The glass duly painted and burnt, the puzzle would be put together again on the bench, and bands of lead, grooved at each side to admit and hold the glass, would be inserted between the two pieces. These would be soldered together at the joints where two leads met; a putty-like composition or “cement” would be rubbed into the interstices between lead and glass to stiffen it, and make it air-and water-tight; and, that done, the window was finished.
It would only remain (what would in practice have been done before cementing) to solder to the leads at intervals sundry loose ends of copper-wire, eventually to be twisted round the iron saddle bars let into the stone framework of the window to support it; it would then be ready to be fixed in its place.
In contradistinction to the mosaic method of execution adopted by the thirteenth century glazier, a glass painter of the eighteenth century, and perhaps of the seventeenth, would, even though there were no necessity for longitudinal and latitudinal lines, cut up his window into oblong pieces of convenient size, only, of course, parallel and at right angles to one another.
The sea he might or might not glaze in blue glass; here and there perhaps, but not necessarily at all, an occasional province might be leaded in with a piece of pot-metal; but for the most part he would use panes of white glass, and rely for the colour of the provinces upon enamel. He would have no need to separate his enamel colours by a line of lead, and where he wanted a dividing line he would just paint it in opaque brown. This method of glass painting forms an altogether separate division of the subject, not yet under discussion. It is referred to here only by way of contrast, and to emphasise the fact that, though we are in the habit of using the term stained glass rather loosely—though a stained glass window is almost invariably helped out to some extent by painting (unless it be what is technically known as “leaded glass” or “plain glazing”), and though a painted window is seldom altogether innocent of glass that is stained—there are, as a matter of fact, two methods of producing coloured windows, the mosaic and the enamelled; and that however customary it may be to eke out either method by the other more or less, windows divide themselves into two broad divisions, according as it is pot-metal or enamel upon which the artist relies for his effect.
Between these two widely different ideals there are all manners and all degrees of compromise, and methods were employed which, to describe at this point, would only complicate matters. It will be my purpose presently to describe in detail the steps by which mere glazing developed into painted glass, and how painting came to supersede glazing; to show in how far painting was a help to the glazier, and in how far it was to his hurt; to describe, in short, the progress of the glass painter’s art, to better and to worse; and to distinguish, as far as may be, the principles which govern or should govern it.
3. Ancient Arab Window.