Glass
thumb|380px|A glass building facade
Glass is a non-crystalline, often transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of the molten form, some glasses such as volcanic glass are naturally occurring.  The most familiar, and historically the oldest, types of manufactured glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand.  Soda-lime glass, containing around 70% silica, account for around 90% of manufactured glass. The term glass, in popular usage, is often used to refer only to this type of material, although silica-free glasses often have desirable properties for applications in modern communications technology. Some objects, such as drinking glasses and eyeglasses, are so commonly made of silicate-based glass that they are simply called by the name of the material.

Although brittle, silicate glass is extremely durable, and many examples of glass fragments exist from early glass-making cultures. Archaeological evidence suggests glass-making dates back to at least 3,600 BCE in Mesopotamia, Egypt, or Syria. The earliest known glass objects were beads, perhaps created accidentally during metal-working or the production of faience.  Due to its ease of formability into any shape, glass has been traditionally used for vessels: bowls, vases, bottles, jars and drinking glasses. In its most solid forms, it has also been used for paperweights, marbles. Glass can be coloured by adding metal salts or painted and printed with vitreous enamels, leading to its use in stained glass windows and other glass art objects.

The refractive, reflective and transmission properties of glass make glass suitable for manufacturing optical lenses, prisms, and optoelectronics materials. Extruded glass fibres have application as optical fibres in communications networks, thermal insulating material when matted as glass wool so as to trap air, or in glass-fibre reinforced plastic (fibreglass).

Glass structure (microscopic)
thumb|left|The amorphous structure of glassy silica (SiO2) in two dimensions. No long-range order is present, although there is local ordering with respect to the tetrahedral arrangement of oxygen (O) atoms around the silicon (Si) atoms.

The standard definition of a glass (or vitreous solid) is a solid formed by rapid melt quenching.ASTM definition of glass from 1945  However, the term "glass" is often defined in a broader sense, to describe any non-crystalline (amorphous) solid that exhibits a glass transition when heated towards the liquid state.

Glass is an amorphous solid. Although the atomic-scale structure of glass shares characteristics of the structure of a supercooled liquid, glass exhibits all the mechanical properties of a solid."Philip Gibbs" Glass Worldwide, (May/June 2007), pp. 14–18 As in other amorphous solids, the atomic structure of a glass lacks the long-range periodicity observed in crystalline solids. Due to chemical bonding constraints, glasses do possess a high degree of short-range order with respect to local atomic polyhedra. The notion that glass flows to an appreciable extent over extended periods of time is not supported by empirical research or theoretical analysis (see viscosity in solids). Laboratory measurements of room temperature glass flow do show a motion consistent with a material viscosity on the order of 1017–1018 Pa s.

Formation from a supercooled liquid

For melt quenching, if the cooling is sufficiently rapid (relative to the characteristic crystallization time) then crystallization is prevented and instead the disordered atomic configuration of the supercooled liquid is frozen into the solid state at Tg. The tendency for a material to form a glass while quenched is called glass-forming ability. This ability can be predicted by the rigidity theory. Generally, a glass exists in a structurally metastable state with respect to its crystalline form, although in certain circumstances, for example in atactic polymers, there is no crystalline analogue of the amorphous phase.

Glass is sometimes considered to be a liquid due to its lack of a first-order phase transition
where certain thermodynamic variables such as volume, entropy and enthalpy are discontinuous through the glass transition range. The glass transition may be described as analogous to a second-order phase transition where the intensive thermodynamic variables such as the thermal expansivity and heat capacity are discontinuous. Nonetheless, the equilibrium theory of phase transformations does not entirely hold for glass, and hence the glass transition cannot be classed as one of the classical equilibrium phase transformations in solids.

