18. Marble Mosaic, Roman.
Mediæval glaziers did not attempt anything like foliated ornament in leaded glass, and for good reason. In such work the difficulty of doing without lines detrimental to the design is greatly increased, whereas abstract forms you can bend to your will, as you can bend your strip of lead. The more natural the forms employed the more nature has to be considered in rendering them, and nature declines to go always in the direction of simple glazing. It might seem easy enough (to those who do not know the difficulty) to glaze together bits of heart-shaped green glass for leaves, and red for petals, with a dot of yellow for the eye of the flower, and to make use of the lead not only for outlines but for the stalks of the leaves and so on, all on a paler ground; but it is not so easy as that. The designer cannot go far without wanting other connecting leads (besides those used for the stalk); and when some leads are meant very emphatically to be seen and some to be ignored, there is no knowing what the actual effect may be: the drawing lines may be quite lost in a network of connecting leads. Again, the mediæval glazier did not, so far as we have any knowledge, build up in lead glazing a boldly pronounced pattern, light on dark or dark on light. This he might easily have done. On a small scale plain glazing must perforce be modest; but, given a scale large enough, almost any design in silhouette can be expressed in plain glazing. You may want in that case plenty of purely constructional leads, not meant to be seen, or in any case meant to be ignored; but if the contrast between design and background be only strong enough (say colour on white or white on colour), they do not in the least hurt the general effect. On the contrary, they are of the utmost use to the workman who knows his materials, enabling him to get that infinite variety of colour which is the crowning charm of glass.
19. Glass, Orvieto.
What the designer of leaded glass had to consider was, in the first place, the difficulty of shaping the pieces. That is now no longer very great, thanks to the diamond, which makes cutting so easy that there is even a danger lest the workman’s skill of hand may outrun his judgment, and tempt him to indulge in useless tours de force. The absurdity of taking the greatest possible pains to the least possible purpose is obvious. The more important consideration is now, therefore, the substantiality of the window once made. Think of the force of a gale of wind and its pressure upon the window: it is tremendous; and glazing does not long keep a smooth face before it. Except there is a solid iron bar to keep it in place, it soon bulges inwards, and presents a surface as undulous, on a smaller scale, as the pavement of St. Mark’s; and, as it begins to yield, snap go the awkwardly shaped pieces of glass which the glazier has been at such pains to cut. The mediæval artist, therefore, exercised no more than common sense, when he shaped the pieces of glass he employed with a view to security, avoiding sharp turns or elbows in the glass, or very long and narrow strips, or even very acutely pointed wedge-shaped pieces. No doubt the difficulty of cutting helped to keep him in the way he should go; probably, also, he was under no temptation to indulge in pieces of glass so large that, incapable of yielding, they were bound to break under pressure of the wind. That he sometimes used pieces so small as in time to get clogged with dust and dirt, was owing to the natural desire to use up the precious fragments which, under his clumsy system of cutting, must have accumulated in great quantity. Where most he showed his mastery was, in foreseeing where the strain would come, and introducing always a lead joint where the crack might occur, anticipating and warding off the danger to come. He was workman enough frankly to accept the limitations of his trade. Occasionally (as at Bonlieu) he may have shirked work; but he accommodated himself to the nature of his materials. Never pretending to do what he could not, he betrayed neither its weakness nor his own.
Mere glazing has here been discussed at a length which perhaps neither existing work of the kind nor the modern practice of the craft (more is the pity) might seem to demand. It is the most modest, the rudest even, of stained glass; but it is the beginning and the foundation of glass window making, and it affects most deeply even the fully developed art of the sixteenth century.
The leading of a window is the framework of its design, the skeleton to be filled out presently and clothed in colour; and, if the anatomy is wrong, nothing will ever make the picture right. The leads are the bones, which it is necessary to study, even though they were intrinsically without interest, for on them depends the form which shall eventually charm us. Beauty is not skin deep: it is the philosophy of the poet which is shallow.