Cummins Stehn Glossary

COMMONLY USED TERMS IN THE STAINED GLASS PROCESS

GLASS Naturally occurring material (obsidian) formed when silica is heated to 1720ºC. Not a metal, crystals or supercooled liquid but an amorphous solid.
MANUFACTURED GLASS

Mass produced glass manufactured by running a strip of molten clear glass between rollers, which leaves an imprinted pattern in the glass.

Cathedral Glass Mass produced glass manufactured by running a strip of molten clear glass between rollers, which leaves an imprinted pattern in the glass.

Mouth blown (Antique) glass

 Individually made sheets approx. 900 x 600mm made by mouth blowing an elongated balloon, cutting off the top and bottom, slitting the cylinder and flattening it. Excellent clarity and large colour range.
COLOURED GLASS Various mineral oxides are dissolved in the molten glass. More than 1000 colours possible.
POT GLASS Glass of one solid colour throughout the sheet.
FLASHED GLASS One layer of glass fused to another on one sheet: usually a dark coloured flash on a pale body eg blue on clear, red on blue, etc.
ACID ETCHING Use of hydrofluoric acid to remove the colour flash off flashed glass.
PLATING The placing of one piece of glass of the same shape on another of different colour and leading them together for special effect. Exquisitely subtle colours!
LEADLIGHTS Pieces of coloured glass held together by a matrix of H shaped leads, solder, putty and reinforcing support system.
STAINED GLASS The highly specialised and skilled art of painting on glass using kiln fired techniques. Now also, corruptly, a generic term for all coloured architectural glasswork.
GLASS PAINTS
Glass or Cathedral Paints Circa 1000 A.D. Powdered paint made of crushed glass, borax and metallic oxides, fused to the surface of the glass at 600ºC.
Stains Circa 1300 A.D. A chemical reaction at about 550ºC between silver applied to the surface of the glass and sodium in the glass, resulting in an exhilarating transparent yellow.
Enamels Circa 1500 A.D. Brightly coloured glass paints made from crushed, low melting glass, which is fused to the surface of the glass at 540ºC.
MEDIUMS All glass paints, stains and enamels come in powdered form and are mixed in liquid mediums to apply the paints. Some mediums are water, honey, glycerine, gum Arabic and lavender, clove and pine oils.
TRACE LINES The first strong lines of glass paint applied to the glass surface. Usually the piece of glass is placed over a lit, life size drawing (cartoon) and the line is traced from the drawing.
SHADE/MATTE FIRING A thin layer of paint applied over the trace lines, manipulated to render powerful shadows and exquisite textures to the subject. Lamentably this slowest and most skilful of techniques is all too frequently omitted.
STIPPLING A delicate form of shading, created by dabbing a brush’s bristles end on into the unfired paint and thereby admitting thousands of pinholes of light through the glass.
SPALL A chip or shell where the edge of a piece of glass hit and a sliver broken off.
ROUNDEL A circular piece of glass which is often exquisitely painted with fine detail.

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