Occurrence in Nature

Glass can form naturally from volcanic magma. Obsidian is a common volcanic glass with high silica (SiO2) content formed when felsic lava extruded from a volcano cools rapidly. Impactite is a form of glass formed by the impact of a meteorite, where Moldavite (found in central and eastern Europe), and Libyan desert glass (found in areas in the eastern Sahara, the deserts of eastern Libya and western Egypt) are notable examples. Vitrification of quartz can also occur when lightning strikes sand, forming hollow, branching rootlike structures called fulgurites. Trinitite is a glassy residue formed from the desert floor sand at the Trinity nuclear bomb test site. Edeowie glass, found in South Australia, is proposed to originate from Pleistocene grassland fires, lightning strikes, or hypervelocity impact by one or several asteroids or comets. 

History

thumb|right|upright|Roman cage cup from the 4th century CE

Naturally occurring obsidian glass was used by Stone Age societies as it fractures along very sharp edges, making it ideal for cutting tools and weapons. Archaeological evidence suggests that the first true synthetic glass was made in Lebanon and the coastal north Syria, Mesopotamia or ancient Egypt. The earliest known glass objects, of the mid third millennium BCE, were beads, perhaps initially created as accidental by-products of metal-working (slags) or during the production of faience, a pre-glass vitreous material made by a process similar to glazing.

During the Late Bronze Age there was a rapid growth in glassmaking technology in Egypt and Western Asian. Archaeological finds from this period include coloured glass ingots, vessels, and beads. Much early glass production relied on grinding techniques borrowed from stone working meaning that glass was ground and carved in a cold state.Wilde, H. "Technologische Innovationen im 2. Jahrtausend v. Chr. Zur Verwendung und Verbreitung neuer Werkstoffe im ostmediterranen Raum". GOF IV, Bd 44, Wiesbaden 2003, 25–26. However, glass remained a luxury material, and the disasters that overtook Late Bronze Age civilizations seem to have brought glass-making to a halt. Indigenous development of glass technology in South Asia may have begun in 1730 BCE. In ancient China, though, glassmaking seems to have a late start, compared to ceramics and metal work.  The term glass developed in the late Roman Empire. It was in the Roman glassmaking centre at Trier, now in modern Germany, that the late-Latin term glesum originated, probably from a Germanic word for a transparent, lustrous substance. Glass objects have been recovered across the Roman Empire in domestic, funerary, and industrial contexts. Examples of Roman glass have been found outside of the former Roman Empire in China, the Baltics, the Middle East and India.

thumb|right|Windows in the choir of the Basilica of Saint Denis, one of the earliest uses of extensive areas of glass (early 13th-century architecture with restored glass of the 19th century)
Glass was used extensively during the Middle Ages. Anglo-Saxon glass has been found across England during archaeological excavations of both settlement and cemetery sites. Glass in the Anglo-Saxon period was used in the manufacture of a range of objects including vessels, windows, beads, and was also used in jewelry. From the 10th-century onwards, glass was employed in stained glass windows of churches and cathedrals, with famous examples at Chartres Cathedral and the Basilica of Saint Denis. By the 14th-century, architects were designing buildings with walls of stained glass such as Sainte-Chapelle, Paris, (1203–1248)Rene Hughe, Byzantine and Medieval Art, Paul Hamlyn, (1963) and the East end of Gloucester Cathedral.John Harvey, English Cathedrals, Batsford, (1961) Stained glass had a major revival with Gothic Revival architecture in the 19th century. With the Renaissance, and a change in architectural style, the use of large stained glass windows became less prevalent. 
The use of domestic stained glass increased until most substantial houses had glass windows. These were initially small panes leaded together, but with the changes in technology, glass could be manufactured relatively cheaply in increasingly larger sheets, leading to larger window panes.

