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glass - the amazing material

you can see through it, drink from it, and play marbles with it. it is one of the most common materials on earth and has been used by people for over 5,000 years.

the earliest man-made glass dates back to 4,000 b. c. no one knows for sure who made the first glass. the roman historian livy tells the story of some phoenician sailors who accidentally created this unique material. it seems the sailors were camping one night on a beach. they lit a fire and put their cooking pots on blocks of soda, which was the cargo their ship was carrying. the next morning, they found that the heat from the fire had fused the sand and soda into glass. sand, or silica, is still the main ingredient used to make glass today.

whether or not livy's story about the sailors is true, we do know that people were creating glass beads around 4,000 b. c. these beads were most often used as jewelry. people learned to make hollow glass objects around 1,500 b. c. the earliest method used to produce hollow objects was core-holding. a small ball of clay and dung was attached to a metal rod. then the ball was dipped into melted glass. as the glass cooled and hardened, the core was picked out, leaving a hollow object.

the syrians taught the egyptians how to make beads and small bottles from glass. glass bottles were found in the tomb of thutmose i of egypt. we know that thutmose i rules as pharaoh from 1507 b. c. to 1497 b. c. the bottles found in his tomb are less than five inches tall they are blue and decorated with yellow glass threads. glass was as popular as gemstones at this time and was often used in art objects as decoration.

around 300 b. c. the greeks learned to use a blow pipe to produce larger and more useful glass vessels. the introduction of the blowing iron was probably the most important step in the manufacture of glass.

the romans began making plate glass for mosaics and wall decorations in 100 b. c. they invented mirrors by coating flat glass with silver or gold foil. the romans also used a mold to contain and shape blown glass.

later, the romans made cameo glass, which was worth more than gold or jewels. in cameo glass, layers of different colored glass are fused together and carved, a process which leaves contrasting motifs in relief on the outside of the object. the most famous example of roman cameo glass is the portland vase, made in the first century, a. d. it can be seen at the british museum in london. the portland vase was created by blowing blue glass inside a vessel made of opaque white glass. then the design was marked on the outside of the vase. the artist ground away areas of the white glass, revealing the blue glass underneath and forming the design.

about 500 years ago, the glass-making industry began to flourish in venice, italy. for three hundred years, the venetians dominated the world's glass market. they developed a highly refined hard-soda glass that was colorless and highly transparent. this new glass became very popular and was in high demand all over the civilized world. despite the venetian laws, which under the penalty of death, forbade glass workers to leave venice or reveal the secrets of their glass making to anyone, some glass makers did leave italy.

glass making became america's first industry when settlers in jamestown began manufacturing glass in 1608. in 1675 an englishman named george ravenscroft revolutionized the glass industry. he added lead oxide to his recipe and produced a glass that was strong, brilliant, heavy, and easy to work with. his new recipe became the basis for english lead crystal, a very expensive and high-quality glass. ravenscroft's discovery also led to the later development of lenses, microscopes, and telescopes.

until the industrial revolution, glass making was a time-consuming and labor-intensive pursuit. all that changed during the industrial revolution. in 1903 the automatic bottle machine was invented. the bottle machine made it possible to mass produce bottles and jars of uniform height, weight, and capacity. high-speed filling and packing machines soon followed, and glass containers became commonplace in homes everywhere.

today glass is used to package many products that we use every day. in addition to being a much-used material, glass is friendly to the environment. glass is 100 percent recyclable, meaning that all of a glass container can be re-melted and used over and over again. the recycling potential for glass is limitless.

thus, this material, first created by nature and used by people for over 5,000 years, may solve some of the waste management problems facing humankind in the 21st century and beyond.
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