Glass is a non-crystalline, amorphous solid that is often transparent and has widespread practical, technological, and decorative uses in, for example, window panes, tableware, and optoelectronics. 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. The term glass, in popular usage, is often used to refer only to this type of material, which is familiar from use as window glass and in glass bottles. Of the many silica-based glasses that exist, ordinary glazing and container glass is formed from a specific type called soda-lime glass, composed of approximately 75% silicon dioxide (SiO2), sodium oxide (Na2O) from sodium carbonate (Na2CO3), calcium oxide (CaO), also called lime, and several minor additives.
Many applications of silicate glasses derive from their optical transparency, giving rise to their primary use as window panes. Glass will transmit, reflect and refract light; these qualities can be enhanced by cutting and polishing to make optical lenses, prisms, fine glassware, and optical fibers for high speed data transmission by light. Glass can be coloured by adding metallic salts, and can also be painted and printed with vitreous enamels. These qualities have led to the extensive use of glass in the manufacture of art objects and in particular, stained glass windows. Although brittle, silicate glass is extremely durable, and many examples of glass fragments exist from early glass-making cultures. Because glass can be formed or moulded into any shape, it 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, and beads. When extruded as glass fiber and matted as glass wool in a way to trap air, it becomes a thermal insulating material, and when these glass fibers are embedded into an organic polymer plastic, they are a key structural reinforcement part of the composite material fiberglass. Some objects historically were so commonly made of silicate glass that they are simply called by the name of the material, such as drinking glasses and eyeglasses.
Scientifically, the term "glass" is often defined in a broader sense, encompassing every solid that possesses a non-crystalline (that is, amorphous) structure at the atomic scale and that exhibits a glass transition when heated towards the liquid state. Porcelains and many polymer thermoplastics familiar from everyday use are glasses. These sorts of glasses can be made of quite different kinds of materials than silica: metallic alloys, ionic melts, aqueous solutions, molecular liquids, and polymers. For many applications, like glass bottles or eyewear, polymer glasses (acrylic glass, polycarbonate or polyethylene terephthalate) are a lighter alternative than traditional glass.
Silicon dioxide (SiO2) is a common fundamental constituent of glass. In nature, vitrification of quartz occurs when lightning strikes sand, forming hollow, branching rootlike structures called fulgurites.
Fused quartz is a glass made from chemically-pure silica. It has excellent resistance to thermal shock, being able to survive immersion in water while red hot. However, its high melting temperature (1723 °C) and viscosity make it difficult to work with. Normally, other substances are added to simplify processing. One is sodium carbonate (Na2CO3, "soda"), which lowers the glass-transition temperature. The soda makes the glass water-soluble, which is usually undesirable, so lime (CaO, calcium oxide, generally obtained from limestone), some magnesium oxide (MgO) and aluminium oxide (Al2O3) are added to provide for a better chemical durability. The resulting glass contains about 70 to 74% silica by weight and is called a soda-lime glass. Soda-lime glasses account for about 90% of manufactured glass.
Most common glass contains other ingredients to change its properties. Lead glass or flint glass is more "brilliant" because the increased refractive index causes noticeably more specular reflection and increased optical dispersion. Adding 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.
The following is a list of the more common types of silicate glasses and their ingredients, properties, and applications:
Another common glass ingredient is crushed alkali glass or 'cullet' ready for recycled glass. The recycled glass saves on raw materials and energy. Impurities in the cullet can lead to product and equipment failure. Fining agents such as sodium sulfate, sodium chloride, or antimony oxide may be added to reduce the number of air bubbles in the glass mixture. Glass batch calculation is the method by which the correct raw material mixture is determined to achieve the desired glass composition.
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., colored.
Glass has the ability to refract, reflect, and transmit light following geometrical optics, without scattering it (due to the absence of grain boundaries). It is used in the manufacture of lenses and windows. Common glass has a refraction index around 1.5. This may be modified by adding low-density materials such as boron, which lowers the index of refraction (see crown glass), or increased (to as much as 1.8) with high-density materials such as (classically) lead oxide (see flint glass and lead glass), or in modern uses, less toxic oxides of zirconium, titanium, or barium. These high-index glasses (inaccurately known as "crystal" when used in glass vessels) cause more chromatic dispersion of light, and are prized for their diamond-like optical properties.
According to Fresnel equations, the reflectivity of a sheet of glass is about 4% per surface (at normal incidence in air), and the transmissivity of one element (two surfaces) is about 90%. Glass with high germanium oxide content also finds application in optoelectronics—e.g., for light-transmitting optical fibers.
