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Encyclopedia > Architectural glass

Architectural glass has been used in buildings since the 11th century. Glass is typically used in buildings as a transparent glazing material for windows in the building envelope. Glass is also used in glazed internal partitions and as an architectural feature. Glass can be made transparent and flat, or into other shapes and colours as shown in this ball from the Verrerie of Brehat in Brittany. ... Glazing, in architecture, is a transparent part of a wall, usually made of glass or plastic (acrylic and polycarbonate). ...


Glass in buildings is often of a safety type, including toughened and laminated glasses.

Contents


Older styles of glass

The uneven surface of old glass is visible in the reflection on this window pane.
The uneven surface of old glass is visible in the reflection on this window pane.

Before the invention of the float glass method of manufacture, flat glass panels were generally made via the cylinder, sheet or rolled plate processes. Optical distortions could be reduced at substantial cost by grinding the glass to produce polished plate glass. Old glass showing distortions © 2004 Wyatt Greene File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Old glass showing distortions © 2004 Wyatt Greene File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...


Cylinder glass

Main article: Cylinder blown sheet and Machine drawn cylinder sheet. Cylinder blown sheet is a type of hand-blown window glass. ... Machine drawn cylinder sheet was the first mechanical method for drawing window 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 sheet. William J. Blenko used this method in the early 1900s to make stained glass. These imperfect panes have led to the misconception that glass is actually a high-viscosity liquid at room temperature, which is not the case. (See below.)


Sheet glass

Sheet glass (sometimes called window glass or drawn 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 film or ribbon was pulled up continuously held by tractors on both edges while it cooled. After 12 meters 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. You may still see this glass in older houses. Float glass replaced this process.


Rolled plate glass

The glass is taken from the furnace in large iron ladles, which are carried upon slings running on overhead rails; from the ladle the glass is thrown upon the cast-iron bed of a rolling-table; and is rolled into sheet by an iron roller, the process being similar to that employed in making plate-glass, but on a smaller scale. The sheet thus rolled is roughly trimmed while hot and soft, so as to remove those portions of glass which have been spoilt by immediate contact with the ladle, and the sheet, still soft, is pushed into the open mouth of an annealing tunnel or lehr, down which it is carried by a system of rollers.


Polished plate glass

Main article: Polished plate. Polished plate is a type of hand-blown glass. ...


The plate glass process starts with sheet or rolled plate glass. This glass is dimensionally inaccurate and often created visual distortions. These rough panes were ground flat then polished clear. This was a fairly expensive process.


Before the float process, mirrors were plate glass as sheet glass had visual distortions that were akin to those seen in amusement park or fun-fair mirrors.


Float (annealed) glass

Main article: Float glass. Float glass is made by melting raw materilas consisting of sand, limestone, soda ash, dolomite, iron oxide and salt cake. ...


90% of the world's flat glass is produced by the float glass process invented in the 1950s by Sir Alastair Pilkington of Pilkington Glass, in which molten glass is poured onto one end of a molten tin bath. The glass floats on the tin, and levels out as it spreads along the bath, giving a smooth face to both sides. The glass cools and slowly solidifies as it travels over the molten tin and leaves the tin bath in a continuous ribbon. The glass is then annealed by cooling in a temperature controlled oven called a "lehr". The finished product has near-perfect parallel surfaces. Float glass is made by melting raw materilas consisting of sand, limestone, soda ash, dolomite, iron oxide and salt cake. ... The 1950s were the decade that spanned the years 1950 through 1959, although some sources say from 1951 through 1960. ... Lionel Alexander Bethune Pilkington known as Sir Alastair Pilkington (1920_1995) was the inventor of Float glass. ... Pilkington Glass is a well-known British glass manufacturer. ... General Name, Symbol, Number tin, Sn, 50 Chemical series poor metals Group, Period, Block 14, 5, p Appearance silvery lustrous gray Atomic mass 118. ...


A very small amount of the tin is imbedded in the glass on the side it touched. The tin side is easier to make into a mirror. This "feature" quickened the switch from plate to float glass. The tin side of glass is also softer and easier to scratch.


Glass is produced in standard metric thicknesses of 2, 3, 4, 5, 6, 8, 10, 12, 15, 19 and 22 mm. Molten glass floating on tin in a nitrogen/hydrogen atmosphere will spread out to a thickness of about 6 mm and stop due to surface tension. Thinner glass is made by stretching the glass while it floats on the tin and cools. Similarly, thicker glass is pushed back and not permitted to expand as it cools on the tin. A millimetre (American spelling: millimeter, symbol mm) is an SI unit of length that is equal to one thousandth of a metre. ... In physics, surface tension is an effect within the surface layer of a liquid that causes the layer to behave as an elastic sheet. ...


