[glas, glahs]
Glass, Carter, 1858-1946, American politician, U.S. Secretary of the Treasury (1918-20), U.S. Senator from Virginia (1920-46), b. Lynchburg, Va. He learned the printer's trade and became owner of the Lynchburg Daily News and Daily Advance. Glass became prominent in local politics, then served (1902-18) in the House of Representatives. As chairman of the House Committee on Banking and Currency, he was active in the framing of the Federal Reserve System. In 1918 he became Secretary of the Treasury under President Wilson, but in 1920 he resigned to become Senator from Virginia by appointment. Elected Senator for the balance of the term, he was reelected four times, serving until his death. He violently opposed President Franklin Delano Roosevelt's monetary and New Deal policies, but supported Roosevelt's foreign policy.

See biography by R. Smith and N. Beasely (1939, repr. 1972).

Glass, Montague Marsden, 1877-1934, American humorist and playwright, b. England, educated at the College of the City of New York and at New York Univ. He won fame for his humorous delineations of American Jewish life and character, especially in the "cloak and suit trade." Potash and Perlmutter (1910) and Abe and Mawruss (1911) were both successful as magazine stories and later as plays.
Glass, Philip, 1937-, American composer, b. Baltimore. Considered one of the most innovative of contemporary composers, he was a significant figure in the development of minimalism in music. Glass attended the Juilliard School of Music (M.A., 1962) and studied (1964-66) with Nadia Boulanger in Paris. There he also met Indian musicians Ravi Shankar and Alla Rakha, whose music was to influence his own compositions strongly. In 1968 he formed the Philip Glass Ensemble, a small group that employs electronically amplified instruments. During the 1970s he became known for music that blended standard notation and tonality with electronics. These lengthy and highly rhythmic compositions employ a number of phrases that are repeated and slowly modified during the music's course. The purest form of this style is represented in the four-hour-long Music in 12 Parts (1971-74).

More traditional harmonies entered his work with the opera Einstein on the Beach (1976), which Glass wrote with Robert Wilson; a work introduced the minimalist style to a mass audience and paved the way for a wider acceptance of contemporary opera. The meditative Einstein is without narrative plot and blends light, image, and sound as well as dance, words, and music into a hypnotic whole. During the ensuing years Glass's work has become more complex and varied. His best-known works are his operas; Satyagraha (1980), Akhnaten (1984), The Fall of the House of Usher (1988), Hydrogen Jukebox (1990, a collaboration with Allen Ginsberg), The Voyage (1992), and La Belle et la Běte (1994, composed for Jean Cocteau's film) followed Einstein. Three had their American debuts in 2001—The Marriages between Zones 3, 4 and 5 (1997); the epic White Raven (1998), another collaboration with Robert Wilson; and the smaller-scale In the Penal Colony (2001), based on the Franz Kafka short story. Later operas are Galileo Galilei (2002); Waiting for the Barbarians (2005), based on a novel by J. M. Coetzee; and Appomattox (2007), which dramatizes the American Civil War's last weeks and its aftermath. Glass's other compositions include symphonies, concertos, string quartets, songs, and film scores. Glass's work has been extremely influential in the development of a new generation of composers.

See his Music by Philip Glass (1987); R. Kostelanetz, ed., Writings on Glass (1997); Philip Glass: Looking Glass (documentary, 2005).

glass, hard substance, usually brittle and transparent, composed chiefly of silicates and an alkali fused at high temperature.

Composition and Properties of Glass

Most glass is a mixture of silica obtained from beds of fine sand or from pulverized sandstone; an alkali to lower the melting point, usually a form of soda or, for finer glass, potash; lime as a stabilizer; and cullet (waste glass) to assist in melting the mixture. The properties of glass are varied by adding other substances, commonly in the form of oxides, e.g., lead, for brilliance and weight; boron, for thermal and electrical resistance; barium, to increase the refractive index, as in optical glass; cerium, to absorb infrared rays; metallic oxides, to impart color; and manganese, for decolorizing. The term "crystal glass," derived from rock crystal, was at first applied to clear, highly refractive glass; it has come to denote in the trade a high-grade, colorless glass and is sometimes applied to any fine hand-blown glass.