In the process of manufacture, silicate glass 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 corrosion-resistant and more corrosion resistant than other materials, it still can be corroded. 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 typically has a tensile strength of 7 megapascals (1,000 psi), however theoretically it can have a strength of 17 gigapascals (2,500,000 psi) 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.
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. Further glass forming techniques are summarized in the table Glass forming techniques.
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).
Color in glass may be obtained by addition of electrically charged ions (or color centers) that are homogeneously distributed, and by precipitation of finely dispersed particles (such as in photochromic glasses). Ordinary soda-lime glass appears colorless to the naked eye when it is thin, although iron(II) oxide (FeO) impurities of up to 0.1 wt% produce a green tint, which can be viewed in thick pieces or with the aid of scientific instruments. Further FeO and chromium(III) oxide (Cr2O3) additions may be used for the production of green bottles. Sulfur, together with carbon and iron salts, is used to form iron polysulfides and produce amber glass ranging from yellowish to almost black. A glass melt can also acquire an amber color from a reducing combustion atmosphere. Manganese dioxide can be added in small amounts to remove the green tint given by iron(II) oxide. Art glass and studio glass pieces are colored using closely guarded recipes that involve specific combinations of metal oxides, melting temperatures and "cook" times. Most colored glass used in the art market is manufactured in volume by vendors who serve this market, although there are some glassmakers with the ability to make their own color from raw materials.
Naturally occurring glass, especially the volcanic glass obsidian, was used by many Stone Age societies across the globe for the production of sharp cutting tools and, due to its limited source areas, was extensively traded. Archaeological evidence suggests that the first true glass was made in 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.
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 center 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.
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) and the East end of Gloucester Cathedral. 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. This led to larger window panes, and, in the 20th-century, to much larger windows in ordinary domestic and commercial buildings.
In 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.
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 producing colored 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, 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.
In the 21st century, scientists observe the properties of ancient stained glass windows, in which suspended nanoparticles prevent UV light from causing chemical reactions that change image colors, are developing photographic techniques that use similar stained glass to capture true color images of Mars for the 2019 ESA Mars Rover mission.
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 SeO2. Also, more readily reacting raw materials may be preferred over relatively inert ones, such as Al(OH)3 over 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.
To make glass from materials with 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).
Fiberglass (also called glass-reinforced-plastic) is a composite material made up of glass fibers (also called fiberglass or glass friller) embedded in a plastic resin. It is made by melting glass and stretching the glass into fibers. These fibers are woven together into a cloth and left to set in a plastic resin.
Fiberglass 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).
Fiberglass has the properties of being lightweight and corrosion resistant. Fiberglass is also a good insulator, allowing it to be used to insulate buildings. Most fiberglasses are not alkali resistant. Fiberglass also has the property of becoming stronger as the glass ages.
Some types of glass that do not include silica as a major constituent may have physico-chemical properties useful for their application in fiber optics and other specialized technical applications. These include fluoride glass, aluminate and aluminosilicate glass, phosphate glass, borate glass, and chalcogenide glass.
There are three classes of components for oxide glass: network formers, intermediates, and modifiers. The network formers (silicon, boron, germanium) form a highly cross-linked network of chemical bonds. The intermediates (titanium, aluminium, zirconium, beryllium, magnesium, zinc) can act as both network formers and modifiers, according to the glass composition. The modifiers (calcium, lead, lithium, sodium, potassium) alter the network structure; they are usually present as ions, compensated by nearby non-bridging oxygen atoms, bound by one covalent bond to the glass network and holding one negative charge to compensate for the positive ion nearby. Some elements can play multiple roles; e.g. lead can act both as a network former (Pb4+ replacing Si4+), or as a modifier.
The presence of non-bridging oxygens lowers the relative number of strong bonds in the material and disrupts the network, decreasing the viscosity of the melt and lowering the melting temperature.
The alkali metal ions are small and mobile; their presence in glass allows a degree of electrical conductivity, especially in molten state or at high temperature. Their mobility decreases the chemical resistance of the glass, allowing leaching by water and facilitating corrosion. Alkaline earth ions, with their two positive charges and requirement for two non-bridging oxygen ions to compensate for their charge, are much less mobile themselves and also hinder diffusion of other ions, especially the alkalis. The most common commercial glass types contain both alkali and alkaline earth ions (usually sodium and calcium), for easier processing and satisfying corrosion resistance. Corrosion resistance of glass can be increased by dealkalization, removal of the alkali ions from the glass surface by reaction with sulfur or fluorine compounds. Presence of alkaline metal ions has also detrimental effect to the loss tangent of the glass, and to its electrical resistance; glass manufactured for electronics (sealing, vacuum tubes, lamps ...) have to take this in account.
