Gartside, Mary
An Essay on Light and Shade, on Colours, and on Composition in General — London, 1805

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Since the foregoing sheets were printed, it has occurred to me, that
something more was wanting to render them as useful as I could wish; in
short, that, though the theory should he clear, difficulties might arise in
practice, to those who are unused to mixing and preparing their own colours;—
such is the case with most Ladies, from the trouble with which it is attended;
•^-and that an arrangement of the different pigments into classes, correspond-
ing with the annexed tables, according to their respective degrees of brilliancy,
may be necessary, making the Prismatic Spectrum the standard. In order to
do this, it will be requisite, as it were, to analyse each colour, and ascertain
which are pure and which are compounds; also to find out what proportion
of each tint there is in the latter. But this will be attended with difficulty :
for we cannot proceed in a chemical way, and separate the particles of each
colour. The only mode seems to be, to form, by a mixture of the prismatic
tints, an imitation of the different pigments now in use, observing the pro-
portions and quality of each combined colour, and thence draw a conclusion
as to the strength and brilliancy of the imitating colour. On trial, it appears
that we have very few colours which will in themselves express those in the
Prismatic Spectrum; but that there requires a combination of different ones,
to produce any thing like an imitation of them: and as the greater part of
our colours are compounds, it proves in how very few cases we can have any
great brilliancy of colouring*; for it has already been shewn that no com-
pound colour can come so forward to the eye, as those purely prismatic.

The compound colours in the spectrum are composed of only ttoo com-
bined colours, therefore any pigment that can be imitated, two of the three
primitives, the yellow, red, and blue, will class with them, and belong to the
first table of colours ; but when three or four are combined, a degree of
obscurity takes place, which ranks them in a lower order. 1 must here ob-

* Which shews how much room there is for. improvement in the art of colour-making.

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