Grey is the second and intermediate of the neutral colours, standing between white and black. True or normal grey is only obtainable by admixture of pure white with pure black, various proportions of which afford numerous tones of pure grey. In practice it may likewise be produced by a thin wash of black over white. The neutral grey differs from the semi-neutral gray in not being coloured by any primary, secondary, tertiary, or semi-neutral; hence any blue, purple, olive, or gray added to it, at once destroys the neutrality of grey, and converts it into gray. Thus easily defiled and changed in class, grey is rather a theoretical than a practical colour. To our knowledge, there has never been a true grey pigment, that is, one composed exclusively of pure white and pure black; the grays known to the palette as Mineral Grey and Payne's Grey having been incorrectly named. Practically, the nearest approach to a normal grey is furnished by Black Lead, which forms grey tints of greater permanence and purity than the blacks in general use, and is now employed for this purpose with approved satisfaction by experienced artists.

Being compounded of white and black, grey partakes in some measure of the qualities of both those colours—for colours, as a matter of convenience, they must be called; although white is often spoken of as no colour, and black as the complete extinction of all colour. With white predominant, grey is used, pure or coloured, for the general lights of a picture; just as, with black predominant, grey is employed, pure or coloured, for the shades. It helps to subdue the absolute white, and to make the absolute black conspicuous. Black and white are in some respects complementary to each other, and when in contact, appear to differ more from each other than when viewed separately: both show with best effect when harmonised by a medium of grey, normal or otherwise. The primary colours, also, gain in brilliancy and purity by the proximity of grey. With dark colours, such as blue and violet, and deep tones in general, grey forms assortments of analogous harmonies; while with the luminous colours, such as red, orange, yellow, and the light tints of green, it forms harmonies of contrast. Although grey never produces a bad effect in its assortments with two luminous colours, in most cases the association is dull and inferior to black and white. The only instance in which grey associates with two such colours more happily than white is that with red and orange. Grey is inferior to both white and black with red and green, red and yellow, orange and yellow, orange and green, yellow and green; and is not so good as white with yellow and blue. In association with sombre colours, such as blue and violet, and with broken tones of luminous colours, grey gives rise to harmonies of analogy which have not the vigour of those with white; but if the colours do not combine well together, it has the advantage of separating them from each other. Associated with two colours, one sombre, the other luminous, grey will perhaps be better than white, if white produces too strong a contrast of tone: on the other hand, grey will be preferable to black, if that has the inconvenience of increasing too much the proportion of sombre colours. Grey associates more happily than black with orange and violet, green and blue, or green and violet.

288. MIXED GREY.

When a ray of solar light (a sunbeam) is passed through a prism of flint glass, and the image or 'prismatic spectrum' received upon a screen of white paper, it is found to consist of numerous rays of different colours, which are conveniently divided into six groups—red, orange, yellow, green, blue, violet. Optically, the union of red, yellow, and blue, in proper proportions, constitutes white light; whether the rays of the three separate colours are mixed, or of one with the other two in combination: the same result ensues when red is mixed with green as if it were mixed with blue and yellow, because green is composed of blue and yellow. Consequently, any primary mixed with a secondary composed of the other two primaries, forms the complement of rays necessary to constitute or make up white light, and vice versÂ.

There is, however, a very great difference between the results arising from the mixture of the pure coloured rays of the spectrum, and those from material colours or pigments. When, by means of a convex lens, we reunite the coloured rays of the spectrum white light is reproduced; but when we mix coloured materials, blues, yellows, and reds, the compound is never white, but grey or black; even if these coloured pigments are taken in the exact proportions in which their colours exist in the spectrum. Ultramarine, our purest blue, reflects red rays as well as blue rays; aureolin, our purest yellow, reflects blue as well as yellow rays; and carmine reflects yellow as well as red rays. Now whenever the third primary colour is present in any mixture of coloured materials, it tends to form grey, by mixing with a sufficient quantity of the other coloured rays to neutralize it, and the presence of this grey breaks or tarnishes the pure colour. Hence it is that to obtain a pure green, a blue should be taken tinged with yellow rather than with red, and a yellow tinged with blue: if there were chosen either a blue or a yellow tinged with red, this latter colour would go to form some grey in the compound, which would tarnish the green. In like manner, to produce pure orange, neither the red nor the yellow must contain blue; and similarly with pure purple, neither the blue nor red should contain yellow.

As regards pigments, then, a proper mixture of yellow, red, and blue; or of yellow and purple, red and green, or blue and orange; or of orange, green, and purple, affords black if sufficiently intense, and grey if sufficiently diluted. The black may be rendered grey by spreading a thin wash over a white ground, or by the direct addition of white. It must be remembered, however, that suitable proportions of the component colours are essential. When all three of the primaries, for example, are mixed together, colour is neutralised according as they are compounded of equal strength and in right quantities: if proper proportions are observed, pure black or normal grey results; but if not, there will be produced a coloured black or a coloured grey, an excess of one or two of the primaries giving rise to brown, marrone, or gray.

A reference to the lists of permanent primary and secondary pigments will show to what extent durable greys can be compounded. As these pigments differ so widely in hue and other properties, no fixed rules can be given for their admixture: to ensure neutrality, practice and a correct eye are indispensable. Without perfect neutrality, difficult to attain and rarely to be met with, grey ceases to exist. In pure white, pure grey, and pure black, colour is, so to speak, conspicuous by its absence.