Addition of lead(II) oxide lowers melting point, lowers viscosity of the melt, and increases refractive index. 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 in the matrix 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). For more details, see lead glass.
Addition of fluorine lowers the dielectric constant of glass. Fluorine is highly electronegative and attracts the electrons in the lattice, lowering the polarizability of the material. Such silicon dioxide-fluoride is used in manufacture of integrated circuits as an insulator. High levels of fluorine doping lead to formation of volatile SiF2O and such glass is then thermally unstable. Stable layers were achieved with dielectric constant down to about 3.5–3.7.
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. This was initially termed "splat cooling" by doctoral student W. Klement at Caltech, who showed that cooling rates on the order of millions of degrees per second is sufficient to impede the formation of crystals, and the metallic atoms become "locked into" a glassy state. 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.
Electrolytes or molten salts are mixtures of different ions. 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. The best-studied example is 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.
Some aqueous solutions can be supercooled into a glassy state, for instance LiCl:RH2O (a solution of lithium chloride salt and water molecules) in the composition range 4<R<8. An aqueous solution containing sugar has a glassy state and can be used as a surfactant.
A molecular liquid is composed of molecules that do not form a covalent network but interact only through weak van der Waals forces or through transient hydrogen bonds. Many molecular liquids can be supercooled into a glass; some are excellent glass formers that normally do not crystallize.
Under extremes of pressure and temperature solids may exhibit large structural and physical changes that can lead to polyamorphic phase transitions. In 2006 Italian scientists created an amorphous phase of carbon dioxide using extreme pressure. The substance was named amorphous carbonia(a-CO2) and exhibits an atomic structure resembling that of silica.
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.
In cell biology, there is recent evidence suggesting that the cytoplasm behaves like a colloidal glass approaching the liquid-glass transition. During periods of low metabolic activity, as in dormancy, the cytoplasm vitrifies and prohibits the movement to larger cytoplasmic particles while allowing the diffusion of smaller ones throughout the cell.
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.
As in other amorphous solids, the atomic structure of a glass lacks the long-range periodicity observed in crystalline solids. Due to chemical bonding characteristics, glasses do possess a high degree of short-range order with respect to local atomic polyhedra.
In physics, the standard definition of a glass (or vitreous solid) is a solid formed by rapid melt quenching, although the term glass is often used to describe any amorphous solid that exhibits a glass transition temperature Tg. 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.
Glass is an amorphous solid. It exhibits an atomic structure close to that observed in the supercooled liquid phase but displays all the mechanical properties of a solid. 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 of amorphous materials). Laboratory measurements of room temperature glass flow do show a motion consistent with a material viscosity on the order of 1017–1018 Pa s.
Although the atomic structure of glass shares characteristics of the structure in a supercooled liquid, glass tends to behave as a solid below its glass transition temperature. A supercooled liquid behaves as a liquid, but it is below the freezing point of the material, and in some cases will crystallize almost instantly if a crystal is added as a core. The change in heat capacity at a glass transition and a melting transition of comparable materials are typically of the same order of magnitude, indicating that the change in active degrees of freedom is comparable as well. Both in a glass and in a crystal it is mostly only the vibrational degrees of freedom that remain active, whereas rotational and translational motion is arrested. This helps to explain why both crystalline and non-crystalline solids exhibit rigidity on most experimental time scales.
|Unsolved problem in physics :|
What is the nature of the transition between a fluid or regular solid and a glassy phase? "The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition." —P.W. Anderson(more unsolved problems in physics )
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. The reason for the observation is that in the past, when panes of glass were commonly made by glassblowers, the technique used was to spin molten glass so as to create a round, mostly flat and even plate (the crown glass process, described above). This plate was then cut to fit a window. The pieces were not absolutely flat; the edges of the disk became a different thickness as the glass spun. When installed in a window frame, the glass would be placed with the thicker side down both for the sake of stability and to prevent water accumulating in the lead cames at the bottom of the window. Occasionally, such glass has been found installed with the thicker side at the top, left or right.