The Process of Glassmaking

The processes of glassmaking have remained essentially the same since ancient times. The materials are fused at high temperatures in seasoned fireclay containers, boiled down, skimmed, and cooled several hundred degrees; then the molten glass (called metal) is ladled or poured into molds and pressed, or is blown (sometimes into molds), or is drawn. The shaped glass is annealed to relieve stresses caused by manipulation, then is slowly cooled. The glass, formerly annealed on shelves in a melting furnace, is now usually carried on rollers through annealing ovens (lehrs).

Although today most hollow vessels such as light bulbs or containers are machine blown, fine ornamental hollow ware is still made by gathering a mass of glass at the end of a long, iron blowpipe, blowing it into a pear-shaped bulb, which is rolled on an oiled slab (marver), shaped with tools, and then reblown, often into a mold; the glass is reheated periodically in a small furnace (glory hole). It is finally transferred to an iron rod (punty) attached to the base of the vessel, and the lip is shaped and smoothed. Methods of decoration include cutting, copper-wheel engraving, etching with hydrofluoric acid, enameling, gilding, and painting.

Development of the Glass Industry

Humans have used glass since prehistoric times, at first fashioning small objects from natural glass such as obsidian, a volcanic glass, or from rock crystal, a colorless, transparent quartz whose brilliance and clarity are emulated in manufactured glass.

Ancient Glassmaking

The place and date of origin of manufactured glass are not known. The oldest known specimens of glass are from Egypt (c.2000 B.C.), where the industry was well established c.1500 B.C. Many varieties of glass were known during Roman times, including cameo glass, such as the Portland vase, and millefiore glass, produced from fused and molded bundles of thin glass rods of many colors. Glass was also used for window panes, mirrors, prisms, and magnifying glasses. Except for the work done in Constantinople, little is now known of the methods of glassmaking used in Europe from the fall of Rome until the 10th cent., when stained glass came into use.

Early European Glassmaking

Venice was the leader in making fine glassware for almost four centuries after the Crusades and attempted to monopolize the industry by strict control at Murano of glassworkers, who were severely penalized for betraying the secrets of the art. After the invention (c.1688) of a process for casting glass, France was for many years supreme in the manufacture of plate glass such as that used to line the Galerie des Glaces at Versailles. Late in the 17th cent. England began to make flint glass, whose lead oxide content imparted a brilliance and softness that made it suitable for cut glass.

Glassmaking in Colonial America

The first glass factory in America was built in 1608, and glass was carried in the first cargo exported to England. Although other glasshouses were operated in the colonies, especially in New Amsterdam, the first successful and enduring large-scale glasshouse was set up by the German-born manufacturer Caspar Wistar in New Jersey in 1739. Some of the finest colonial glassware was produced in the Pennsylvania glasshouses of the German-born manufacturer H. W. Stiegel.

Beginnings of the Modern Era

The invention of a glass-pressing machine (c.1827), used by the American manufacturer Deming Jarves in his Boston and Sandwich Glass Company (1825-88), permitted the manufacturing of inexpensive and mass-produced glass articles. Nevertheless, in the 19th and 20th cent., there has remained a sense of pride in individual craftsmanship. The American artist Louis C. Tiffany was responsible for the design and manufacture of an extraordinary iridescent glass used in a variety of objects in the late 1800s. Exceptionally fine blown glassware has been designed by such artists as René Lalique and Maurice Marinot in France, Edvard Hald and Simon Gate in Sweden, as well as Sidney Waugh in the United States.

Contemporary Applications of Glass

Glass has become invaluable in modern architecture, illumination, electrical transmission, instruments for scientific research, optical instruments, household utensils, and even fabrics. New forms of glass, new applications, and new methods of production have revolutionized the industry. Recently developed forms of glass include safety glass, which is usually constructed of two pieces of plate glass bonded together with a plastic that prevents the glass from scattering when broken; fiberglass, which is made from molten glass formed into continuous filaments and used for fabrics or for electrical insulation; and foam glass, which is made by trapping gas bubbles in glass to yield a spongy material for insulating purposes. Certain uses of glass are now being superseded by newly developed plastics.

