Artisan glass refers to handblown or individually created glass items, as opposed to items such as standardized glass windows and other mass-produced products. Until a few hundred years ago, this description fit virtually all glass products.Common glass contains about 70% amorphous silicon dioxide, the same chemical composition as quartz and sand. Commercial glass can be made of pure silica, but usually sodium carbonate (soda) and calcium oxide (lime) are added. Various other additives are also used, such as lead to give glass more “sparkle.” Forms of glass that do not include silica as a major component are sometimes used for fiber optic cables and other specialized technical applications.Metals and metal oxides have long been used to give color to glass. Brilliantly colored cobalt blue glassware is a collectors’ item. Glass can also be colored with minerals including iron oxide (brown), chromium (green) , manganese (purple), selenium (pink or red), or combinations thereof. The method of heating and cooling the glass during its processing can significantly affect the colors produced by these compounds, in a process whose chemistry is complex and poorly understood.Lightning strikes which fuse sand can leave glass trails resembling tree roots along the path of the electrical discharge. Another naturally occurring glass, obsidian, has been used by humans since the stone age. The Phoenicians used glass as pottery glaze in 3000 BC, and glass beads, seals and architectural decorations found in Mesopotamia date back to 2500BC. The first glass was created by melting sand, producing a greenish product due to the naturally-occurring iron oxide in the sand. Even today, commercial glass has a slight green or blue tint, due to the presence of these same impurities. Egyptians made glass beads and glass bottles dating to 1500 BC. By 500 BC, glass-making technology had spread to Greece, and by 100 BC there were many glass-making centers around the Mediterranean. Window glass was quite commonly used in the area by 100 BC, such as thick, translucent samples found in Karanis, Egypt.The expansion of the Roman empire and widespread trade brought glass-making technology to Europe, the British Isles and China. After the fall of the Roman empire, their advanced glass-making technology fell out of use, and glass production declined until the seventh century, when Europeans once more began to revive the use of glass for a variety of purposes. The beautiful stained-glass windows on European cathedrals did not begin to be made until the 12th century.Venice developed into a glass-making center in the 14th century, and the city became the hub of a lucrative export trade in dinner ware, mirrors, beads, and other luxury items. Venetian glass was of unusually high quality because the local quartz stones used in its production were almost pure silica. These stones were ground into a fine clear sand which was blended with another locally occurring product called “Levant soda ash”, for which the Venetians held the sole monopoly. Even today, multicolored handmade glass beads are called “Venetian glass.”The Crown glass process of glass pane production was used up to the mid-1800s. A glassblower would spin around 9 pounds of molten glass at the end of a rod until it flattened into a disk approximately 5 feet in diameter, which was then cut into panes. Before float glass was invented, sheet glass was never completely uniform, and in historical buildings, some of these panes of slightly wavy glass can still be seen. In antique shops, it is still possible to find old apothecary bottles, each a slightly different size, produced by glass blowers.Around 1688, glass casting was introduced, leading glass to become a common, widely used material. The invention of the glass pressing machine in 1827 allowed the mass production of inexpensive glass articles. Handmade, irregular items are now strictly the purview of artists.
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