Annealed glass is considered a hazard in architectural applications as it breaks in large, jagged shards that can cause serious injury. Building codes across the world restrict the use of annealed glass in areas where there is a high risk of breakage and injury, for example in bathrooms, in door panels, fire exits and at low heights in schools. The Parthenon on top of the Acropolis, Athens, Greece Architecture (from Latin, architectura and ultimately from Greek, αρχιτεκτων, a master builder, from αρχι- chief, leader and τεκτων, builder, carpenter) is the art and science of designing buildings and structures. ... A building code is a set of rules that specify the minimum acceptable level of safety for constructed objects such as buildings and nonbuilding structures. ... Risk is the potential impact (positive or negative) to an asset or some characteristic of value that may arise from some present process or from some future event. ... Injury is damage or harm caused to the structure or function of the body caused by an outside agent or force, which may be physical or chemical. ... A typical American bathroom A bathroom is a room that may have different functions depending on the cultural context it is used in. ... The front door of a house is often decorated to appear inviting. ... A fire escape is a fire exit that is external to a building. ... For other uses, see School (disambiguation). ...


Figure rolled glass

The elaborate patterns found on figure rolled glass are produced by in a similar fashion to the rolled plate glass process except that the plate is cast between two moving rollers. The pattern is impressed upon the sheet by a printing roller which is brought down upon the glass as it leaves the main rolls while still soft. This glass shows a pattern in high relief. The glass is then annealed in a lehr.


The glass used for this purpose is typically whiter in colour than the clear glasses used for other applications.


This glass can be laminated or toughened depending on the depth of the pattern to produce a safety glass.


Laminated glass

Automobile windshield displaying "spider web" cracking typical of laminated safety glass.
Enlarge
Automobile windshield displaying "spider web" cracking typical of laminated safety glass.

Laminated glass is a type of safety glass that holds together when shattered. In the event of breakage, it is held in place by an interlayer, typically of PVB, between its two or more layers of glass. The interlayer keeps the layers of glass bonded even when broken, and its high strength prevents the glass from breaking up into large sharp pieces. This produces a characteristic "spider web" cracking pattern when the impact is not enough to completely pierce the glass. ImageMetadata File history File links Download high resolution version (1349x655, 244 KB) Summary Windshield with spiderweb cracking. ... ImageMetadata File history File links Download high resolution version (1349x655, 244 KB) Summary Windshield with spiderweb cracking. ... Polyvinyl butyral (or PVB) is a resin usually used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. ...


Laminated glass is normally used when there is a possibility of human impact or where the glass could fall if shattered. Shopfront glazing and windshields are typically laminated glasses. The PVB interlayer also gives the glass a much higher sound insulation rating, due to the damping effect, and also blocks 99% of transmitted UV light. Using toughened glass on windshields would be a problem when a small stone hits the windshield at speed, if it were toughened and the stone hit with enough force the whole windshield would shatter into the small squares making visibility difficult and it would also be likely that the wind would blow the small squares into the driver and passengers. The windshield or windscreen of an aircraft, automobile, or motorcycle, is the front window. ...


Laminated glass was invented in 1903 by the French chemist Edouard Benedictus, inspired by a laboratory accident. A glass flask had become coated with the plastic cellulose nitrate and when dropped shattered but did not break into pieces. Benedictus fabricated a glass-plastic composite to reduce injuries in car accidents. However, it was not immediately adopted by automobile manufacturers, and the first widespread use of laminated glass was in the eyepieces of gas masks during World War I. 1903 (MCMIII) was a common year starting on Thursday (see link for calendar). ... Nitrocellulose (Cellulose nitrate, guncotton) is a highly flammable compound formed by nitrating cellulose (e. ... Composite materials (or composites for short) are engineered materials made from two or more constituent materials that remain separate and distinct on a macroscopic level while forming a single component. ... The result of excessive speed, this cement truck rolls over into the front garden of a house. ... This article or section does not cite its references or sources. ... Belgian 1930s era L.702 model civilian mask A gas mask, is a mask worn on the face to protect the body from airborne pollutants and toxic materials. ... Combatants Allies: Serbia, Russia, France, Romania, Belgium, British Empire, United States, Italy, and others Central Powers: Germany, Austria-Hungary, Bulgaria, Ottoman Empire Casualties Military dead: 5 million Civilian deaths: 3 million Total of dead: 8 million Military dead: 4 million Civilian deaths: 3 million Total dead: 7 million The First...


