• Robert W. Sowers

Stained glass, in the arts, the coloured glass used for making decorative windows and other objects through which light passes. Strictly speaking, all coloured glass is “stained,” or coloured by the addition of various metallic oxides while it is in a molten state. Nevertheless, the term stained glass has come to refer primarily to the glass employed in making ornamental or pictorial windows. The singular colour harmonies of the stained-glass windoware less due to any special glass-colouring technique itself than to the exploitation of certain properties of transmitted light and the light-adaptive behaviour of human vision. Rarely equalled and never surpassed, the great stained-glass windows of the 12th and early 13th centuries actually predate significant technical advances in the glassmaker’s craft by more than half a century. And much as these advances undoubtedly contributed to the delicacy and refinement of the stained glass of the later Middle Ages, not only were they unable to arrest the decline of the art, but they may rather have hastened it to the extent that they tempted the stained-glass artist to vie with the fresco and easel painter in the naturalistic rendition of their subjects.

Neither painting on stained glass nor its assembly with grooved strips of leading is an indispensable feature of the art. Indeed, the leaded window may well have been preceded by windows employing wooden or other forms of assembly such as the cement tracery that has long been traditional in Islamic architecture, and the single most important technical innovation in 20th-century stained glass, slab glass and concrete, was a variation on the earlier masonry technique.