Author: Leslie Gilmour
Glass is naturally formed when certain types of rocks melt as a result of high-temperatures such as volcanic eruptions, lightning strikes or the impact of meteorites, and then cools and solidify rapidly.
According to Roman historians they became aware of the existence of glass accidentally in the region of Syria around 5000 BC. This short history looks at the birth and evolution of man-made glass and the new developments in smart glass.
Glass beads are thought to be the earliest man-made glass they were mainly opaque and are thought to date back to around 3500 BC. They have been found in Egypt and Eastern Mesopotamia. The oldest fragments of glass vases date back to 1600 BC and were found in Mesopotamia.
Egyptian craftsmen are thought to have begun developing a method for producing glass pots around 1500 BC by dipping a core mould of compressed sand into molten glass and then turning the mould so that molten glass adhered to it. There is not much evidence of further advancement until the 900 BC. Over the following 500 years glass production centred on Alessandria from where it is thought to have spread to Italy.
The first glassmaking manual dates back to around 650 BC. A major breakthrough in glassmaking was the discovery of glassblowing some time between 27 BC and AD 14, attributed to Syrian craftsmen. The long thin metal tube used in the blowing process has changed very little since then.
The Romans spread glassmaking technologies the result of their conquests. During the reign of the emperor Augustus, glass objects began to appear throughout Italy, in France, Germany and Switzerland. It was the Romans who began to use glass for architectural purposes, with the discovery of clear glass. Cast glass windows with poor optical qualities began to appear in the most important buildings in.
Archaeological excavations on the island of Torcello near Venice, Italy, have unearthed objects from the late 7th and early 8th centuries which bear witness to the transition from ancient to early Middle Ages production of glass.
Towards the years 1000 AD significant changes in European glassmaking techniques took place. Given the difficulties in importing raw materials, soda glass was gradually replaced by glass made using the potash obtained from the burning of trees.
The 11th century saw the development by German glass craftsmen of a technique – then further developed by Venetian craftsmen in the 13th century – for the production of glass sheets. By blowing a hollow glass sphere and swinging it vertically, gravity would pull the glass into a cylindrical “pod” measuring as much as 3 metres long, with a width of up to 45 cm. While still hot, the ends of the pod were cut off and the resultant cylinder cut lengthways and laid horizontal. The panes thus created would then be joined with lead strips and pieced together to create windows. Glazing remained, however, a great luxury up to the late Middle Ages, with royal palaces and churches the most likely buildings to have glass windows. Stained glass windows reached their height as the Middle Ages drew to a close.
In 1688, in France, a new method was developed for the production of plate glass, principally for use in mirrors, whose optical merits had, until then, left much to be desired. The molten glass was poured onto a special table and rolled out flat. After cooling, the plate glass was ground on large round tables by means of rotating cast iron discs and increasingly fine abrasive sands, and then polished using felt disks. The result of this plate pouring process was flat glass with good optical transmission qualities. When coated on one side with a reflective metal high-quality mirrors could be produced.
It was not until the later stages of the Industrial Revolution that mechanical technology for mass production and in-depth scientific research into the relationship between the composition of glass and its physical qualities began to appear in the industry.
A key figure and one of the forefathers of contemporary glass research was the German scientist Otto Schott, who used scientific methods to study the effects of various chemical elements on the optical and thermal properties of glass. In the field of optical glass, Schott teamed up with Ernst Abbe, to make important technological advances.
In the production of flat glass the first real innovation came in 1905 when a Belgian, (Fourcault), managed to vertically draw a continuous sheet of glass of a consistent width from the tank. Commercial production of sheet glass using the Fourcault process eventually got under way in 1914. An off-shoot of evolution in flat glass production was the strengthening of glass by means of lamination.
The float process developed after 1945 by Pilkington combined the brilliant finish of sheet glass with the optical qualities of plate glass.
Now glass production has taken another great leap forward, privacy glass is the newest and currently most upmarket glass available. With only a touch of a remote control or the turn of a dial the glass can be made to change opacity. New glass windows on office blocks can be set to let in less light as the sun becomes stronger saving on air-conditioning costs.
During the last 5500 years glass has come a long way and we just take it for granted now.
Source: articlesbase.com