Mass production of glass window panes in the early twentieth century caused a similar effect. In glass factories, molten glass was poured onto a large cooling table and allowed to spread. The resulting glass is thicker at the location of the pour, located at the center of the large sheet. These sheets were cut into smaller window panes with nonuniform thickness, typically with the location of the pour centered in one of the panes (known as "bull's-eyes") for decorative effect. Modern glass intended for windows is produced as float glass and is very uniform in thickness.
Several other points can be considered that contradict the "cathedral glass flow" theory:
Art Nouveau (; French: [aʁ nuvo]) is an international style of art, architecture and applied art, especially the decorative arts, that was most popular between 1890 and 1910. A reaction to the academic art of the 19th century, it was inspired by natural forms and structures, particularly the curved lines of plants and flowers.
English uses the French name Art Nouveau (new art). The style is related to, but not identical with, styles that emerged in many countries in Europe at about the same time: in Austria it is known as Secessionsstil after Wiener Secession; in Spanish Modernismo; in Catalan Modernisme; in Czech Secese; in Danish Skønvirke or Jugendstil; in German Jugendstil, Art Nouveau or Reformstil; in Hungarian Szecesszió; in Italian Art Nouveau, Stile Liberty or Stile floreale; in Latvian Jūgendstils; in Lithuanian Modernas; in Norwegian Jugendstil; in Polish Secesja; in Slovak Secesia; in Ukrainian and Russian Модерн (Modern); in Swedish and Finnish Jugend.
Art Nouveau is a total art style: It embraces a wide range of fine and decorative arts, including architecture, painting, graphic art, interior design, jewelry, furniture, textiles, ceramics, glass art, and metal work.
By 1910, Art Nouveau was already out of style. It was replaced as the dominant European architectural and decorative style first by Art Deco and then by Modernism.Corrosion
Corrosion is a natural process, which converts a refined metal to a more chemically-stable form, such as its oxide, hydroxide, or sulfide. It is the gradual destruction of materials (usually metals) by chemical and/or electrochemical reaction with their environment. Corrosion engineering is the field dedicated to controlling and stopping corrosion.
In the most common use of the word, this means electrochemical oxidation of metal in reaction with an oxidant such as oxygen or sulfates. Rusting, the formation of iron oxides, is a well-known example of electrochemical corrosion. This type of damage typically produces oxide(s) or salt(s) of the original metal, and results in a distinctive orange colouration. Corrosion can also occur in materials other than metals, such as ceramics or polymers, although in this context, the term "degradation" is more common. Corrosion degrades the useful properties of materials and structures including strength, appearance and permeability to liquids and gases.
Many structural alloys corrode merely from exposure to moisture in air, but the process can be strongly affected by exposure to certain substances. Corrosion can be concentrated locally to form a pit or crack, or it can extend across a wide area more or less uniformly corroding the surface. Because corrosion is a diffusion-controlled process, it occurs on exposed surfaces. As a result, methods to reduce the activity of the exposed surface, such as passivation and chromate conversion, can increase a material's corrosion resistance. However, some corrosion mechanisms are less visible and less predictable.Fiberglass
Fiberglass (US) or fibreglass (UK) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet (called a chopped strand mat), or woven into a fabric. The plastic matrix may be a thermoset polymer matrix—most often based on thermosetting polymers such as epoxy, polyester resin, or vinylester—or a thermoplastic.
Cheaper and more flexible than carbon fiber, it is stronger than many metals by weight, and can be molded into complex shapes. Applications include aircraft, boats, automobiles, bath tubs and enclosures, swimming pools, hot tubs, septic tanks, water tanks, roofing, pipes, cladding, casts, surfboards, and external door skins.
