glass

glass. Semi- or fully transparent hard, brittle, lustrous material made by igneous fusion of silica (usually sand) with an alkaline sodium or potassium salt and added ingredients, such as lime, alumina, lead oxide, etc. Colour may be added by the addition of metallic oxides. It appears to have come into use for glazing the windows of grander buildings during the Roman Empire. In the Middle Ages coloured and painted glass, used in small pieces because of the difficulties of manufacturing larger expanses, was set in lead cames, commonly in churches: surviving examples (e.g. Chartres Cathedral, King's College Chapel, Cambridge, and Fairford, Glos.) are among the glories of medieval art. Glass used for domestic architecture also had to be set in lead cames or in sashes subdivided by glazing-bars.

Types of glass include:acid-etched: glass treated with wax or a similar substance into which a design is cut, then subjected to action by hydrofluoric acid which etches into the unprotected surface to create a design. Much used from Victorian times for decorative windows for public-houses, etc.;armourplate: thick toughened polished plate glass used for large windows, doors, etc.;broad: glass blown in cylinders which are then cut open and flattened, called muff or window-glass;Crown: blown from a glass tube into a bulb then opened and spun rapidly, the outer part thin, clear, and lustrous, but the centre or hub of thick glass (bottle, bullion, or bull's eye) largely opaque and never used for good work. It was the commonest type of glass found in British domestic architecture until the mid-1830s;flint: made from white sand, potash, nitre, red lead, and ground window-glass, used where refraction is desired, as on decorative altar-pieces, etc.;ground: with a rough surface, usually ground, to make it lose transparency;iridescent: with a coating to give it the appearance of the surface of a soap-bubble with rainbow colours;jealous: glass roughened to allow the light to pass through, but with a loss of transparency;laminated: toughened glass made by a laminated process;plate: poured on to a cast-iron table, rolled with a heavy roller, and polished on both sides;sheet: made by blowing into a cylinder of glass which increases in diameter before being cut lengthways, flattened, and polished. It was a refinement of broad or muff glass, invented by Messrs. Chance, near Birmingham (1832–8), and had a finish comparable to that of Crown glass, but cheaper and capable of being made in larger sheets, thus making glazing-bars in sashes obsolete;stained: coloured throughout its mass or with the colour applied or flashed. Crimson is produced with oxides of copper or tin, blue with cobalt, purple with manganese, and other colours using various combinations of chemicals;toughened: thick glass made in a variety of ways;wire: with a network of wire enclosed within it to improve security.Glass was used as a major component of external walls first in conservatories and green-houses, and then as a roofing material with glazing-bars of wood and, later, of iron. The evolution of railway termini and major exhibition buildings (such as Paxton's Crystal Palace, London (1851) ) developed the architectural possibilities of glass, leading to Dutert's Galerie des Machines, Paris (1889). Glazed curtain-walls were suggested by conservatories and used by architects such as Ellis, later developed by Behrens, Gropius, and others. Later developments have included solar-reflective and tinted glass for large expanses (as in Norman Foster's work), while blocks of glass, glass tubes, and glass slabs have been used widely in C20.

Bibliography

H. Blaser (1980);
Button & and Pye (1993);
Hix (1996);
Kohlmaier & and von Sartory (1986);
Koppelkamm (1981);
Korn (1967);
McGrath & and Frost (1937);
W. Papworth (1997);
Schild (1983);
Sturgis et al. (1901–2);
Wigginton (1996)