See also window.


See G. O. Jones, Glass (2d ed. 1971); L. D. Pyle et al., Introduction to Glass Science (1972); R. H. Doremus, Glass Science (1973); I. Fanderlik, Optical Properties of Glass (1983); P. Bansal, Handbook of Glass Properties (1986).

A burning-glass is a large convex lens that can concentrate the sun's rays onto a small area, heating up the area and thus resulting in ignition of the exposed surface. They were used in 18th-century chemical studies for burning materials in closed glass vessels where the products of combustion could be trapped for analysis. The burning-glass was a useful contrivance in the days before electrical ignition was easily achieved. Burning mirrors achieve a similar effect by using reflecting surfaces to focus the light.


The technology of the burning-glass has been known since antiquity. Vases filled with water used to start fires were known in the ancient world, and metaphorical significance was drawn (by the early Church Fathers, for instance) from the fact that the water remained cool even though the light passing through it would set materials on fire. Burning lenses were used to cauterise wounds and to light sacred fires in temples. Plutarch refers to a burning mirror made of joined triangular metal mirrors installed at the temple of the Vestal Virgins. Aristophanes mentions the burning-lens in his play The Clouds (424 BC).

Archimedes, the renowned mathematician, was said to have used a burning glass (or more likely a large number of angled hexagonal mirrors) as a weapon in 212 BC, when Syracuse was besieged by Marcus Claudius Marcellus. The Roman fleet was supposedly incinerated, though eventually the city was taken and Archimedes was slain.

The legend of Archimedes gave rise to a considerable amount of research on burning-glasses and lenses until the late 17th century. Successful recreations have been performed by Anthemius of Tralles (6th century AD), Proclus (6th century) (who by this means purportedly destroyed the fleet of Vitellus besieging Constantinople), Ibn Sahl in his On Burning Mirrors and Lenses (10th century), Alhazen in his Book of Optics (1021), Roger Bacon (13th century), Giambattista della Porta and his friends (16th century), Athanasius Kircher and Gaspar Schott (17th century), the Comte du Buffon in 1740 in Paris, Ioannis Sakas in the 1970s in Greece, and others. Sakas was able to ignite a wooden boat at some distance in only seconds. Buffon, using only 48 small mirrors, was able to melt a 3 kilogram (six pound) tin bottle, and ignite wood from a distance of 46 meters (150 ft). These recreations show the plausibility of Archimedes' achievement.

The pop science TV program MythBusters attempted to model Archimedes' feat by using mirrors to ignite a small wooden boat covered with tar, with only partial success—they found it too difficult to focus light from their hand-held mirrors onto a point small enough to ignite the boat.

Recent excavations at the Viking harbor town of Fröjel, Gotland in Sweden have revealed a small number of rock crystal lenses known as the Visby lenses. These may have been made using pole-lathes. They have an imaging quality comparable to that of 1950s aspheric lenses. The Viking lenses effectively concentrate sunlight enough to ignite fires; however it is not known whether they were used for this purpose. Similar technology may have been used in ancient Ireland (the Liath Meisicith) and quite possibly ancient Egypt.

In 1796, during the French Revolution and three years after the declaration of war between France and Great Britain, Étienne-Gaspard Robert met with the French government and proposed the use of mirrors to burn the invading ships of the British Royal Navy. They decided not to take up his proposal.

Chapter 17 of William Bates' 1920 book Perfect Sight Without Glasses, in which the author argues that observation of the sun is beneficial to those with poor vision, includes a figure of somebody "Focussing the Rays of the Sun Upon the Eye of a Patient by Means of a Burning Glass." Needless to say, this is highly dangerous.

Current use

Solar furnaces are used in industry to produce extremely high temperatures without the need for fuel or large supplies of electricity. They employ a large parabolic array of mirrors (some facilities are several stories high) to focus light to a high intensity.


Further reading

  • Temple, Robert. The Crystal Sun, ISBN 0 7126 7888 3.

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