In the 1920s a mould-etch process was developed, in which art was etched directly into the mould, so that each cast piece emerged from the mould with the image already on the surface of the glass. This reduced manufacturing costs and, combined with a wider use of coloured glass, led to cheap glassware in the 1930s, which later became known as Depression glass. Throughout the 20th century, new types of glass such as laminated glass, reinforced glass and glass bricks increased the use of glass as a building material and resulted in new applications of glass. Multi-story buildings are frequently constructed with curtain walls made almost entirely of glass. Similarly, laminated glass has been widely applied to vehicles for windscreens. Optical glass for spectacles has been used since the Middle Ages. The production of lenses has become increasingly proficient, aiding astronomers as well as having other application in medicine and science. Glass is also employed as the aperture cover in many solar energy collectors.

In the 21st century, glass manufacturers have developed different brands of chemically strengthened glass for widespread application in touchscreens for smartphones, tablet computers, and many other types of information appliances. These include Gorilla glass, developed and manufactured by Corning, AGC Inc.'s Dragontrail and Schott AG's Xensation.

Physical properties
Optical properties
Glass is in widespread use largely due to the production of glass compositions that are transparent to visible light. In contrast, polycrystalline materials do not generally transmit visible light. The individual crystallites may be transparent, but their facets (grain boundaries) reflect or scatter light resulting in diffuse reflection. Glass does not contain the internal subdivisions associated with grain boundaries in polycrystals and hence does not scatter light in the same manner as a polycrystalline material. The surface of a glass is often smooth since during glass formation the molecules of the supercooled liquid are not forced to dispose in rigid crystal geometries and can follow surface tension, which imposes a microscopically smooth surface. These properties, which give glass its clearness, can be retained even if glass is partially light-absorbing, i.e., coloured. Semi-opacity due to crystallization may be induced in many glasses by maintaining them for a long period at a temperature just insufficient to cause fusion. In this way, the crystalline, devitrified material, known as Réaumur's glass porcelain is produced.

Glass has the ability to refract, reflect, and transmit light following geometrical optics, without scattering it (due to the absence of grain boundaries). As such glass materials are widely used in the manufacture of lenses, mirrors, and windows. Common glass has a refraction index around 1.5, which may be modified by high-density (refractive index increases) or low-density (refractive index decreases) additives.

Other properties

In the manufacturing process, glasses can be poured, formed, extruded and molded into forms ranging from flat sheets to highly intricate shapes. The finished product is brittle and will fracture, unless laminated or specially treated, but is extremely durable under most conditions. It erodes very slowly and can mostly withstand the action of water. It is mostly resistant to chemical attack, does not react with foods, and is an ideal material for the manufacture of containers for foodstuffs and most chemicals. Glass is also a fairly inert substance.

Although glass is generally more corrosion-resistant compared to other common materials, it will still corrode or dissolve under some conditions. The materials that make up a particular glass composition have an effect on how quickly the glass corrodes. A glass containing a high proportion of alkalis or alkali earths is less corrosion-resistant than other kinds of glasses. Glass flakes have applications as anti-corrosive coating.

Glass typically has a tensile strength of , however theoretically it can have a strength of  due to glass's strong chemical bonds. Several factors such as imperfections like scratches and bubbles and the glass's chemical composition impact the tensile strength of glass. Several processes such as toughening can increase the strength of glass.

Reputed glass flow
The observation that old windows are sometimes found to be thicker at the bottom than at the top is often offered as supporting evidence for the view that glass flows over a timescale of centuries, the assumption being that the glass has exhibited the liquid property of flowing from one shape to another. This assumption is incorrect, as once solidified, glass stops flowing. Instead, glass manufacturing processes in the past produced sheets of non-uniform thickness leading to observed sagging and ripples in old windows.

