Associated with Mosaic decoration in the Byzantine Period was the employment of marble in shafts of columns and for lining walls by banding or slabbing, frequently quartered, so as to display the markings in reciprocal forms. Such marbles were chosen for figuring and colour, the former in its variety being an important factor in the surface interest.
Similar employment of slabs occurs in the treatment of floors, where contrast in colour is the chief consideration. It is sometimes associated with Mosaic of small tesseræ, also in marble, whereas that used on walls and in vaults was frequently of glass.
The foregoing is a broad summary of ornamental expression in the Flat, with the exception of Book Decoration.
In Black and White, which is chiefly employed, the designs may be in tone or line with suggestion of rotundity or relief; or line decoratively employed, according to subject, or purely decorative.
The same applies to renderings in colour. Designs for covers are controlled by the processes involved, whether printed, stamped or tooled.
[Illustration: No. 269. Mosaic Border, Roman.]
[Illustration: No. 270. Roman Mosaic. Woodchester, Gloucester.]
[Illustration: No. 271. Roman Mosaic. Treatment in Light and Shade suggestive of relief. (Photo: V & A Museum).]
[Illustration: No. 272. Tooled Bookbinding in Leather. Repetition due to tools or stamps. (Photo: V & A Museum).]
[Illustration: No. 273. Modelled Plaster, shewing relatively large ground area. (Photo: V & A Museum).]
[Illustration: No. 274. Wood Carving. Grinling Gibbons. Attention devoted to detail with elimination of ground. (Photo: V & A Museum).]
[Illustration: No. 275. Wood Carving. French, Louis XIV. (Photo: V & A Museum).]
In the two latter the ornament should be in profile or silhouette. In tooled bindings, repetition of unit or motif is essential, the design being the direct result of available tools.
In such bindings further interest may be imparted by gilding either the detail or by introducing gold as powdering on shapes or backgrounds, or by the so-called inlaying of other colours.
In Relief ornament, design and character should be the result of technical expression. If considered from an economic point of view, the tendency would naturally be to obtain the maximum effect with the minimum of labour; and this would invariably result, when the decoration is built up or applied to an existing ground as in modelled work, in slight occupation, with comparatively large intervals.