarly

liable to the influence of impure air.



TTITLE LONDON AND NOTTINGHAM WHITES.



The best of these do not essentially differ from each other, nor from

the white leads of other manufactories. The latter variety, being

prepared from flake white, is usually the greyer of the two.



TTITLE PATTISON'S WHITE, OR OXYCHLORIDE OF LEAD



Is a mixture of chloride and oxide of lead, formed by precipitating a

solution of chloride of lead with soda, potash, lime, or baryta, in the

caustic or hydrated state. It would appear that when the oxychloride is

used as a paint, the oxide contained in it gives rise to an oleate of

lead, and, in consequence of this saponaceous matter, is capable of

spreading over an extended surface. The product has been described as

possessing properties which are superior to those of white lead,

inasmuch as it does not so readily blacken as the latter body. Dr. Ure,

however, found that water removes the chloride of lead from the paint

compounded of this article, and, consequently, that it is not so

effectual as the carbonate. As an artist's pigment, a partially soluble

compound of lead can decidedly not be eligible.



TTITLE ROMAN WHITE



Is of the purest white colour, and differs only from blanc d'argent in

the warm flesh tint of the external surface of the large square masses

in which it is commonly prepared.



Besides the foregoing, there are other white leads, generally foreign,

cheaper, and adulterated. Many of these are mixed with a small quantity

of charcoal, indigo, or Prussian blue, so that the dead yellowish shade

which they present may be enlivened to a brighter hue. Among them may be

named--



TTITLE CERUSE.



A French variety, not necessarily, but not unfrequently, mixed with

different chalky earths in various proportions; and the following

Belgian kinds:



TTITLE DUTCH WHITE,



Containing three fourths of sulphate of baryta.



TTITLE HAMBURGH WHITE.



A mixture of two parts of heavy spar and one of the plumbous compound.



TTITLE KREMSER WHITE,



Differing from the rest in being unadulterated.



TTITLE VENETIAN WHITE



Composed of heavy spar and the carbonate in equal proportions.





ZINC WHITES.



TTITLE CHINESE WHITE.



The introduction, in 1834, of this peculiar preparation of oxide of zinc

has proved an incalculable boon to water-colour painters, who formerly

had no white which combined perfect permanency with good body in

working. Its invention obviated the necessity for using white lead, a

pigment which, though it may be employed with comparative safety in oil,

is quite unfitted for water. Since the period of its production, Chinese

white has been generally preferred by water-colour artists, as being the

most eligible in their peculiar department. Previous to that period, the

complaints of whites changing were of constant occurrence; but in no

instance has any picture, in which this white has been used, suffered

from its employment. To the colour of oxide of zinc, sulphuretted

hydrogen is altogether harmless; sulphide of zinc being itself white.

The variety under notice works and washes well, possesses no pasty or

clogging properties, and is prepared beautifully white. Moreover, it has

the desirable quality of dense body; so much so, that, as the painter

works, his effects remain unaltered by the drying of the colour. It may

likewise be safely mixed with all other pigments, the following blending

very satisfactorily with the white for opaque lights--cadmium yellow,

orange, and red; gamboge; aureolin; yellow ochre; vermilion; and light

red. Without the artistic drawbacks of constant white or the chemical

defects of white lead, and retaining the advantages of both, Chinese

white cannot but be considered as a most important addition. It is a

matter of regret that this pigment is not equally efficacious in oil.



TTITLE ZINC WHITE



Is either the anhydrous oxide, the hydrate oxide, or hydrated basic

carbonate of zinc. It varies in opacity and colour according to the mode

of manufacture, and the purity of the compound, but may always be relied

upon as permanent. The whiteness of the best samples rivals that of

white lead, and it is not tarnished like the latter by sulphurous

vapours. In opacity it never equals white lead, and might perhaps serve

advantageously as a glaze over that pigment, either alone or compounded

with other colours; as well as act as a medium of interposition between

white lead and those colours which are injured by it, such as gamboge,

crimson lake, &c. When duly and skilfully prepared the colour and body

of this pigment are sufficient to qualify it for a general use upon the

palette in oil: in water it has been superseded by Chinese white.



Occasionally, starch, chalk, white clay, and carbonate of baryta, are

employed as adulterants; none of which, however, are inimical to

stability.



As a pigment, zinc white may be said to be innoxious. As oxide of zinc

does not readily form a saponaceous compound with fats or oil like white

lead, the paint prepared with it and ordinary linseed oil does not dry

or harden so rapidly. For the purpose of causing it to be more

siccative, the oil was boiled with a large quantity of litharge, but by

this method the white was liable to tarnish on meeting with foul air.

Instead of litharge, experiments have led to the choice of salts of

zinc, such as the chloride or sulphate, a small percentage of which, on

being mixed with the oil or oxide, confers upon it the property of

rapidly hardening. The same result is attained by employing an oil,

dried by boiling with about five per cent of peroxide of manganese. In

either case, a paint retaining its white colour permanently is produced.

These agents might, with advantage, be more generally used in the place

of litharge for rendering oils siccative. Many pigments which are not

naturally affected by sulphurous emanations are apt to suffer if mixed

with an oil made drying by means of lead.



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