Types
Silicate glass
thumb|right|Quartz sand (silica) is the main raw material in commercial glass production
Silicon dioxide (SiO2) is a common fundamental constituent of glass. Fused quartz, also called fused-silica glass, is a glass made from chemically-pure silica. It has very low thermal expansion and excellent resistance to thermal shock, being able to survive immersion in water while red hot, resists high temperatures (1000–1500 °C) and chemical weathering, and is very hard. Fused quartz is used for high-temperature applications such as furnace tubes, lighting tubes, melting crucibles, etc. However, its high melting temperature (1723 °C) and viscosity make it difficult to work with. Therefore, normally other substances are added to simplify glass processing. Sodium carbonate (Na2CO3, "soda") is a common additive and acts to lowers the glass-transition temperature. However, Sodium silicate is water-soluble, so lime (CaO, calcium oxide, generally obtained from limestone), some magnesium oxide (MgO) and aluminium oxide (Al2O3) are other common components added to improve chemical durability. Soda-lime glasses (Na2O) + lime (CaO) + magnesia (MgO) + alumina (Al2O3) account for about 90% of manufactured glass, containing about 70 to 74% silica by weight.B.H.W.S. de Jong, "Glass"; in "Ullmann's Encyclopedia of Industrial Chemistry"; 5th edition, vol. A12, VCH Publishers, Weinheim, Germany, 1989, , pp. 365–432. Soda-lime-silicate glass is transparent, easily formed, and most suitable for window glass and tableware. However, it has a high thermal expansion and poor resistance to heat. Container glass is a soda-lime glass that is a slight variation on flat glass, with higher alumina and calcium content, and less sodium and magnesium (which are more water-soluble), making it less susceptible to water erosion. Further ingredients may be added to change the properties of silicate glass.

Borosilicate glass
thumb|right|A Pyrex borosilicate glass measuring jug
Borosilicate glasses (e.g. Pyrex, Duran) have as main constituents silica and boron trioxide (B2O3) + soda (Na2O) + alumina (Al2O3). Borosilicate glasses have fairly low coefficients of thermal expansion (7740 Pyrex CTE is 3.25/°C as compared to about 9/°C for a typical soda-lime glass). They are, therefore, less subject to stress caused by thermal expansion and thus less vulnerable to cracking from thermal shock. They are commonly used for e.g. chemical reagent glassware, optical components, household cookware, and car head lamps.

Lead glass
thumb|right|Lead glass, a glass made by adding lead oxide to glass
The addition of lead(II) oxide into silicate glass lowers melting point, lowers viscosity of the melt, and increases refractive index. The high density of Lead glass (silica + lead oxide (PbO) + potassium oxide (K2O) + soda (Na2O) + zinc oxide (ZnO) + alumina) is more "brilliant" and causes noticeably more specular reflection and increased optical dispersion. results in a high electron density, and hence high refractive index, making the look of glassware more brilliant and causing noticeably more specular reflection and increased optical dispersion. As a result, it is often referred to as "crystal", although it is a glass and not a crystal.  It has a high elasticity, making glassware "ring" and is more workable in the factory, but cannot stand heating very well. This kind of glass is also more fragile than other glasses and is easier to cut. Lead oxide also facilitates solubility of other metal oxides and is used in colored glass. The viscosity decrease of lead glass melt is very significant (roughly 100 times in comparison with soda glass); this allows easier removal of bubbles and working at lower temperatures, hence its frequent use as an additive in vitreous enamels and glass solders. The high ionic radius of the Pb2+ ion renders it highly immobile and hinders the movement of other ions; lead glasses therefore have high electrical resistance, about two orders of magnitude higher than soda-lime glass (108.5 vs 106.5 Ω⋅cm, DC at 250 °C).

Aluminosilicate glass
Aluminosilicate glass (silica + alumina + lime + magnesia) + barium oxide (BaO) + boric oxide (B2O3). is extensively used for fiberglass, used for making glass-reinforced plastics (boats, fishing rods, etc.) and for halogen bulb glass. Aluminosilicate glasses are resistant to weathering and water erosion.

Other oxide additives
The addition of barium also increases the refractive index. Thorium oxide gives glass a high refractive index and low dispersion and was formerly used in producing high-quality lenses, but due to its radioactivity has been replaced by lanthanum oxide in modern eyeglasses. Iron can be incorporated into glass to absorb infrared radiation, for example in heat-absorbing filters for movie projectors, while cerium(IV) oxide can be used for glass that absorbs ultraviolet wavelengths. Fluorine lowers the dielectric constant of glass. Fluorine is highly electronegative and lowers the polarizability of the material. Fluoride silicate glasses are used in manufacture of integrated circuits as an insulator.