Other common names for fiberglass are glass-reinforced plastic (GRP), glass-fiber reinforced plastic (GFRP) or GFK (from German: Glasfaserverstärkter Kunststoff). Because glass fiber itself is sometimes referred to as "fiberglass", the composite is also called "fiberglass reinforced plastic". This article will adopt the convention that "fiberglass" refers to the complete glass fiber reinforced composite material, rather than only to the glass fiber within it.Glass ceiling
A glass ceiling is a metaphor used to represent an invisible barrier that keeps a given demographic (typically applied to minorities) from rising beyond a certain level in a hierarchy.The metaphor was first coined by feminists in reference to barriers in the careers of high-achieving women. In the US, the concept is sometimes extended to refer to obstacles hindering the advancement of minority women, as well as minority men. Minority women often find the most difficulty in "breaking the glass ceiling" because they lie at the intersection of two historically marginalized groups: women and people of color. East Asian and East Asian American news outlets have coined the term "bamboo ceiling" to refer to the obstacles that all East Asian Americans face in advancing their careers.Within the same concepts of the other terms surrounding the workplace, there are similar terms for restrictions and barriers concerning women and their roles within organizations and how they coincide with their maternal duties. These "Invisible Barriers" function as metaphors to describe the extra circumstances that women undergo, usually when trying to advance within areas of their careers and often while trying to advance within their lives outside their work spaces.Google Glass
Google Glass is a brand of smart glasses—an optical head-mounted display designed in the shape of a pair of eyeglasses. It was developed by X (previously Google X) with the mission of producing a ubiquitous computer. Google Glass displayed information in a smartphone-like, hands-free format. Wearers communicated with the Internet via natural language voice commands.Google started selling a prototype of Google Glass to qualified "Glass Explorers" in the US on April 15, 2013, for a limited period for $1,500, before it became available to the public on May 15, 2014. It had an integral 5 megapixel still/720p video camera. The headset received a great deal of criticism and legislative action due to privacy and safety concerns.
On January 15, 2015, Google announced that it would stop producing the Google Glass prototype, to be continued in 2017 tentatively. In July 2017, it was announced that the Google Glass Enterprise Edition would be released.Kristallnacht
Kristallnacht (German pronunciation: [kʁɪsˈtalnaχt]; lit. "Crystal Night") or Reichskristallnacht (German: [ˌʁaɪçs.kʁɪsˈtalnaχt] (listen)), also referred to as the Night of Broken Glass, Reichspogromnacht [ˌʁaɪçs.poˈɡʁoːmnaχt] or simply Pogromnacht [poˈɡʁoːmnaχt] (listen), and Novemberpogrome [noˈvɛmbɐpoɡʁoːmə] (listen) (Yiddish: קרישטאָל נאַכט krishtol nakht), was a pogrom against Jews throughout Nazi Germany on 9–10 November 1938, carried out by SA paramilitary forces and civilians. The German authorities looked on without intervening. The name Kristallnacht comes from the shards of broken glass that littered the streets after the windows of Jewish-owned stores, buildings, and synagogues were smashed.
Estimates of the number of fatalities caused by the pogrom have varied. Early reports estimated that 91 Jews were murdered during the attacks. Modern analysis of German scholarly sources by historians such as Sir Richard Evans puts the number much higher. When deaths from post-arrest maltreatment and subsequent suicides are included, the death toll climbs into the hundreds. Additionally, 30,000 Jewish men were arrested and incarcerated in concentration camps.Jewish homes, hospitals, and schools were ransacked, as the attackers demolished buildings with sledgehammers. The rioters destroyed 267 synagogues throughout Germany, Austria, and the Sudentenland, and over 7,000 Jewish businesses were either destroyed or damaged. The British historian Martin Gilbert wrote that no event in the history of German Jews between 1933 and 1945 was so widely reported as it was happening, and the accounts from the foreign journalists working in Germany sent shock waves around the world. The British newspaper The Times wrote at the time: "No foreign propagandist bent upon blackening Germany before the world could outdo the tale of burnings and beatings, of blackguardly assaults on defenseless and innocent people, which disgraced that country yesterday."The attacks were retaliation for the assassination of the Nazi German diplomat Ernst vom Rath by Herschel Grynszpan, a seventeen-year-old German-born Polish Jew living in Paris. Kristallnacht was followed by additional economic and political persecution of Jews, and it is viewed by historians as part of Nazi Germany's broader racial policy, and the beginning of the Final Solution and The Holocaust.Margarita
A margarita is a cocktail consisting of tequila, orange liqueur, and lime juice often served with salt on the rim of the glass. The drink is served shaken with ice (on the rocks), blended with ice (frozen margarita), or without ice (straight up). Although it has become acceptable to serve a margarita in a wide variety of glass types, ranging from cocktail and wine glasses to pint glasses and even large schooners, the drink is traditionally served in the eponymous margarita glass, a stepped-diameter variant of a cocktail glass or champagne coupe.Materials science
The interdisciplinary field of materials science, also commonly termed materials science and engineering is the design and discovery of new materials, particularly solids. The intellectual origins of materials science stem from the Enlightenment, when researchers began to use analytical thinking from chemistry, physics, and engineering to understand ancient, phenomenological observations in metallurgy and mineralogy. Materials science still incorporates elements of physics, chemistry, and engineering. As such, the field was long considered by academic institutions as a sub-field of these related fields. Beginning in the 1940s, materials science began to be more widely recognized as a specific and distinct field of science and engineering, and major technical universities around the world created dedicated schools of the study, within either the Science or Engineering schools, hence the naming.