Today, laminated glass is produced by bonding two or more layers of ordinary annealed glass together with a plastic interlayer, usually polyvinyl butyral (PVB). The PVB is sandwiched by the glass which is passed through rollers to expel any air pockets and form the initial bond then heated to around 70 °C in a pressurized oil bath. The tint at the top of some car windshields is in the PVB. Polyvinyl butyral (or PVB) is a resin usually used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. ...


A typical laminated makeup would be 3 mm glass / 0.38 mm interlayer / 3 mm glass. This gives a final product that would be referred to as 6.38 laminated glass.


Multiple laminates and thicker glass increases the strength. Bulletproof glass is often made of several float glass, toughened glass and Perspex panels, and can be as thick as 100 mm. A similar glass is often used in airliners on the front windows, often three sheets of 6 mm toughened glass with thick PVB between them. Bulletproof glass is glass that is capable of stopping all manner of bullets fired at it. ...


Toughened glass or Tempered Glass

A vandalized phone booth with toughened glass
A vandalized phone booth with toughened glass

Toughened glass or tempered glass is a type of safety glass that has increased strength and will usually shatter in small, square pieces when broken. It is used when strength, thermal resistance and safety are important considerations. Download high resolution version (1536x2048, 1123 KB)Photo of phone box with smashed tempered glass in Holloway. ... Download high resolution version (1536x2048, 1123 KB)Photo of phone box with smashed tempered glass in Holloway. ... A caricature of Gustave Courbet taking down a Morris column, published by Le Père Duchêne illustré magazine Vandalism is the conspicuous defacement or destruction of a structure or symbol against the will of the owner/governing body. ... For the 2002 movie, see Phone Booth (movie). ...


At home you are likely to find toughened glass in shower and sliding glass patio doors. In commercial structures it is used in unframed assemblies such as frameless doors, structurally loaded applications and any glass where these is a danger of human impact.


Using toughened glass can pose a security risk in some situations due to the tendency the glass has to shatter utterly upon hard impact.


Toughened glass is typically four to six times the strength of annealed glass. However, this strength comes with a penalty. Due to the balanced stresses in the glass, damage to the glass will eventually result in the glass shattering into thumbnail sized pieces. Although toughened glass is most susceptible to breakage via edge damage, breakage can also occur from impacts in the centre of the glass pane.


Shattering may not happen when the damage originally occurs and can be triggered by a minor stress like heat or small impact that would not normally affect the toughened glass. If any toughened glass shows any damage it must be replaced.


Toughened glass must be cut to size or pressed to shape before toughening and cannot be re-worked once toughened. Polishing the edges or drilling holes in the glass is carried out before the toughening process starts. Also, ironically, the toughened glass surface is not as hard as annealed glass and is slightly more susceptible to scratching.


Toughened glass is made from annealed glass via a thermal tempering process. The glass is placed onto a roller table, taking it through a furnace which heats it to above its annealing point of 600 °C. The glass is then rapidly cooled with forced draughts of air. This rapidly cools the glass surface below its annealing point, causing it to harden and contract, while the inner portion of the glass remains free to flow for a short time. The final contraction of the inner layer induces compressive stresses in the surface of the glass balanced by tensile stresses in the body of the glass. This compressive stress on the surface of the glass is typically as high as 50 MPa. Annealing, in glassblowing and lampworking, is heating a piece of glass until its temperature reaches a stress-relief point, that is, a temperature at which the glass is still too hard to deform, but is soft enough for internal stresses to ease. ... Tensile stress (or tension) is the stress state leading to expansion; that is, the length of a material tends to increase in the tensile direction. ...


It is this compressive stress that gives the toughened glass an increased strength. This is because any surface flaws tend to be pressed closed by the retained compressive forces, while the core layer remains relatively free of the defects which could cause a crack to begin. Compression in material science, physics or structural engineering, is the stress state of materials where the volume tends to decrease (compaction). ... In physics, a force is anything that causes a free body with mass to accelerate. ...


The pattern of cooling during the process can be revealed by observing the glass with polarized light, which shows the strain pattern in the glass. This article treats polarization in electrodynamics. ...


