Art Glass
What is glass?
Most glass formulations contain about 70 –72% by weight of silicon dioxide (SiO2). The most common form of glass is soda-lime glass, which contains nearly 30% sodium and calcium oxides or carbonates. Pyrex is borosilicate glass containing about 10% boric oxide. Lead crystal is a form of glass that contains a minimum of 24% lead oxide, creating a much higher index of refraction than normal glass, and consequently much greater "sparkle". The presence of lead also makes the glass softer and easier to cut.
The major raw material of glass is sand (or "quartz sand") that contains almost 100% crystalline silica in the form of quartz. Although it is almost pure quartz, it may still contain a small amount (less than 1%) of iron oxides that would color the glass, so this sand is usually depleted before production to reduce the iron oxide amount to less than 0.05%. Large natural single crystals of quartz are pure silicon dioxide, and upon crushing are used for high quality specialty glasses. Synthetic amorphous silica, an almost 100% pure form of quartz, is the raw material for the most expensive specialty glasses.
A brief history of glass
Naturally occurring glass, such as obsidian, has been used since the stone age. Glass used as a glaze for pottery is known as early as 3000 BC. However, there is archaeological evidence to support the claim that the first glass was made in Mesopotamia. Glass beads, seals, and architectural decorations date from around 2500 BC. Glass was also discovered by Native Americans during the same time period.
The color of natural glass is green to bluish green. This color is caused by naturally occurring iron impurities in the sand. Common glass today usually has a slight green or blue tint, arising from these same impurities. Glassmakers learned to make colored glass by adding metallic compounds and mineral oxides to produce brilliant hues of red, green, and blue; the colors of gemstones. The earliest known beads from Egypt were made during the New Kingdom around 1500 BC and were produced in a variety of colors. They were made by winding molten glass around a metal bar and were highly prized as a trading commodity, especially blue beads, which were believed to have magical powers.
The oldest fragments of glass vases (evidence of the origins of the hollow glass industry), however, date back to the 16th century BC and were found in Mesopotamia. Hollow glass production was also evolving around this time in Egypt, and there is evidence of other ancient glassmaking activities emerging independently in Mycenae (Greece), China and North Tyrol.
Murano Glass
The center for glass making from the 14th century was the island of Murano, which developed many new techniques and became the center of a lucrative export trade in dinnerware, mirrors, and other luxury items. What made Venetian Murano glass significantly different was that the local quartz pebbles were almost pure silica and were ground into a fine clear sand that was combined with soda ash obtained from the Levant, for which the Venetians held the sole monopoly. The Venetian ability to produce this superior form of glass resulted in a trade advantage over other glass producing lands. Murano’s reputation as a center for glassmaking was born when the Venetian Republic, fearing fire might burn down the city’s mostly wood buildings, ordered glassmakers to move their foundries to Murano in 1291. Murano's glassmakers were soon the island’s most prominent citizens. Glassmakers weren't allowed to leave the Republic, however. Many craftsmen, however, took this risk and set up glass furnaces in surrounding cities and as far afield as England and the Netherlands.
Contemporary US Art Glass
In the past, the United States was never a great center of artistic glassblowing, but that has certainly changed. Now it is home to many of the worlds finest glass artists. Among the most famous and pivotal modern masters in the United States are Harvey Littleton (the founder of the American Studio Glass Movement), Dominic Labino, Dale Chihuly, & Richard Marquis.
Other well known glass artists in the US include Richard Satava, James Nowak, Milon Townsend (who is one of the best known flameworkers) and Craig Zweifel. Other US based glass artists, maybe not as well known, but equally talented, include Jeffery P'an, Peter Ridabock, Wes Hunting and Cathy Richardson.
Glass art is a fascinating field. The talent and skill of the individual glass blower can result in an amazing piece of art, or a piece that has to be discarded and started again from scratch.