History of Glass
Early Times | Middle Ages | Early American Glass | Modern Glass Making
Early Times. Before people learned to make glass, they had found two forms of natural glass. When lightning strikes sand, the heat sometimes fuses the sand into long, slender glass tubes called fulgurites, which are commonly called petrified lightning. The terrific heat of a volcanic eruption also sometimes fuses rocks and sand into a glass called obsidian. In early times, people shaped obsidian into knives, arrowheads, jewelry, and money. We do not know exactly when, where, or how people first learned to make glass. It is generally believed that the first manufactured glass was in the form of a glaze on ceramic vessels, about 3000 B.C. The first glass vessels were produced about 1500 B.C. in Egypt and Mesopotamia. The glass industry was extremely successful for the next 300 years, and then declined. It was revived in Mesopotamia in the 700's B.C. and in Egypt in the 500's B.C. For the next 500 years, Egypt, Syria, and the other countries along the eastern shore of the Mediterranean Sea were glassmaking centers.
Early glassmaking was slow and costly, and it required hard work. Glass blowing and glass pressing were unknown, furnaces were small, the clay pots were of poor quality, and the heat was hardly sufficient for melting. But glassmakers eventually learned how to make colored glass jewelry, cosmetics cases, and tiny jugs and jars. People who could afford them—the priests and the ruling classes—considered glass objects as valuable as jewels. Soon merchants learned that wines, honey, and oils could be carried and preserved far better in glass than in wood or clay containers.
The blowpipe was invented about 30 B.C., probably along the eastern Mediterranean coast. This invention made glass production easier, faster, and cheaper. As a result, glass became available to the common people for the first time. Glass manufacture became important in all countries under Roman rule. In fact, the first four centuries of the Christian Era may justly be called the First Golden Age of Glass. The glassmakers of this time knew how to make a transparent glass, and they did offhand glass blowing, painting, and gilding (application of gold leaf). They knew how to build up layers of glass of different colors and then cut out designs in high relief. The celebrated Portland vase, which was probably made in Rome about the beginning of the Christian Era, is an excellent example of this art. This vase is considered one of the most valuable glass art objects in the world.
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The Middle Ages. Little is known about the glass industry between the decline of the Roman Empire and the 1200's. Glass manufacture had developed in Venice by the time of the Crusades (A.D. 1096-1270), and by the 1290's an elaborate guild system of glassworkers had been set up. Equipment was transferred to the Venetian island of Murano, and the Second Golden Age of Glass began. Venetian glass blowers created some of the most delicate and graceful glass the world has ever seen. They perfected Cristallo glass, a nearly colorless, transparent glass, which could be blown to extreme thinness in almost any shape. From Cristallo, they made intricate lacework patterns in goblets, jars, bowls, cups, and vases. In the 1100's and 1200's, the art of making stained-glass windows reached its height throughout Europe.
By the late 1400's and early 1500's, glassmaking had become important in Germany and other northern European countries. Manufacturers there chiefly produced containers and drinking vessels. Northern forms were heavier, sturdier, and less clear than Venice's Cristallo. During the late 1500's, many Venetians went to northern Europe, hoping to earn a better living. They established factories there and made glass in the Venetian fashion. A new type of glass that worked well for copper-wheel engraving was perfected in Bohemia (now part of the Czech Republic) and Germany in the mid-1600's, and a flourishing industry developed.
Glassmaking became important in England during the 1500's. By 1575, English glassmakers were producing Venetian-style glass. In 1674, an English glassmaker named George Ravenscroft patented a new type of glass in which he had changed the usual ingredients. This glass, called lead glass, contains a large amount of lead oxide. Lead glass, which is especially suitable for optical instruments, caused English glassmaking to prosper.
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Early American glass. The first factory in what is now the United States was a glass plant built at Jamestown, Virginia, in 1608. The venture failed within a year because of a famine that took the lives of many colonists. The Jamestown colonists tried glassmaking again in 1621, but an Indian attack in 1622 and the scarcity of workers ended this attempt in 1624. The industry was reestablished in America in 1739, when Caspar Wistar built a glassmaking plant in what is now Salem County, New Jersey. This plant operated until 1780.
Wistar is one of the great names of early American glass. The second great American glassmaker was Henry William Stiegel, also known by his nickname, "Baron" Stiegel. Stiegel made clear and colored glass, engraved and enameled glass, and the first lead glass produced in North America. A third important American glassmaker was John F. Amelung, who became best known for his elegant engraved glass.
