Use of float glass at Crystal Palace railway station, London

Float glass is a sheet of glass made by floating molten glass on a bed of molten tin. Crystal Palace railway station is in the London Borough of Bromley in south London. London ( ˈlʌndən is the capital and largest urban area in the United Kingdom. Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many Tin is a Chemical element with the symbol Sn (stannum and Atomic number 50 This method gives the sheet uniform thickness and very flat surfaces. Modern windows are made from float glass. GlassWindowjpg|thumb|right|190px|A stained glass panel depicting Biblical scenes at a historic church in Scotland]] A window is an opening Most float glass is soda-lime glass, but relatively minor quantities of specialty borosilicate^[1] and flat panel display glass are also produced using the float glass process. Soda-lime glass, also called soda-lime-silica glass, is the most prevalent type of Glass, used for windowpanes and glass containers (bottles and jars Borosilicate glass is a type of Glass with the main glass-forming constituents Silica and Boron oxide. Flat panel displays encompass a growing number of technologies enabling video displays that are lighter and much thinner than traditional television and video displays that use Cathode ^[2]

History

Old window containing a sheet of float glass in the upper left section, Jena, Germany. GlassWindowjpg|thumb|right|190px|A stained glass panel depicting Biblical scenes at a historic church in Scotland]] A window is an opening Jena (pronunciation ˈjeːna is a university City in central Germany on the river Saale. Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. The remaining sections are possibly not float glass as indicated by the distorted reflections of a tree.

In earlier centuries, window glass or flat glass was made by blowing large cylinders or large disks. Flat glass, sheet glass, or plate glass is a type of Glass, initially produced in plane form commonly used for Windows glass doors transparent Glassblowing is a glassforming technique that involves inflating the molten glass into a bubble or parison with the aid of the blowpipe or blow tube Cylinder blown sheet is a type of hand- blown window Glass. It is created with a similar process to Broad sheet, but larger cylinders are produced by swinging Crown glass was an early type of window glass In this process glass was blown into a "crown" or hollow globe The cylinders were cut open and flattened, and then panes were cut from the sheets. Most glass for windows up to the early 19th century was made from rondels, while most window glass during the 19th century was made using the cylinder method (these 'cylinders' were 6 to 8 feet (2 to 2. The 19th century of the Common Era began on January 1, 1801 and ended on December 31, 1900, according to the Gregorian calendar Cylinder blown sheet is a type of hand- blown window Glass. It is created with a similar process to Broad sheet, but larger cylinders are produced by swinging 5 m) long and 10 to 14 inches (250 to 350 mm) in diameter).

The first advances in automating glass manufacturing were patented in 1848 by Henry Bessemer, an English engineer. Sir Henry Bessemer ( January 19, 1813 – March 15, 1898) English Engineer and Inventor. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland An engineer is a person professionally engaged in a field of Engineering. His system produced a continuous ribbon of flat glass by forming the ribbon between rollers. This was an expensive process, as the surfaces of the glass needed polishing. If the glass could be set on a perfectly smooth body this would cut costs considerably. Attempts were made to form flat glass on a molten tin bath, notably in the US. Several patents were awarded, but this process was unworkable.

Before the development of float glass, larger sheets of plate glass were made by casting a large puddle of glass on an iron surface, and then polishing both sides, a costly process. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 From the early 1920s, a continuous ribbon of plate glass was passed through a lengthy series of inline grinders and polishers, reducing glass losses and cost.

Glass of lower quality, sheet glass, was made by drawing upwards from a pool of molten glass a thin sheet, held at the edges by rollers. As it cooled the rising sheet stiffened and could then be cut. The two surfaces were less parallel and of lower quality than those of float glass. This process continued in use for many years after the development of float glass.

