The model for grisaille design was readily found in the earlier pattern work in plain glazing.
88. S. Jean-aux-Bois.
This last never quite went out of use. But already in the thirteenth century, and probably in the twelfth, it began to be supplemented, for the most part, by painting. The exceptionally graceful work at S. Serge, Angers, for example, on this page and the last, is probably not very much later than the year 1200. You can see at a glance how this is only a carrying further of the unpainted work in the same church ([page 27]) attributed to the thirteenth century. There may be found indeed amidst the plain glazing scraps of painted work; but they never happen to fit, and have pretty certainly found their way into the window in course of repairs. The unpainted window seems to be of greener and more silvery glass than the painted, to which perhaps the cross-hatching gives a rather horny look.
89. Soissons.
The one way of painting grisaille in the thirteenth century was to trace the design (which of course followed the traditional lines) boldly upon the white glass, and then to cross-hatch the ground, more or less delicately according to the scale of the work and its distance from the eye, as here shown. By this means the pattern was made to stand out clear and light against the background, which had now the value of a tint, only a much more brilliant one than could have been got by a film or wash of colour. Very occasionally a feature, such as the group of four crowns which form the centre of the circle, [above], might be emphasised by filling in the ground about them in solid pigment; but that was never done to any large extent. The rule was always to cross-hatch the ground.