Though the underlying mechanism was not known at the time, the effects of "tempering" glass have been known for centuries. In the 1640s, Prince Rupert of Bavaria (16191682), who was grandson of James I of England, and nephew of Charles I, brought the discovery of what are now known as "Prince Rupert's Drops" to the attention of the King. These are remarkable teardrop shaped bits of glass which are produced by allowing a molten drop of glass to fall into a bucket of water, thereby rapidly cooling it. These were often used by the King as a practical joke. Events and Trends The personal union of the crowns of Spain and Portugal ends due to a revolution in the latter (1640). ... Rupert, Count Palatine of the Rhine, Duke of Bavaria (German: Ruprecht Pfalzgraf bei Rhein, Herzog von Bayern), commonly called Prince Rupert of the Rhine, (17 December 1619 – 19 November 1682), soldier and inventor, was a younger son of Frederick V, Elector Palatine and Elizabeth Stuart, and the nephew of King... Events May 13 - Dutch statesman Johan van Oldenbarnevelt is executed in The Hague after having been accused of treason. ... Events March 11 – Chelsea hospital for soldiers is founded in England May 6 - Louis XIV of France moves his court to Versailles. ... James VI of Scotland/James I of England (Charles James Stuart) (June 19, 1566 – March 27, 1625) was King of England, King of Scotland and was the first to style himself King of Great Britain. ... Charles I (19 November 1600 – 30 January 1649) was King of England, Scotland, and Ireland from 27 March 1625 until his execution in 1649. ... Prince Ruperts Drops (or Ruperts Balls) are a glass curiosity created by dripping hot molten glass into cold water. ...


Chemically strengthened glass

Chemically strengthened glass is a type of glass that has increased strength. When broken it still shatters in long pointed splinters similar to float (annealed) glass. For this reason, it is not considered a safety glass and must be laminated if a safety glass is required.


Chemically strengthened glass is typically six to eight times the strength of annealed glass.


The glass is chemically strengthened by submersing the glass in a bath containing a potassium salt (typically potassium nitrate) at 450 °C. This causes sodium ions in the glass surface to be replaced by potassium ions from the bath solution.


These potassium ions are larger than the sodium ions and therefore wedge into the gaps left by the smaller sodium ions when they migrate to the potassium nitrate solution. This replacement of ions causes the surface of the glass to be in a state of compression and the core in compensating tension. The surface compression of chemically strengthened glass may reach up to 690 MPa.


There also exists a more advanced two-stage process for making chemically strengthened glass, in which the glass article is first immersed in a sodium nitrate bath at 450 °C, which enriches the surface with sodium ions. This leaves more sodium ions on the glass for the immersion in potassium nitrate to replace with potassium ions. In this way, the use of a sodium nitrate bath increases the potential for surface compression in the finished article.


Chemical strengthening results in a strengthening similar to toughened glass, however the process does not use extreme variations of temperature and therefore chemically strengthened glass has little or no bow or warp, optical distortion or strain pattern. This differs from toughened glass, in which slender pieces can often be significantly bowed.


Also unlike toughened glass, chemically strengthened glass may be cut after strengthening, but loses its added strength within the region of approximately 20 mm of the cut. Similarly, when the surface of chemically strengthened glass is deeply scratched, this area loses its additional strength.


Chemically strengthened glass was used on some fighter aircraft canopies. An A-10 Thunderbolt II, F-86 Sabre, P-38 Lightning and P-51 Mustang fly in formation during an air show at Langley Air Force Base, Virginia. ...


Low-emissivity glass

To make Low-E glass, certain properties such as the iron content may be controlled. Also, some types of glass have natural Low-e properties, such as borosilicate or "pyrex" (tm). Specially designed coatings, often based on metallic oxides, are applied to one or more surfaces of insulated glass. These coatings reflect radiant infrared energy, thus tending to keep radiant heat on the same side of the glass from which it originated. This often results in more efficient windows because: radiant heat originating from indoors is reflected back inside, thus keeping heat inside in the winter, and infrared radiation from the sun is reflected away, keeping it cooler inside in the summer. Window Technologies: Low-E Coatings Low-emittance (Low-E) coating are microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface primarily to reduce the U-factor by suppressing radiative heat flow. ... Hello Please take a look at my one of a kind custom pyrex glass dildos made in upstate Ny all hand sculpted not machined. ... Pyrex is a brand name of borosilicate glass introduced by Corning Glass Works in 1924. ... Insulated glazing is a piece of glazing consisting of two or more layers of glazing separated by a spacer along the edge and sealed to create a dead air space between the layers. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ...


