STAINED
GLASS

with its depth and translucency, owes its intrinsic qualities to metallic oxides, such as cobalt, giving fine blues, silver, pale and deep yellows, pink from iron and antimony, and ruby from gold and copper, which also yields fine greens. When these oxides are mixed with the glass, in its fused state, it is termed pot metal, but if the coloured oxides are applied to the surface of the glass only, it is termed flashed or cased glass. Ruby, owing to its depth of colour, is usually cased glass. Fine blues are often flashed, and splendid effects are produced by flashing ruby over yellow, or blue pot metal glass. Cased glass is of the greatest value owing to the variety of tint that can be produced on a single sheet of glass, and also that the colour may be removed by grinding or by the use of fluoric acid.

The rationale of the glass painter is—1st, The scheme of composition and colour shown on a small scale. 2nd, A full sized cartoon in charcoal or monochrome, with all the details carefully drawn, and showing the lead lines and positions of the iron stanchions for strengthening the window. 3rd, A tracing on cloth showing the lead lines only, called the cut line, on which is cut the selected pieces of glass. 4th, Tracing all details from the cartoon, with brown enamel on each piece of glass, the pieces after firing being then fixed in the leading, and kept together with H shaped leads. A diagram is given here showing the leading of an example of 13th century glass.

The brown enamel, which is used entirely for outline, detail or shading, is a fusible glass in combination with opaque manganic or ferric oxide, and tar oil. With this enamel, smear shading or stipple shading is worked. This may be removed as required, before firing, by means of a pointed stick or quill, so as to give the details of embroidery, or of heraldic forms.

Silver stain (oxide of silver) introduced at the beginning of the 14th century is largely used in stained glass, and usually on the back thereof. According to the different degrees of heat in the firing, a pale yellow or deep orange of great transparency is produced.

Coloured glass was made by the Egyptians 4000 years ago, but the earliest stained glass windows recorded, were those of Brionde A.D. 525. None however are known to be in existence prior to those of St. Denis A.D. 1108. Other examples are found in Norman windows, with small medallions of figures and ornament of a decided Byzantine type, extremely deep in colour, being, by its style of treatment, termed mosaic glass. The 13th century, or early Gothic period, has single lancet lights, with medallions containing small figures surrounded by the typical 13th century foliage; or the windows were entirely of ornament in grisaille, arranged symmetrically, having narrow bands of ruby or blue, with wide borders. These grisaille windows are of a greenish white glass, with the ornament in outline, and the ground hatched with brown enamel in fine cross lines (fig. 1-2).

“Quarry glass,” square or diamond in shape, with brown enamel details, was frequently used, where simple masses were desired.