Another important early American glass, Sandwich glass, was made by the Boston and Sandwich Glass Company, founded by Deming Jarves in 1825. It was long believed to be the first company in America to produce pressed glass. But the first was actually the Bakewell, Page, and Bakewell Company of Pittsburgh, Pennsylvania, which began to make pressed glass earlier in 1825. These two companies and many others soon made large quantities of inexpensive glass, both pressed and blown. Every effort was made to produce a “poor man's cut glass.” In lacy Sandwich, for example, glassmakers decorated molds with elaborate designs to give the objects a complex, lacelike effect.
In the early 1800's, the type of glass in greatest demand was window glass. At that time, window glass was called crown glass. Glassmakers made it by blowing a bubble of glass, then spinning it until it was flat. This process left a sheet of glass with a bump called a crown in the center. By 1825, the cylinder process had replaced the crown method. In this process, molten glass was blown into the shape of a cylinder. After the cylinder cooled, it was sliced down one side. When reheated, it opened up to form a large sheet of thin, clear window glass. In the 1850's, plate glass was developed for mirrors and other products requiring a high quality of flat glass. This glass was made by casting a large quantity of molten glass onto a round or square plate. After the glass was cooled, it was polished on both sides.
Bottles and flasks were first used chiefly for whiskey, but the patent-medicine industry soon used large numbers of bottles. The screw-top Mason jar for home canning appeared in 1858. By 1880, commercial food packers began to use glass containers. Glass tableware was used in steadily increasing quantities. The discovery of petroleum and the appearance of the kerosene lamp in the early 1860's led to a demand for millions of glass lamp chimneys. All these developments helped to expand the market for glass.
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Modern glassmaking. Changes in the fuel used by the glass industry affected the location of glass factories. In the early days when wood was used as fuel, glassworks were built near forests. By 1880, coal had become the most widely used fuel for glassmaking, and glassmaking operations were near large coal deposits. After 1880, natural gas became accepted as the perfect fuel for melting glass. Today, most glass manufacturing plants are near the major sales markets. Pipelines carry petroleum and natural gas to the glass plants.
After 1890, the development, manufacture, and use of glass increased rapidly. The science and engineering of glass as a material are now so much better understood that glass can be tailored to meet an exact need. Any one of thousands of compositions may be used. Machinery has been developed for precise, continuous manufacture of sheet glass, tubing, containers, bulbs, and a host of other products.
New methods of cutting, welding, sealing, and tempering, as well as better glass at lower cost, have led to new uses of glass. Glass is now used to make pipelines, cookware, building blocks, and heat insulation.
Ordinary glass turns brown when exposed to nuclear radiation, so glass companies developed a special nonbrowning glass for use in observation windows in nuclear power plants. More than 10 tons (9 metric tons) of this glass are used in windows in one nuclear power plant. In 1953, automobile manufacturers introduced fiberglass-plastic bodies. Today, such materials are used in architectural panels to sheathe the walls of buildings. They are also used to make boat hulls and such products as missile radomes (housings for radar antennas). Other types of glass have been developed that turn dark when exposed to light and clear up when the light source is removed. These photochromic glasses are used in eyeglasses that change from clear glasses to sunglasses when worn in sunlight.
During the late 1960's, glass manufacturers established collection centers where people could return empty bottles, jars, and other types of glass containers. The used containers are recycled—that is, broken up and then melted with silica sand, limestone, and soda ash to make glass for new containers. Glass can be recycled easily because it does not deteriorate with use or age. In addition to the collection centers, some communities have set up systems to sort glass and other reusable materials from regular waste pickups.
In the 1970's, optical fibers were developed for use as "light pipes" in laser communication systems. These pipes maintain the brightness and intensity of light being transmitted over long distances. Types of glass that can store radioactive wastes safely for thousands of years were also developed during the 1970's.
The late 1900's brought important new specialty glasses. Among the new specialty glasses were transparent glass ceramics, which are used to make cookware, and chalcogenide glass, an infrared-transmitting glass that can be used to make lenses for night vision goggles.
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• Steve W. Martin, Ph.D., Professor of Materials Science and Engineering, Iowa State University.
Steve W. Martin,
"Glass," Discovery Channel School, original content provided by World Book
worldbook/atozscience/g/225740.html, August 2001.
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