Self-cleaning glass

A recent innovation is so-called self-cleaning glass, aimed at building, automotive and other technical applications. A 50 nanometre coating of titanium dioxide on the outer surface of glass introduces two mechanisms which lead to the self-cleaning property. The first is a photo-catalytic effect, in which ultra-violet rays catalyse the breakdown of organic compounds on the window surface; the second is a hydrophilic effect in which water is attracted to the surface of the glass, forming a thin sheet which washes away the broken-down organic compounds. Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurring oxide of titanium, chemical formula TiO2. ... Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... The adjective hydrophilic describes something that likes water (from Greek hydros = water; philos = friend). ...


Insulated glazing

Main article: insulated glazing. Insulated glazing is a piece of glazing consisting of two or more layers of glazing separated by a spacer along the edge and sealed to create a dead air space or a vacuum between the layers. ...


Insulated glazing, or double glazing is a piece of glazing consisting of two or more layers of glazing separated by a spacer along the edge and sealed to create a dead air space between the layers. This type of glazing has functions of thermal insulation and noise mitigation. Glazing, in architecture, is a transparent part of a wall, usually made of glass or plastic (acrylic and polycarbonate). ... Dead Air Space is a blog kept by members of the British band Radiohead on their aptly titled website Radiohead. ... Roadway noise is the most pervasive form of environmental noise Noise mitigation is a set of strategies to reduce unwanted environmental sound. ...


Evacuated glazing

Another recent innovation for insulated glazing is evacuated glass, which as yet is produced commercially only in Japan. The extreme thinness of evacuated glazing offers many new architectural possibilities, particularly in building conservation and historicist architecture, where evacuated glazing can replace traditional (much less energy-efficient) single glazing.


An evacuated glazing unit is made by sealing the edges of two glass sheets, typically by using a solder glass, and evacuating the space inside with a vacuum pump. The evacuated space between the two sheets can be very shallow and yet be a good insulator, yielding insulative window glass with nominal thicknesses as low as 6 mm overall. The reasons for this low thickness are deceptively complex, but the potential insulation is good essentially because there can be no convection or gaseous conduction in a vacuum.


Unfortunately, evacuated glazing does have some disadvantages; its manufacture is complicated and difficult. For example, a necessary stage in the manufacture of evacuated glazing is outgassing; that is, heating it to liberate any gasses adsorbed on the inner surfaces, which could otherwise later escape and destroy the vacuum. This heating process currently means that evacuated glazing cannot be toughened or heat-strengthened. If an evacuated safety glass is required, the glass must be laminated. The high temperatures necessary for outgassing also tend to destroy the highly effective "soft" low-emissivity coatings that are often applied to one or both of the internal surfaces (i.e. the ones facing the air gap) of other forms of modern insulative glazing, in order to prevent loss of heat through infrared radiation. Slightly less effective "hard" coatings are still suitable for evacuated glazing, however. Window Technologies: Low-E Coatings Low-emittance (Low-E) coating are microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface primarily to reduce the U-factor by suppressing radiative heat flow. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ...


Furthermore, because of the atmospheric pressure present on the outside of an evacuated glazing unit, its two glass sheets must somehow be held apart in order to prevent them flexing together and touching each other, which would defeat the object of evacuating the unit. The task of holding the panes apart is performed by a grid of spacers, which typically consist of small stainless steel discs that are placed around 20 mm apart. The spacers are small enough that they are visible only at very close distances, typically up to 1 m. However, the fact that the spacers will conduct some heat often leads in cold weather to the formation of temporary, grid-shaped patterns on the surface of an evacuated window, consisting either of small circles of interior condensation centred around the spacers, where the glass is slightly colder than average, or, when there is dew outside, small circles on the exterior face of the glass, in which the dew is absent because the spacers make the glass near them slightly warmer.


The conduction of heat between the panes, caused by the spacers, tends to limit evacuated glazing’s overall insulative effectiveness. Nevertheless, evacuated glazing is still as insulative as much thicker conventional double glazing and tends to be stronger, since the two constituent glass sheets are pressed together by the atmosphere, and hence react practically as one thick sheet to bending forces. Evacuated glazing also offers very good sound insulation in comparison with other popular types of window glazing.


References

  • Noel C. Stokes; The Glass and Glazing Handbook; Standards Australia; SAA HB125-1998

See also


 
 

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