The early examples show the influence of the Byzantine enamellers. The windows are filled with jewel-like patterns composed of small pieces of glass, enclosed with lead-lines, like the “cloisons” in cloisonné enamels. Gradually the figure subject becomes more pronounced; at first in comparatively small medallions set in a frame of tracery, then increasing in size until they become the leading motive. They are surmounted by canopies, enriched with ornament, as in the sculptured work of the period, and the character of the ornament reflects that of the carving. It is interesting to note that until the sixteenth century no use was made of painted glass. The material was what is known as “pot-metal”; that is to say, glass dyed with colour while in a condition of flux. The quality of these pieces of glass was translucent, permitting the passage of light, though not transparent. However, the deep red of ruby was so dense that the practice was adopted of fusing a layer of ruby on a layer of colourless glass and then of grinding away portions of the ruby, so as to brighten the mass by the contrast of white. In time this method of “flashing,” as it was called, was extended to other colours. Further, about the beginning of the fourteenth century it was discovered that a solution of silver applied to glass would under the action of the firing impart to it a “yellow stain.” Thus it was possible to infuse a yellow into the whole or parts of the colourless glass, and to introduce yellow into the “flashed” parts of blue and ruby, while the stain applied to greyish blue produced delicate tones of green. Another process was developed; namely, the use of enamel paint. A pigment composed of powdered coloured glass, mixed with some such binder as glue, was applied with a brush, after which the glass was subjected to a comparatively low degree of heat, sufficient to flux the pigment and fuse it into the body of the material. At first the only colour employed was brown, which being opaque in the firing was used for the line of the drawing. It was even used for shading, the paint being spread in gradations of thickness and, when dry, scraped off in parts or reduced to a stipple of tiny dots, by the action of a stiff brush. This process was also applied upon the yellow stain and comparatively colourless glass (_grisaille_) to produce diapers of pattern and other ornament.