Between 1953 and 1957, Sir Alastair Pilkington and Kenneth Bickerstaff of the UK's Pilkington Brothers developed the first successful commercial application for forming a continuous ribbon of glass using a molten tin bath on which the molten glass flows unhindered under the influence of gravity. Lionel Alexander Bethune Pilkington, ( 7 January, 1920 – 5 May, 1995) ( Sir Alastair Pilkington) and his associate Kenneth Bickerstaff Tin is a Chemical element with the symbol Sn (stannum and Atomic number 50 The success of this process lay in the careful balance of the volume of glass fed onto the bath, where it was flattened by its own weight. ^[3] Full scale profitable sales of float glass were first achieved in 1960.

Manufacture

Float glass is made by melting raw materials, typically consisting of sand, soda ash (sodium carbonate), dolomite, limestone, and salt cake (sodium sulfate). Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many Other materials may be used as colorants, refining agents or to adjust the physical and chemical properties of the glass. The goal of the glass technologist is to use a glass recipe for maximum glass yield, efficient use of plant assets, at minimal costs to achieve the best quality product.

The raw materials are mixed and fed into a furnace that is natural gas or fuel oil fired at 1500°C. Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, Fuel oil is a fraction obtained from Petroleum Distillation, either as a distillate or a residue Common flat glass furnaces are 9 m wide, 45 m long, and contain more than 1200 t of glass. The raw materials, referred to as batch, blend together to form a large pool of molten glass. Glass batch calculation or glass batching is used to determine the correct mix of raw materials (batch for a Glass melt The molten glass is fed into a bath of molten tin (about 3-4 m wide, 50 m long, 6 cm deep) through a delivery canal. Tin is a Chemical element with the symbol Sn (stannum and Atomic number 50 ^[4] The amount of glass allowed to pour onto the molten tin is controlled by a refractory gate called a tweel. A refractory is a material that retains its strength at high Temperatures ASTM C71 defines refractories as "non-metallic materials having those chemical and physical The tin bath is provided with a protective atmosphere consisting of a mixture of nitrogen and hydrogen to prevent oxidation of the tin. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state The glass flows out onto the tin surface forming a floating ribbon with perfectly smooth glossy surface on both sides with an even thickness of approximately 7 mm. Thinner glass is made by stretching the glass ribbon to achieve the proper thickness. Thicker glass is made by not allowing the glass pool to flatten to 7 mm. Machines called attenuators are used in the tin bath to control both the thickness and the width of the glass ribbon.

As the glass flows along the tin bath, the temperature is gradually reduced from 1100°C until the sheet can be lifted from the tin onto rollers at approximately 600°C. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature It then passes through the lehr where it is further cooled gradually so that it anneals without strain and does not crack from the change in temperature. A lehr is a temperature-controlled Kiln for annealing objects made of Glass. Annealing is a process of slowly cooling Glass to relieve internal stresses after it was formed The glass travels down the rollers in the lehr for about 100 meters and comes out at the "cold end" where it is cut by machines.

Some tin is absorbed into the glass, and with a proper ultraviolet light a sheen can be seen which differentiates the tin from the non-tin side. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays

Market

As of 2007, the world float glass market is dominated by the four companies: Asahi Glass, NSG/Pilkington, Saint-Gobain, and Guardian Industries. ( is a Japanese manufacturing company It is one of the core Mitsubishi companies ( is a Japanese Glass manufacturer In 2006 it purchased Pilkington of the United Kingdom Pilkington plc is the largest Glass manufacturer in the United Kingdom. Saint-Gobain SA ( is a French Multinational corporation, founded in 1665 in Paris and headquartered on the outskirts of Paris at La Other companies include PPG, Central Glass, Hankuk, Visteon, Cardinal Glass Industries. PPG Industries ( is an American manufacturer of Glass and Chemical products including automotive safety glass Visteon is an Automotive parts company spun off from the Ford Motor Company in 2000. ^[5]

See also

• Soda-lime glass, including composition and some properties of float glass
• Glass production
• Glass batch calculation

References and footnotes