Materials science is a syncretic discipline hybridizing metallurgy, ceramics, solid-state physics, and chemistry. It is the first example of a new academic discipline emerging by fusion rather than fission.Many of the most pressing scientific problems humans currently face are due to the limits of the materials that are available and how they are used. Thus, breakthroughs in materials science are likely to affect the future of technology significantly.Materials scientists emphasize understanding how the history of a material (its processing) influences its structure, and thus the material's properties and performance. The understanding of processing-structure-properties relationships is called the § materials paradigm. This paradigm is used to advance understanding in a variety of research areas, including nanotechnology, biomaterials, and metallurgy. Materials science is also an important part of forensic engineering and failure analysis – investigating materials, products, structures or components which fail or do not function as intended, causing personal injury or damage to property. Such investigations are key to understanding, for example, the causes of various aviation accidents and incidents.Mirror
A mirror is an object that reflects light in such a way that, for incident light in some range of wavelengths, the reflected light preserves many or most of the detailed physical characteristics of the original light, called specular reflection. This is different from other light-reflecting objects that do not preserve much of the original wave signal other than color and diffuse reflected light, such as flat-white paint.
The most familiar type of mirror is the plane mirror, which has a flat surface. Curved mirrors are also used, to produce magnified or diminished images or focus light or simply distort the reflected image.
Mirrors are commonly used for personal grooming or admiring oneself (where they are also called looking-glasses), for viewing the area behind and on the sides on motor vehicles while driving, for decoration, and architecture. Mirrors are also used in scientific apparatus such as telescopes and lasers, cameras, and industrial machinery. Most mirrors are designed for visible light; however, mirrors designed for other wavelengths of electromagnetic radiation are also used.Nail clubbing
Nail clubbing, also known as digital clubbing, is a deformity of the finger or toe nails associated with a number of diseases, mostly of the heart and lungs. Clubbing for no obvious reason can also occur, but is rare. Hippocrates was the first to formally document clubbing as a sign of disease, and the phenomenon is therefore occasionally called "Hippocratic fingers."Obsidian
Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock.Obsidian is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth. It is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where the chemical composition (high silica content) causes a high viscosity which, upon rapid cooling, forms a natural glass from the lava. The inhibition of atomic diffusion through this highly viscous lava explains the lack of crystal growth. Obsidian is hard, brittle, and amorphous; it therefore fractures with very sharp edges. In the past it was used to manufacture cutting and piercing tools and it has been used experimentally as surgical scalpel blades.Optical fiber
An optical fiber is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths (data rates) than electrical cables. Fibers are used instead of metal wires because signals travel along them with less loss; in addition, fibers are immune to electromagnetic interference, a problem from which metal wires suffer excessively. Fibers are also used for illumination and imaging, and are often wrapped in bundles so they may be used to carry light into, or images out of confined spaces, as in the case of a fiberscope. Specially designed fibers are also used for a variety of other applications, some of them being fiber optic sensors and fiber lasers.Optical fibers typically include a core surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by the phenomenon of total internal reflection which causes the fiber to act as a waveguide. Fibers that support many propagation paths or transverse modes are called multi-mode fibers, while those that support a single mode are called single-mode fibers (SMF). Multi-mode fibers generally have a wider core diameter and are used for short-distance communication links and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 1,000 meters (3,300 ft).Being able to join optical fibers with low loss is important in fiber optic communication. This is more complex than joining electrical wire or cable and involves careful cleaving of the fibers, precise alignment of the fiber cores, and the coupling of these aligned cores. For applications that demand a permanent connection a fusion splice is common. In this technique, an electric arc is used to melt the ends of the fibers together. Another common technique is a mechanical splice, where the ends of the fibers are held in contact by mechanical force. Temporary or semi-permanent connections are made by means of specialized optical fiber connectors.The field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics. The term was coined by Indian physicist Narinder Singh Kapany, who is widely acknowledged as the father of fiber optics.Philip Glass
Philip Glass (born January 31, 1937) is an American composer. He is widely regarded as one of the most influential musicians of the late 20th century. Glass's work has been described as minimal music, having similar qualities to other "minimalist" composers such as La Monte Young, Steve Reich, and Terry Riley. Glass describes himself as a composer of "music with repetitive structures", which he has helped evolve stylistically.Glass founded the Philip Glass Ensemble, with which he still performs on keyboards. He has written numerous operas and musical theatre works, twelve symphonies, eleven concertos, eight string quartets and various other chamber music, and film scores. Three of his film scores have been nominated for Academy Awards.Poly(methyl methacrylate)
Poly(methyl methacrylate) (PMMA), also known as acrylic, acrylic glass, or plexiglass as well as by the trade names Crylux, Plexiglas, Acrylite, Lucite, and Perspex among several others (see below), is a transparent thermoplastic often used in sheet form as a lightweight or shatter-resistant alternative to glass. The same material can be used as a casting resin, in inks and coatings, and has many other uses.
