26th October 2010

Short History of Glass Making

Glass making origins are buried in human prehistory. Most likely, early efforts were inspired by Obsidian, super-heated silica made as a natural byproduct of volcanic eruptions and prized by prehistoric societies for its beauty, sharp edges and workability. Lightning strikes in sandy soils can also create a form of natural glass called fulgurites. Furnace Jet for Float Glass Manufacture Man-made Glass There is evidence that intentional glass making in both Egypt and Mesopotamia occurred more than 6,000 years ago. Super-heated crushed quartzite sand was used to produce liquid, which then cooled clear and was commonly used to make glazes for ceramic vessels. 2,500 years ago, clear glass was being made with the addition of a soda-rich salt called natron, used as a flux (viscosity control), a process that passed into Europe and remained the dominant method of glass creation until around 800AD. Glass Artisans Glass-blowing, using human breath to modify glass by blowing through a pipe into the heated material emerged around the Mediterranean and moved throughout the Roman Empire during the 1st century BC. Commercial workshops producing blown vessels and windows in Italy, Israel, France and further afield had emerged with highly qualified and respected artisans in the 1st century AD. During the 12th century AD, glass makers in Venice transformed their process from the natron-based Roman technique to soda-ash based techniques. By the 15th Century, Venice was the major producer of glass in Europe. Venetian glass was so highly esteemed that artisans were forbidden to leave the Island of Murano in an attempt to protect their 'trade secrets'. The presence of iron in sand creates glass with a greenish colour tint, so white sand with exceptional purity was sought for superior clarity and transparency. Plate Glass In 1688, a new process was developed in France for the production of plate glass. Molten glass was poured onto a special table and rolled flat and ground after cooling by a variety of processes, leading to flat glass with good optical transmission qualities. The Industrial Revolution added mechanical technology for mass production and greater scientific research into optimal composition of glass and improved furnaces that dealt with far greater quantities of molten glass. Modern Technology In 1905, a Belgian, Emile Fourcault managed to vertically draw a continuous sheet of glass with a consistent width. Commercial production using the Fourcault process for sheet glass commenced in 1914. Another Belgian engineer, Emil Bicheroux, developed a process where molten glass was poured directly through two rollers, resulted in a more even thickness that made the finishing process more economical. Float Glass Introduced in 1959, the Float Process developed by Britain's Pilkington Brothers combined the brilliant finish of sheet glass with the optical qualities of plate glass. Molten glass, when poured across the surface of a bath of molten tin, spreads and flattens before being drawn horizontally in a continuous ribbon. Our GlassTalks blog post on Manufacturing Float Glass, picks up the modern story and the ongoing innovation in contemporary performance glass. Viridian Glass is Australia and New Zealand's leading producer of performance glass. <!--ddc677eb6bd9482b8bf596373c762bd3-->