There should be no full realism of any kind.
No violent action must assert itself in a window.
I do not say that there must not, in any circumstances, be any violent action—the subject may demand it; but, if so, it must be so disguised by the craftsmanship of the work, or treated so decoratively, or so mixed up with the background or surroundings, that you do not see a figure in violent action starting prominently out from the window as you stand in the church. But, after all, this is a thing of artistic sense and discretion, and no rules can be formulated. The Parthenon frieze is of figures in rapid movement. Yet what repose! And in stained-glass
you must aim at repose. Remember,—it is an accessory to architecture; and who is there that does not want repose in architecture? Name me a great building which does not possess it? How the architects must turn in their graves, or, if living, shake in their shoes, when they see the stained-glass man turned into their buildings, to display himself and spread himself abroad and blow his trumpet!
Efface yourself, my friend; sink yourself; illustrate the building; consider its lines and lights and shades; enrich it, complete it, make people happier to be in it.
There must be no craft-jugglery in stained-glass.
The art must set the craft simple problems; it must not set tasks that can only be accomplished by trickery or by great effort, disproportioned to the importance of the result. But, indeed, you will naturally get the habit of working according to this rule, and other reasonable rules, if you yourself work at the bench—all lies in that.
There must be nothing out of harmony with the architecture.
And, therefore, you must know something
of architecture, not in order to imitate the work of the past and try to get your own mistaken for it, but to learn the love and reverence and joy of heart of the old builders, so that your spirit may harmonise with theirs.