Coloured decoration on gold grounds ought to be outlined in black, or some very dark colour, in order to prevent the gold from overpowering the colour and making it look ineffective. When highly relieved enrichments are gilt, the ground behind them may be “picked out” in strong colour, such as vermilion, deep cobalt blue, or black in cases where an effect of penetration is desired, but in proportion to the lowness of the relief the background colouring may be lessened in strength or intensity. It must be pointed out, however, that ornament in very low relief, if gilded, will require a more strongly coloured background than in the case of ornament that may be simply coloured, but not gilt.
The small interval, or concord of closely related tones.—It might be suggested that the natural development, or sequence of purely monochromatic colouring to a full and rich polychromy would be of that kind of colour harmony which is known as the small interval, which, in decoration, is expressed by the concord of closely related colour tones. It may be also defined as a harmony of colour analogy, a kind of gradation where colours and their tints are separated by a little distance or interval from each other in the chromatic circle. The colouring of natural objects and phenomena afford endless examples of the small interval. The plumage of birds, wings of insects, foliage of trees and plants, flowers, shells, some minerals, and the sunset sky may be mentioned as some of the illustrations of this kind of harmonious colour gradation, where the various tints and shades of closely related colours are cunningly arranged by nature in delicate, yet decided contrasts, not of hue, but of analogous tones. For example, a green-blue may pass into a violet-blue, by a gradual series of separated tints, but the latter colour must be kept at the shade of violet just before it is overcome by red, and the former must not be overpowered by yellow. The colour of a peacock’s neck-plumage affords a good illustration of this kind of green-blue to violet-blue colouring by gradation of shades. A similar gradation is where an orange-red passes gradually into a crimson-red, but neither yellow in the first-named colour nor blue in the crimson must be permitted to overcome them. The decorator being concerned with the use of broken colours—that is, pure colours modified by mixture of black, white or grey—for the covering of large spaces such as walls, ceilings and woodwork panels, can therefore adopt the principle of the small interval in architectural colouring with advantage and success, by using any group of closely related colours for his scheme; and further, if he desires to intensify or enliven the latter, he can do so by the use of small quantities of other contrasting colours introduced in the cornice, frieze or mouldings, or in lines, bands and other forms of painted ornamentation, and, if necessary, the whole of the decoration might be heightened by gilding.
Coloured decoration on coloured grounds.—The use of coloured grounds, and especially those of contrasting colours, postulates the more complex forms of polychromatic decoration, where a good number of widely separated tints and shades of various colours are employed in any one scheme.
In polychromatic schemes of colouring there are certain laws which must be respected, regarding the relation of one colour to another, their modification of tint or shade, as affected by their position, and the strength or weakness of the light which illuminates them, however much may be left to the good taste and feeling for colour which the decorator may possess. All these essentials have to be considered, for it is not so much a question of rich and glowing colour schemes, or sober, quiet and subdued arrangements, but to obtain a harmonious colour finish in either. The decorator must aim for, and if possible obtain, a proper balance of colour, not so much for the achievement of uniformity, as for that of unity and repose. In order to obtain unity he must therefore see that even in the most complex polychromy a perfect balance of the colours is the first consideration, and of the utmost importance. In decoration we have both colour and form, but colour in decorative art is the more important of the two. A certain balance is looked for in ornamental or pictorial fillings of panels, for example, or even in the secondary ornamentation of painted bands, stiles, and other minor surfaces, but the repetition of exactly similar forms on such surfaces is by no means essential, but on the contrary produces monotony. In the matter of colour the case is reversed, for it is very important that there should be a decided repetition of
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[Victoria and Albert Museum.
Plate 12. From the Cartoon of the Mosaic in St. Paul’s Cathedral.