5. Arab Lattice, Geometric.
That may appear at the first mention strange, considering what has been said about the absolute divergence between mosaic and enamelled glass. But it must be remembered that enamelling itself among the Lombard Franks, the Merovingians, and the Anglo-Saxons, was a very different thing from what the Limousin made it in the sixteenth century. It was, in fact, a quite different operation, the only point in common between the two being that they were executed in vitreous colour upon a metal ground. The enamel referred to as having probably influenced the early glazier is of the severer kinds familiar in Byzantine work, and known as champlevé and cloisonné. In the one, you know, the design is scooped out of the metal ground, in the other its outline is bent in flat wire and soldered to the ground. In either case the resulting cells are filled with coloured paste, which, under the action of the fire, vitrifies and becomes embodied with the metal. In champlevé enamel naturally the metal ground is usually a distinguishing feature. In cloisonné the ground as well as the pattern is, of course, in enamel; but in either case the outlines, and, indeed, all drawing lines, are in metal. In cloisonné enamel the metal “cloisons,” as they are called, fulfil precisely the function of the leads in glass windows; and it would have been more convenient to have left altogether out of account the sister process, were it not that, in the painting of quite early glass, the strokes with which the lines of the drapery and suchlike are rendered, bear quite unmistakable likeness to the convention of the Byzantine worker in champlevé. For that matter, one sees also in very early altar-pieces painted on wood, where gold is used for marking the folds of drapery, the very obvious inspiration of Byzantine enamel—but that is rather by the way.
The popular idea of an early window is that of a picture, or series of pictures, very imperfectly rendered. It may much more justly be likened to a magnified plaque of Byzantine enamel with the light shining through it. The Byzantine craftsman, or his descendants, at all events, did produce, in addition to the ordinary opaque enamel, a translucent kind, in imitation presumably of precious stones; and it might very well be that it was from thence the glazier first derived the idea of coloured windows. Quite certainly that was nearer to his thoughts than any form of painting, as we understand painting nowadays; and, what is more, had he aimed deliberately at the effect of enamel (as practised in his day), he could not have got much nearer to it. His proceeding was almost identical with that of the enamel worker. In place of vitreous pastes he used glass itself; in place of brass, lead; and, for supplementary detail, in place of engraved lines, lines traced in paint. Side by side with the early European window glazing, and most likely before it, there was practised in the East a form of stained glass window building of which no mention has yet been made. In the East, also, windows were from an early date built up of little pieces of coloured glass; but the Mohammedan law forbidding all attempt at pictorial representation of animate things, there was no temptation to employ painting; the glazier could do all he wanted without it. His plan was to pierce small openings in large slabs of stone, and in the piercings to set numerous little jewels of coloured glass. The Romans, by the way, appear also to have sometimes filled window spaces with slabs of marble framing discs of coloured glass, but these were comparatively wide apart, more like separate window-lets, each glazed with its small sheet of coloured glass. The Oriental windows, on the contrary, were most elaborately designed, the piercings taking the form of intricate patterns, geometric or floral. Sometimes the design would include an inscription ingeniously turned to ornamental use after the manner of the Moorish decorators of the Alhambra ([page 15]). A further development of the Oriental idea was to imbed the glass in plaster, a process easy enough before the plaster had set hard. This kind of thing is common enough in Cairo to this day, and specimens of it are to be found at the South Kensington Museum.
6. Arab Lattice, Floral.
M. Vogué illustrates in his book, La Syrie Centrale, an important series of windows in the Mosque of Omar (Temple of Jerusalem), erected in 1528, by Sultan Soliman. The plaster, says M. Vogué, was strengthened by ribs of iron and rods of cane imbedded in the stouter divisions of the framework, a precaution not necessary in the smaller Cairene lattices (measuring as a rule about four superficial feet), in which the pattern is simply scooped out of the half-dry plaster.
The piercings in these Oriental windows and window lattices are not made at right angles to the slab of stone or plaster, but are cut through at an angle, varying according to the position and height of the window, with a view to as little interference as possible with the coloured light. The glass, however, being fixed nearest the outside of the window, there is always both shadow and reflection from the deep sides of the openings, much to the enhancement of the mellowness and mystery of colour. In the Temple windows referred to, still further subtlety of effect is arrived at by an outer screen or lattice of faïence. Thus subdued and tempered, even crude glass may be turned to beautiful account.