Glass-ceramics

right|thumb|A high-strength glass-ceramic cooktop with negligible thermal expansion.
Glass-ceramic materials share many properties with both non-crystalline glass and crystalline ceramics. They are formed as a glass, and then partially crystallized by heat treatment. For example, the microstructure of whiteware ceramics frequently contains both amorphous and crystalline phases. Crystalline grains are often embedded within a non-crystalline intergranular phase of grain boundaries. When applied to whiteware ceramics, vitreous means the material has an extremely low permeability to liquids, often but not always water, when determined by a specified test regime.

The term mainly refers to a mix of lithium and aluminosilicates that yields an array of materials with interesting thermomechanical properties. The most commercially important of these have the distinction of being impervious to thermal shock. Thus, glass-ceramics have become extremely useful for countertop cooking. The negative thermal expansion coefficient (CTE) of the crystalline ceramic phase can be balanced with the positive CTE of the glassy phase. At a certain point (~70% crystalline) the glass-ceramic has a net CTE near zero. This type of glass-ceramic exhibits excellent mechanical properties and can sustain repeated and quick temperature changes up to 1000 °C.

 Fibreglass 

Fibreglass (also called glass-reinforced-plastic) is a composite material made up of glass fibres (also called fiberglass or glass friller) embedded in a plastic resin. It is made by melting glass and stretching the glass into fibres. These fibres are woven together into a cloth and left to set in a plastic resin.

Fibreglass filaments are made through a pultrusion process in which the raw materials (sand, limestone, kaolin clay, fluorspar, colemanite, dolomite and other minerals)  are melted in a large furnace into a liquid which is extruded through very small orifices (5–25 micrometres in diameter if the glass is E-glass and 9 micrometers if the glass is S-glass).

Fibreglass has the properties of being lightweight and corrosion resistant. Fibreglass is also a good insulator, allowing it to be used to insulate buildings. Most fiberglasses are not alkali resistant. Fibreglass also has the property of becoming stronger as the glass ages.

Silica-free glass
thumb|right|A CD-RW (CD). Chalcogenide glass form the basis of rewritable CD and DVD solid-state memory technology.
Besides common silica-based glasses many other inorganic and organic materials may also form glasses, including metals, aluminates, phosphates, borates, chalcogenides, fluorides, germanates (glasses based on GeO2), tellurites (glasses based on TeO2), antimonates (glasses based on Sb2O3), arsenates (glasses based on As2O3), titanates (glasses based on TiO2), tantalates (glasses based on Ta2O5), nitrates, carbonates, plastics, acrylic, and many other substances. Some of these glasses (e.g. Germanium dioxide (GeO2, Germania), in many respects a structural analogue of silica, fluoride, aluminate, phosphate, borate, and chalcogenide glasses) have physico-chemical properties useful for their application in fibre-optic waveguides in communication networks and other specialized technological applications.

Silica-free glasses may often have poor glass forming tendencies. Novel techniques are used to increase cooling rate, or reduce crystal nucleation triggers. Examples of these techniques include aerodynamic levitation (cooling the melt whilst it floats on a gas stream), splat quenching (pressing the melt between two metal anvils) and roller quenching (pouring the melt through rollers).

Amorphous metals

thumb|Samples of amorphous metal, with millimeter scale
In the past, small batches of amorphous metals with high surface area configurations (ribbons, wires, films, etc.) have been produced through the implementation of extremely rapid rates of cooling. Amorphous metal wires have been produced by sputtering molten metal onto a spinning metal disk. More recently a number of alloys have been produced in layers with thickness exceeding 1 millimeter. These are known as bulk metallic glasses (BMG). Liquidmetal Technologies sell a number of zirconium-based BMGs. Batches of amorphous steel have also been produced that demonstrate mechanical properties far exceeding those found in conventional steel alloys.

