Windows: A Book About Stained & Painted Glass

by Lewis F. Day

There is illustrated [opposite] a piece of Old Burmese incrusted decoration, a mosaic of white and coloured glass bound together by strips of metal, which, were it but clear instead of silvered at the back, would be precisely the same thing as an early mosaic window, even to the completion of the face by means of paint—of which more presently. In painted glass, on the other hand, the colour is not in the glass but upon it, more or less firmly attached to it by the action of the fire. A metallic colour which has some affinity with glass, or which is ground up with finely powdered glass, is used as a pigment, precisely as ceramic colours are used in pottery painting. The painted glass is then put into a kiln and heated to the temperature at which it is on the point of melting, whilst the colour actually does melt into it. By this means it is possible to paint a coloured picture upon a single sheet of white glass, as has been proved at Sèvres.

Strictly speaking, then, stained and painted glass are the very opposite one to the other. But in practice the two processes of glazing and painting were never kept apart. The very earliest glass was no doubt pure mosaic. It was only in our own day that the achievement (scientific rather than artistic) of a painted window of any size, independent of glazier’s work, was possible. Painting was at first always subsidiary to glazier’s work; after that, for a time, glazier and painter worked hand in hand upon equal terms; eventually the painter took precedence, and the glazier became ever more and more subservient to him. But from the twelfth to the seventeenth century there is little of what we call, rather loosely, sometimes “stained” and sometimes “painted” glass, in which there is not both staining and painting—that is to say, stained glass is used, and there is painting upon it. The difference is that in the earlier work the painting is only used to help out the stained glass, and in the later the stained glass is introduced to help the painting.

1. INCRUSTED GLASS MOSAIC, BURMESE (B. M.).
“Photo-Tint,” by James Akerman, London W. C.

That amounts, it may be thought, to much the same thing; and there does come a point where staining and painting fulfil each such an important part in the window that it is difficult to say which is the predominating partner in the concern. For the most part, however, there is no manner of doubt as to which practice was uppermost in the designer’s mind, as to the idea with which he set out, painting or glazing; and it makes all the difference in the work—the difference, for example, between a window of the thirteenth century and one of the sixteenth, a difference about which a child could scarcely make a mistake, once it had been pointed out to him.

Here perhaps it will be as well to describe, once for all, the making of a mosaic window, and the part taken in it by the glazier and the painter respectively. It will be easier then to discriminate between the two processes employed, and to discuss them each in relation to the other.

The actual construction of an early window is very much like the putting together of a puzzle. The puzzle of our childhood usually took the form of a map. It has occurred to me, therefore, to show how an artist working strictly after the manner of the thirteenth century—the period, that is to say, when painting was subsidiary to glazing—would set about putting into glass a map of modern Italy. In the first place, he would draw his map to the size required. This he would do with the utmost precision, firmly marking upon the paper (the mediæval artist would have drawn directly on his wooden bench) the boundary line of each separate patch of colour in his design. Then, according to the colour each separate province or division was to be, he would take a separate sheet of “pot-metal” and lay it over the drawing, so as to be able to trace upon the glass itself the outline of such province or division. That done, he would proceed to cut out or shape the various pieces of glass to the given forms. In the case of a simple and compact province, such as Rome, Tuscany, Umbria ([overleaf]), that would be easy enough. On the other hand, a more irregular shape, say the province of Naples, with its promontories, would present considerable difficulties—difficulties practically insuperable by the early glazier, to whom the diamond as a cutting instrument was unknown, and whose appliances for shaping were of the rudest and most rudimentary.

If with the point of a red-hot iron you describe upon a sheet of glass a line, and then, taking the material between your two hands, proceed to snap it across, the fracture will take approximately the direction of the line thus drawn. That is how the thirteenth century glazier went to work, subsequently with a notched iron instrument, or “grozing iron” as it was called, laboriously chipping away the edges until he had reduced each piece of glass to the precise shape he wanted.

It will be seen at once that the simpler the line and the easier its sweep the more likely the glass would be to break clean to the line, whereas in the case of a jagged or irregular line there would always be great danger that at any one sharp turn in it the fracture would take that convenient opportunity of going in the way it should not. For example, the south coast of Italy would be dangerous. You might draw the line of the sole of the foot, but when it came to breaking the glass the high heel would be sure to snap off (there is a little nick there designed as if for the purpose of bringing about that catastrophe), and similarly that over-delicate instep would certainly not bear the strain put upon it, and would be bound to give way. It should be mentioned that even were such pieces once safely cut (which would nowadays be possible) the glass would surely crack at those points the first time there was any pressure of wind upon the window, and so the prudent man would still forestall that event by designing his glass as it could conveniently be cut, without attempting any tour de force, and strengthening it at the weak points with a line of lead, as has been done in the glass map [opposite]. There is a jutting promontory on the coast of Africa, which, even if safely cut, would be sure to break sooner or later at the point indicated by the dotted line.