Architectural glass is glass that is used as a building material. It is most typically used as transparent glazing material in the building envelope, including windows in the external walls. Glass is also used for internal partitions and as an architectural feature. When used in buildings, glass is often of a safety type, which include reinforced, toughened and laminated glasses.
History
Timeline of modern architectural glass development
1226: "Broad Sheet" first produced in Sussex. 1330: "Crown glass" for art work and vessels first produced in Rouen, France. "Broad Sheet" also produced. Both were also supplied for export. 1500s: A method of making mirrors out of plate glass was developed by Venetian glassmakers on the island of Murano, who covered the back of the glass with a mercury-tin amalgam, obtaining near-perfect and undistorted reflection. 1620s: "Blown plate" first produced in London. Used for mirrors and coach plates. 1678: "Crown glass" first produced in London. This process dominated until the 19th century. 1843: An early form of "float glass" invented by Henry Bessemer, pouring glass onto liquid tin. Expensive and not a commercial success. 1874: Tempered glass is developed by Francois Barthelemy Alfred Royer de la Bastie (1830–1901) of Paris, France, by quenching almost molten glass in a heated bath of oil or grease. 1888: Machine-rolled glass introduced, allowing patterns. 1898: Wired-cast glass first commercially produced by Pilkington for use where safety or security was an issue. 1959: Float glass launched in UK. Invented by Sir Alastair Pilkington.
Cast glass
Glass casting is the process in which glass objects are cast by directing molten glass into a mould where it solidifies. The technique has been used since the Egyptian period. Modern cast glass is formed by a variety of processes such as kiln casting, or casting into sand, graphite or metal moulds. Cast glass windows, albeit with poor optical qualities, began to appear in the most important buildings in Rome and the most luxurious villas of Herculaneum and Pompeii.
Crown glass
One of the earliest methods of glass window manufacture was the crown glass method. Hot blown glass was cut open opposite the pipe, then rapidly spun on a table before it could cool. Centrifugal force shaped the hot globe of glass into a round, flat sheet. The sheet would then be broken off the pipe and trimmed to form a rectangular window to fit into a frame.
At the center of a piece of crown glass, a thick remnant of the original blown bottle neck would remain, hence the name "bullseye". Optical distortions produced by the bullseye could be reduced by grinding the glass. The development of diaper latticed windows was in part because three regular diamond-shaped panes could be conveniently cut from a piece of Crown glass, with minimum waste and with minimum distortion.
This method for manufacturing flat glass panels was very expensive and could not be used to make large panes. It was replaced in the 19th century by the cylinder, sheet, and rolled plate processes, but it is still used in traditional construction and restoration.
Cylinder glass
In this manufacturing process, glass is blown into a cylindrical iron mould. The ends are cut off and a cut is made down the side of the cylinder. The cut cylinder is then placed in an oven where the cylinder unrolls into a flat glass sheets.
Drawn Sheet glass (Fourcault process)
Drawn Sheet glass was made by dipping a leader into a vat of molten glass then pulling that leader straight up while a film of glass hardened just out of the vat – this is known as the Fourcault process. This film or ribbon was pulled up continuously held by tractors on both edges while it cooled. After 12 metres or so it was cut off the vertical ribbon and tipped down to be further cut. This glass is clear but has thickness variations due to small temperature changes just out of the vat as it was hardening. These variations cause lines of slight distortions. This glass may still be seen in older houses. Float glass replaced this process.
Irving Wightman Colburn development a similar method independently. He began experimenting with the method in 1899, and started production in 1906. He went bankrupt, but was bought by Michael Joseph Owens. Because the method was imperfect, they kept refining it till 1916 when they felt it was perfect, and opened a glass factory based on the technology the year after.