Fields Chromatography | Page 9

of pigments
individually; not for the purpose of destroying the artist's confidence,
but as a caution, and a guide to the availing himself of their powers
properly.
It is, therefore, the lasting under the usual conditions of painting, and
the common circumstances to which works of art are exposed, that

entitles a colour to the character of permanency; and it is the
not-so-enduring which attaches to it rightly the opposite character of
evanescence: while a pigment may obtain a false repute for either, by
accidental preservation or destruction under unusually favourable or
fatal circumstances.
Many have imagined that colours vitrified by intense heat are
consequently durable when levigated for painting in oil or water. Had
this been the case, the artist need not have looked farther for the
furnishing of his palette than to a supply of well-burnt and levigated
enamel pigments. But though such colours for the most part stand well
when fluxed on glass, or in the glazing of enamel, they are nearly,
without exception, subject to the most serious changes when ground to
the degree of fineness necessary to their application as pigments, and
become liable to all the chemical changes and affinities of the
substances which compose them. These remarks even apply in a
measure to native products, such as coloured earths and metallic ores.
Others have not unreasonably supposed that when pigments are locked
up in varnishes and oils, they are safe from all possibility of change.
The assumption would be more warranted if we had an impenetrable
varnish--and even that would not resist the action of light, however
well it might exclude the influence of air and moisture. But, in fact,
varnishes and oils themselves yield to changes of temperature, to the
action of a humid atmosphere, and to other influences: their protection
of colour from change is therefore far from perfect.
Want of attention to the unceasing mutability of all chemical
substances, as well as to their reciprocal actions, has occasioned those
changes of colour to be ascribed to fugitiveness of the pigment, which
belong to the affinities of other substances with which it has been
improperly mixed and applied. It is thus that the best pigments have
suffered in reputation under the injudicious processes of the painter;
although, owing to a desultory practice, the effects and results have not
been uniform. If a colour be not extremely permanent, dilution will
render it in some measure more weak and fugitive; and this occurs in
several ways--by a too free use of the vehicle; by complex mixture in

the formation of tints; by distribution, in glazing or lackering, of
colours upon the lights downward, or scumbling colours upon the
shades upward; or by a mixed mode very common among the Venetian
painters, in which opaque pigments are combined, as umber and lake.
The fugitive colours do less injury in the shadows than in the lights of a
picture, because they are employed pure, and in greater body in
shadows, and are therefore less liable to decay by the action of light,
and by mixture. Through partially fading, moreover, they balance any
tendency to darken, to which the dead colouring of earthy and metallic
pigments is disposed.
The foregoing circumstances, added to the variableness of pigments by
nature, preparation, and sophistication, have often rendered their effects
equivocal, and their powers questionable. These considerations enforce
the expediency of using colours as pure and free from unnecessary
mixture as possible; for simplicity of composition and management is
equally a maxim of good mechanism, good chemistry, and good
colouring. Accordingly, in respect to the latter, Sir Joshua Reynolds
remarks, "Two colours mixed together will not preserve the brightness
of either of them single, nor will three be as bright as two: of this
observation, simple as it is, an artist who wishes to colour bright will
know the value."
There prevail, notwithstanding, two principles of practice on the palette,
opposed to each other--the one, simple; the other, multiple. The first is
that of having as few pigments as possible; and consists, when carried
to the extreme, in employing the three primary colours only. The
second is that of having a number of pigments; and consists, also when
carried to the extreme, of employing as many, if possible, as there are
hues and shades of colour.
On the former plan, every tint requires to be compounded; on the latter,
one pigment supplies the place of two or more. Now, the more
pigments are mixed, the more they are deteriorated in colour,
attenuated, and chemically set at variance. Original pigments, that is,
such as are not made up of two or more colours, are purer in hue and
generally more durable than those compounded. Hence pure

intermediate tints in single, permanent, original pigments, are to be
preferred to pigments compounded, often to the