Although not a type of familiar silica-based glass, the substance, like many thermoplastics, is often technically classified as a type of glass (in that it is a non-crystalline vitreous substance) hence its occasional historical designation as acrylic glass. Chemically, it is the synthetic polymer of methyl methacrylate. The material was developed in 1928 in several different laboratories by many chemists, such as William Chalmers, Otto Röhm, and Walter Bauer, and was first brought to market in 1933 by German Röhm & Haas AG (as of January 2019 part of Evonik Industries) and its partner and former U.S. affiliate Rohm and Haas Company under the trademark Plexiglas.PMMA is an economical alternative to polycarbonate (PC) when tensile strength, flexural strength, transparency, polishability, and UV tolerance are more important than impact strength, chemical resistance and heat resistance. Additionally, PMMA does not contain the potentially harmful bisphenol-A subunits found in polycarbonate. It is often preferred because of its moderate properties, easy handling and processing, and low cost. Non-modified PMMA behaves in a brittle manner when under load, especially under an impact force, and is more prone to scratching than conventional inorganic glass, but modified PMMA is sometimes able to achieve high scratch and impact resistance.Stained glass
The term stained glass can refer to coloured glass as a material or to works created from it. Throughout its thousand-year history, the term has been applied almost exclusively to the windows of churches and other significant religious buildings. Although traditionally made in flat panels and used as windows, the creations of modern stained glass artists also include three-dimensional structures and sculpture. Modern vernacular usage has often extended the term "stained glass" to include domestic leadlight and objets d'art created from foil glasswork exemplified in the famous lamps of Louis Comfort Tiffany.
As a material stained glass is glass that has been coloured by adding metallic salts during its manufacture. The coloured glass is crafted into stained glass windows in which small pieces of glass are arranged to form patterns or pictures, held together (traditionally) by strips of lead and supported by a rigid frame. Painted details and yellow stain are often used to enhance the design. The term stained glass is also applied to windows in which the colours have been painted onto the glass and then fused to the glass in a kiln.
Stained glass, as an art and a craft, requires the artistic skill to conceive an appropriate and workable design, and the engineering skills to assemble the piece. A window must fit snugly into the space for which it is made, must resist wind and rain, and also, especially in the larger windows, must support its own weight. Many large windows have withstood the test of time and remained substantially intact since the Late Middle Ages. In Western Europe they constitute the major form of pictorial art to have survived. In this context, the purpose of a stained glass window is not to allow those within a building to see the world outside or even primarily to admit light but rather to control it. For this reason stained glass windows have been described as "illuminated wall decorations".
The design of a window may be abstract or figurative; may incorporate narratives drawn from the Bible, history, or literature; may represent saints or patrons, or use symbolic motifs, in particular armorial. Windows within a building may be thematic, for example: within a church – episodes from the life of Christ; within a parliament building – shields of the constituencies; within a college hall – figures representing the arts and sciences; or within a home – flora, fauna, or landscape.
Stained glass is still popular today, but often referred to as art glass. It is prevalent in luxury homes, commercial buildings, and places of worship. Artists and companies are contracted to create beautiful art glass ranging from domes, windows, backsplashes, etc.The Crystal Palace
The Crystal Palace was a cast-iron and plate-glass structure originally built in Hyde Park, London, to house the Great Exhibition of 1851. The exhibition took place from 1 May until 15 October 1851, and more than 14,000 exhibitors from around the world gathered in its 990,000 square feet (92,000 m2) exhibition space to display examples of technology developed in the Industrial Revolution. Designed by Joseph Paxton, the Great Exhibition building was 1,851 feet (564 m) long, with an interior height of 128 feet (39 m). It was three times the size of St Paul's Cathedral.The introduction of the sheet glass method into Britain by Chance Brothers in 1832 made possible the production of large sheets of cheap but strong glass, and its use in the Crystal Palace created a structure with the greatest area of glass ever seen in a building. It astonished visitors with its clear walls and ceilings that did not require interior lights.