In 2004, NIST researchers presented evidence that an isotropic non-crystalline metallic phase (dubbed "q-glass") could be grown from the melt. This phase is the first phase, or "primary phase", to form in the Al-Fe-Si system during rapid cooling. Experimental evidence indicates that this phase forms by a first-order transition. Transmission electron microscopy (TEM) images show that the q-glass nucleates from the melt as discrete particles, which grow spherically with a uniform growth rate in all directions. The diffraction pattern shows it to be an isotropic glassy phase. Yet there is a nucleation barrier, which implies an interfacial discontinuity (or internal surface) between the glass and the melt.

Polymers
Important polymer glasses include amorphous and glassy pharmaceutical compounds. These are useful because the solubility of the compound is greatly increased when it is amorphous compared to the same crystalline composition. Many emerging pharmaceuticals are practically insoluble in their crystalline forms. Many polymer thermoplastics familiar from everyday use are glasses. For many applications, like glass bottles or eyewear, polymer glasses (acrylic glass, polycarbonate or polyethylene terephthalate) are a lighter alternative to traditional glass.

Molecular liquids and molten salts
Molecular liquids, electrolytes, molten salts, and aqueous solutions are mixtures of different molecules or ions that do not form a covalent network but interact only through weak van der Waals forces or through transient hydrogen bonds. In a mixture of three or more ionic species of dissimilar size and shape, crystallization can be so difficult that the liquid can easily be supercooled into a glass. Examples include LiCl:RH2O (a solution of lithium chloride salt and water molecules) in the composition range 4<R<8. European Workshop on Glasses and Gels. sugar glass, or Ca0.4K0.6(NO3)1.4. Glass electrolytes in the form of Ba-doped Li-glass and Ba-doped Na-glass have been proposed as solutions to problems identified with organic liquid electrolytes used in modern lithium-ion battery cells.

Production

thumb|right|Robotized Float Glass Unloading
Following the glass batch preparation and mixing, the raw materials are transported to the furnace. Soda-lime glass for mass production is melted in gas fired units. Smaller scale furnaces for specialty glasses include electric melters, pot furnaces, and day tanks.
After melting, homogenization and refining (removal of bubbles), the glass is formed. Flat glass for windows and similar applications is formed by the float glass process, developed between 1953 and 1957 by Sir Alastair Pilkington and Kenneth Bickerstaff of the UK's Pilkington Brothers, who created a continuous ribbon of glass using a molten tin bath on which the molten glass flows unhindered under the influence of gravity. The top surface of the glass is subjected to nitrogen under pressure to obtain a polished finish.
Container glass for common bottles and jars is formed by blowing and pressing methods. This glass is often slightly modified chemically (with more alumina and calcium oxide) for greater water resistance.
thumb|right|Glass blowing

Once the desired form is obtained, glass is usually annealed for the removal of stresses and to increase the glass's hardness and durability. Surface treatments, coatings or lamination may follow to improve the chemical durability (glass container coatings, glass container internal treatment), strength (toughened glass, bulletproof glass, windshields), or optical properties (insulated glazing, anti-reflective coating).

New chemical glass compositions or new treatment techniques can be initially investigated in small-scale laboratory experiments. The raw materials for laboratory-scale glass melts are often different from those used in mass production because the cost factor has a low priority. In the laboratory mostly pure chemicals are used. Care must be taken that the raw materials have not reacted with moisture or other chemicals in the environment (such as alkali or alkaline earth metal oxides and hydroxides, or boron oxide), or that the impurities are quantified (loss on ignition). Evaporation losses during glass melting should be considered during the selection of the raw materials, e.g., sodium selenite may be preferred over easily evaporating selenium dioxide (SeO2). Also, more readily reacting raw materials may be preferred over relatively inert ones, such as aluminum hydroxide (Al(OH)3) over alumina (Al2O3). Usually, the melts are carried out in platinum crucibles to reduce contamination from the crucible material. Glass homogeneity is achieved by homogenizing the raw materials mixture (glass batch), by stirring the melt, and by crushing and re-melting the first melt. The obtained glass is usually annealed to prevent breakage during processing.

