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Window Glass: A Little History

In 1688, in France, a new process was developed for the production of plate glass, principally for use in mirrors, whose optical qualities 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, low melting metal, high-quality mirrors could be produced.

France also took steps to promote its own glass industry and attract glass experts from Venice; not an easy move for Venetians keen on exporting their abilities and know-how, given the history of discouragement of such behaviour (at one point, Venetian glass craftsmen faced death threats if they disclosed glassmaking secrets or took their skills abroad). The French court, for its part, placed heavy duties on glass imports and offered Venetian glassmakers a number of incentives: French nationality after eight years and total exemption from taxes, to name just two.

From craft to industry

It was not until the latter stages of the Industrial Revolution, however, 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 modern glass research was the German scientist Otto Schott (1851-1935), who used scientific methods to study the effects of numerous chemical elements on the optical and thermal properties of glass. In the field of optical glass, Schott teamed up with Ernst Abbe (1840-1905), a professor at the University of Jena and joint owner of the Carl Zeiss firm, to make significant technological advances.

Another major contributor in the evolution towards mass production was Friedrich Siemens, who invented the tank furnace. This rapidly replaced the old pot furnace and allowed the continuous production of far greater quantities of molten glass.

Increasing automation

Towards the end of the 19th century, the American engineer Michael Owens (1859-1923) invented an automatic bottle blowing machine which only arrived in Europe after the turn of the century. Owens was backed financially by E.D.L. Libbey, owner of the Libbey Glass Co. of Toledo, Ohio. By the year 1920, in the United States, there were around 200 automatic Owens Libbey Suction Blow machines operating. In Europe, smaller, more versatile machines from companies like O'Neill, Miller and Lynch were also popular.

Added impetus was given to automatic production processes in 1923 with the development of the gob feeder, which ensured the rapid supply of more consistently sized gobs in bottle production. Soon afterwards, in 1925, IS (individual section) machines were developed. Used in conjunction with the gob feeders, IS machines allowed the simultaneous production of a number of bottles from one piece of equipment. The gob feeder-IS machine combination remains the basis of most automatic glass container production today.

Modern flat glass technology

In the production of flat glass (where, as explained earlier, molten glass had previously been poured onto large tables then rolled flat into "plates", cooled, ground and polished before being turned over and given the same treatment on the other surface), the first real innovation came in 1905 when a Belgian named 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.

Around the end of the First World War, another Belgian engineer Emil Bicheroux developed a process whereby the molten glass was poured from a pot directly through two rollers. Like the Fourcault method, this resulted in glass with a more even thickness, and made grinding and polishing easier and more economical.

An off-shoot of evolution in flat glass production was the strengthening of glass by means of lamination (inserting a celluloid material layer between two sheets of glass). The process was invented and developed by the French scientist Edouard Benedictus, who patented his new safety glass under the name "Triplex" in 1910.

In America, Colburn developed another method for drawing sheet glass. The process was further improved with the support of the US firm Libbey-Owens and was first used for commercial production in 1917.

The Pittsburgh process, developed by the American Pennvernon and the Pittsburgh Plate Glass Company (PPG), combined and enhanced the main features of the Fourcault and Libbey-Owens processes, and has been in use since 1928.

The float process developed after the Second World War by Britain's Pilkington Brothers Ltd., and introduced in 1959, 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 into the annealing lehr.

Empire Windows has continually kept up with glass and technology and for over 40 years has provided its customers with the best and most up-to-date products on the market.