It has been suggested that the name of the building resulted from a piece penned by the playwright Douglas Jerrold, who in July 1850 wrote in the satirical magazine Punch about the forthcoming Great Exhibition, referring to a "palace of very crystal".After the exhibition, the Palace was relocated to an area of South London known as Penge Common. It was rebuilt at the top of Penge Peak next to Sydenham Hill, an affluent suburb of large villas. It stood there for 82 years from 1854 until its destruction by fire in November 1936. The nearby residential area was renamed Crystal Palace after the landmark. This included the Crystal Palace Park that surrounds the site, home of the Crystal Palace National Sports Centre, which had previously been a football stadium that hosted the FA Cup Final between 1895 and 1914. Crystal Palace F.C. were founded at the site in 1905 and played at the Cup Final venue in their early years. The park still contains Benjamin Waterhouse Hawkins's Crystal Palace Dinosaurs which date back to 1854.The Revenant (2015 film)
The Revenant is a 2015 American semi-biographical epic western film directed by Alejandro G. Iñárritu. The screenplay by Mark L. Smith and Iñárritu is based in part on Michael Punke's 2002 novel of the same name, describing frontiersman Hugh Glass's experiences in 1823. That novel is in turn based on the 1915 poem The Song of Hugh Glass. The film stars Leonardo DiCaprio, Tom Hardy, Domhnall Gleeson, and Will Poulter.
Development began in August 2001 when producer Akiva Goldsman purchased Punke's manuscript. Iñárritu signed on to direct in August 2011 and in April 2014, after several delays due to other projects, Iñárritu confirmed that he was beginning work on The Revenant and that DiCaprio would play the lead role. Principal photography began in October 2014. Location and crew concerns delayed the film from May to August 2015.
The Revenant premiered at the TCL Chinese Theatre on December 16, 2015, and had a limited release on December 25, expanding on January 8, 2016. The film received largely positive reviews, and praise for its performances (particularly from DiCaprio and Hardy), direction, and cinematography. It won three Golden Globe Awards and five BAFTA Awards. At the 88th Academy Awards, the film received 12 nominations, including Best Picture and Best Supporting Actor for Hardy, with Iñárritu, DiCaprio, and Emmanuel Lubezki winning the awards for Best Director, Best Actor, and Best Cinematography, respectively. DiCaprio also won the Golden Globe, Screen Actors Guild Award, BAFTA, and Critics' Choice Award for Best Actor.The Shard
The Shard, also infrequently referred to as the Shard of Glass, Shard London Bridge and formerly London Bridge Tower, is a 95-story supertall skyscraper, designed by the Italian architect Renzo Piano, in Southwark, London, that forms part of the Shard Quarter development. Standing 309.7 metres (1,016 ft) high, the Shard is the tallest building in the United Kingdom, the tallest building in the European Union, and the fifth-tallest building in Europe. It is also the second-tallest free-standing structure in the United Kingdom, after the concrete tower of the Emley Moor transmitting station. It replaced Southwark Towers, a 24-story office block built on the site in 1975.
The Shard's construction began in March 2009; it was topped out on 30 March 2012 and inaugurated on 5 July 2012. Practical completion was achieved in November 2012. The tower's privately operated observation deck, The View from The Shard, was opened to the public on 1 February 2013. The glass-clad pyramidal tower has 72 habitable floors, with a viewing gallery and open-air observation deck on the 72nd floor, at a height of 244 metres (801 ft). The Shard was developed by Sellar Property Group on behalf of LBQ Ltd and is jointly owned by Sellar Property (5%) and the State of Qatar (95%). The Shard is managed by Real Estate Management (UK) Limited on behalf of the owners.Through the Looking-Glass
Through the Looking-Glass, and What Alice Found There (1871) (also known as "Alice through the Looking-Glass" or simply "Through the Looking-Glass") is a novel by Lewis Carroll and the sequel to Alice's Adventures in Wonderland (1865). Alice again enters a fantastical world, this time by climbing through a mirror into the world that she can see beyond it. There she finds that, just like a reflection, everything is reversed, including logic (running helps you remain stationary, walking away from something brings you towards it, chessmen are alive, nursery rhyme characters exist, etc) Through the Looking-Glass includes such verses as "Jabberwocky" and "The Walrus and the Carpenter", and the episode involving Tweedledum and Tweedledee. The mirror which inspired Carroll remains displayed in Charlton Kings.
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