If he ask, as artists will, why cannot he do just what he likes, and as he likes, the answer is: because glass was not made for him, and will only do what he wants on condition of his demands upon it being reasonable. He might find it pleasanter if the world revolved round him; but it does not. If he would make a window he must go the way of glass; and the way of glass is this:—
In the first place, it is mosaic. It may be a mosaic of white glass or of the pearly tints which go to make what is termed grisaille, in which case the leads which bind the glass together form the pattern, or, at all events, a feature in it. Or it may be of coloured glass, or of white and colour, in which case the glass forms the pattern, and the lead joints are more or less lost in the outline of the design.
If the pattern is in white upon a deep-coloured ground the lead joints crossing the pattern and not forming part of it are, as it were, eaten up by the spreading rays of white light, and, supposing them to be judiciously contrived, do not count for much. On the other hand, the lead joints crossing the coloured ground are lost in its depth. Advantage is taken of this to break up the ground more than would be necessary for convenience of glazing, or of strength when glazed, and so to get that variety of pot-metal upon which so much of the beauty of glass colour depends.
52. Plain Glazing, Early French.
To give satisfactory colour the best of pot-metal glass is essential. Structural conditions which a man is bound to take into account in his design are—that the shapes he draws must be such as can readily be cut by the glazier; that his lead joints must be so schemed as, where not lost in the glass, to form part of the design, strengthening, for example, the outlines; that his plan must at intervals include provision for substantial iron bars which shall not interfere with the drawing.
He must understand that each separate colour in his composition is represented by a separate piece of glass, cut out of a sheet of the required colour. There may, and should, however, be variety in it. A sheet of glass varies in depth of tone according to its thickness, which in the best glass is never even; moreover, it may be streaked or otherwise accidentally varied; and so considerable play of tint may be got in a well-selected piece of pot-metal. Should a tint be required which the palette of the glazier does not supply it may sometimes be obtained by leading up two thicknesses of glass together. This expedient is called “plating.”