Colour

Colour in glass may be obtained by addition of electrically charged ions (or colour centres) that are homogeneously distributed, and by precipitation of finely dispersed particles (such as in photochromic glasses). 
While ordinary soda-lime glass appears colourless in thin section, iron(II) oxide (FeO) impurities produce a green tint in thick sections. Manganese dioxide (MnO2), which gives glass a purple colour, may be added to remove the green tint given by FeO. FeO and chromium(III) oxide (Cr2O3) additives are used in the production of green bottles. Iron (III) oxide, on the other-hand, produces yellow or yellow-brown glass. Low concentrations (0.025 to 0.1%) of cobalt oxide (CoO) produces rich, deep blue cobalt glass. Chromium is a very powerful colourising agent, yielding dark green.Chemical Fact Sheet - Chromium  www.speclab.com.
Sulphur combined with carbon and iron salts produces amber glass ranging from yellowish to almost black.David M Issitt. Substances Used in the Making of Coloured Glass 1st.glassman.com. A glass melt can also acquire an amber colour from a reducing combustion atmosphere. Cadmium sulfide produces imperial red, and combined with selenium can produce shades of yellow, orange, and red. The additive Copper(II) oxide (CuO) produces a turquoise colour in glass, in contrast to Copper(I) oxide (Cu2O) which gives a dull brown-red colour.

Glass art

From the 19th century, there was a revival in many ancient glass-making techniques including cameo glass, achieved for the first time since the Roman Empire and initially mostly used for pieces in a neo-classical style. The Art Nouveau movement made great use of glass, with René Lalique, Émile Gallé, and Daum of Nancy important names in the first French wave of the movement, producing coloured vases and similar pieces, often in cameo glass, and also using luster techniques. Louis Comfort Tiffany in America specialized in stained glass, both secular and religious, both in panels and his famous lamps. The early 20th-century saw the large-scale factory production of glass art by firms such as Waterford and Lalique. From about 1960 onwards, there have been an increasing number of small studios hand-producing glass artworks, and glass artists began to class themselves as in effect sculptors working in glass, and their works as part fine arts.

Several of the most common techniques for producing glass art include: blowing, kiln-casting, fusing, slumping, pâté-de-verre, flame-working, hot-sculpting and cold-working. Cold work includes traditional stained glass work as well as other methods of shaping glass at room temperature. Glass can also be cut with a diamond saw, or copper wheels embedded with abrasives, and polished to give gleaming facets; the technique used in creating Waterford crystal. Art is sometimes etched into glass via the use of acid, caustic, or abrasive substances. Traditionally this was done after the glass was blown or cast.

Objects made out of glass include not only traditional objects such as vessels (bowls, vases, bottles, and other containers), paperweights, marbles, beads, but also an endless range of sculpture and installation art as well. Coloured glass is often used, though sometimes the glass is painted, innumerable examples exist of the use of stained glass.

See also

 Caneworking
 Colloid
 Fabrication and testing of optical components
 Fire glass
 Glassy carbon
 Gorilla Glass
 Kimberley points
 Low-iron glass
 Murrine
 Optical lens design
 Prince Rupert's drop
 Superglass
 Tektite

References

External links

 

 The Story of Glass Making in Canada from The Canadian Museum of Civilization.
  "How Your Glass Ware Is Made"  by George W. Waltz, February 1951, Popular Science.
 All About Glass from the Corning Museum of Glass: a collection of articles, multimedia, and virtual books all about glass, including the Glass Dictionary.
 National Glass Association the largest trade association representing the flat (architectural), auto glass, and window & door industries

 
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