Glossary of Terms
Below is a Glossary of Terms for use with Abrisa Technologies. To download a PDF of the glossary, click here.
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Acid Etching
This process for the decoration of glass involves the application of hydrofluoric acid to the glass surface. Hydrofluoric acid vapors or baths of hydrofluoric acid salts may be used to give glass a matte, frosted appearance (similar to that obtained by surface sandblasting), as found in lighting glass. Glass designs can be produced by coating the glass with wax and then inscribing the desired pattern through the wax layer. When applied, the acid will corrode the glass but not attack the wax-covered areas.
Alumina-silicate Glass
Alumina (aluminum oxide Al2O3) is added to the glass batch in the form of commonly found feldspars containing alkalis in order to help improve chemical resistance and mechanical strength, and to increase viscosity at lower temperatures.
Annealing
Under natural conditions, the surface of molten glass will cool more rapidly than the center. This results in internal stresses which may cause the glass sheet or object to crack, shatter or even explode some time later. The annealing process is designed to eliminate or limit such stresses by submitting the glass to strictly controlled cooling in a special oven known as a “lehr”. Inside the lehr, the glass is allowed to cool to a temperature known as the “annealing point”. When the glass reaches this point, the lehr temperature is stabilized for a specific length of time (depending on the glass type, its thickness, its coefficient of expansion and the amount of residual stress required) to allow stresses present in the glass to relax. This phase is followed by a period of cooling with a pre-defined temperature gradient.
Anti-Reflective (AR) Glass
Anti-reflective glass is created by bonding specially selected optically designed coatings to the surface of the glass. The coating bonds to the surface of the glass cutting the surface reflectivity from approximately 4% to less than 0.1% in some cases. The purpose is reflection reduction, improving brightness or sharpening image contrast. A/R coatings can be specified on one or two sides.
Armor Plate Glass
Laminated glass, resistant to mechanical shock, composed of at least four panes of glass and usually at least 25 mm thick.
Beam Splitter
A beam splitter is an optical device that splits a beam of light in two. In its most common form, a cube made from two triangular glass prisms that are glued together at their base.
Beveling
The production, by abrasion, of a sloping edge on the glass sheet. Commonly used on mirror glass.
Borosilicate Glass
This glass all contains Boron as a component material. It is characterized by its resistance to heat, chemicals, and specific coefficients of thermal expansion. Borofloat® is a registered name for a type of borosilicate glass.
Bubbles
Gaseous inclusions in the glass melt which are removed by refining. Fining agents are introduced to encourage the formation of larger bubbles which rise more rapidly to the surface of the melt, attracting smaller bubbles on their way. Larger bubbles which are not removed by fining are known as “blisters”, smaller ones as “seeds” and longitudinally stretched bubbles as “air-lines”. Bubbles in glass are generally considered as defects but may also be intentionally created and used as a form of decoration.
Bulletproof Glass
Armor plate glass which is more than 60 mm thick and which resists penetration by bullets
Bus Bar
A bus bar is a thick strip of silver, chrome-nickel-gold, or silver epoxy that conducts electricity. Bus bars are used to carry very large currents, or to distribute current to multiple devices within switchgear or equipment.
Ceramic Glass
This glass is mechanically very strong material with almost no expansion or contraction when exposed to repeated and quick temperature changes, even up to 800-1000° C. Besides common uses such as CorningWare and ceramic stove tops, ceramic glass is used in electronics and sensors applications.
Cerium Oxide
The oxide of the rare earth, cerium, used alone or together with other substances as a polishing agent for glass.
Chemical Strengthening
This type of glass strengthening increases the thermal and mechanical strengths of glass without affecting the optical properties. This method is appropriate for thin glass, complex shaped parts or where minimal optical or mechanical distortion is desired. It is strengthened through an ion exchange process and produces up to 5 times the strength of annealed glass. Glass strengthened by this process will not “dice”.
Coating
A thin layer which covers the surface of an object. Coatings may be applied to glass in order to alter the appearance or performance of the product in question e.g. anti-reflective coatings applied to auto mirrors to aid vision, coatings with photocatalytic and hydrophilic properties to make self-cleaning windows.
Conductive Coating
A glass coating which is electrically conductive. Conductive coatings have been used to produce frost-free windshield, and in a range of electro-optical applications.
Cutting
The technique whereby glass is removed from the surface of an object by grinding it with a rotating wheel made of stone, wood, or metal, and an abrasive suspended in liquid.
Diamond Tool
Natural and synthetic diamonds are used on drills, saws, cutting wheels, abrasive discs and belts. The higher cutting rates achievable than with previous tools have stimulated the development of very precise, high-speed machinery. A constant flow of coolant is required to avoid the diamonds burning out and to wash away glass particles which build up on the working surface of the tool.
Diamond Wheels
Abrasive tools coated with diamond powder, used for a range of operations including grinding, milling, sawing, drilling, edging, and polishing.
Dichroic Filters
Dichroic filters are most commonly 1.75mm, coated on Borofloat glass, and useful when high heat resistance is required. Color filters can be heat treated up to 152mm diameter for additional heat resistance. These work by blocking out certain color wavelengths of light. Both type of filters can help control temperature, enhance or change light colors. These filters are used mainly in lighting applications.
Drawn Glass
A process for making sheet glass by drawing the molten glass as a sheet directly from the furnace. The thickness of the glass is determined by the drawing rate.
Edging
The shaping or finishing of the edges of a glass surface, usually by grinding with an abrasive wheel.
Fabricated Glass
This describes the customization of glass for the OEM market. It could include strengthening, coatings, machining, cutting, edging, surface grinding, polishing, specialty packaging.
Fire-Resisting Glass
Flat glass with a wire inlay which helps retard shattering in the event of fire and thus delays the spread of smoke and flames. Such glazing is classified as class G (which resists fire and prevents the spread of smoke and flames for specified periods of time) or class F (which has the characteristics of class G but also impedes the spreading of radiant heat for specified periods). New developments include pre-stressed wire-free borosilicate glass and double glazing with the inner space filled with an intumescent material which acts as a heat shield.
Firing
The process of bringing a glass furnace up to its operational temperature and then maintaining the temperature.
Flat Glass
All types of glass (rolled, float, plate, etc.) produced in a flat form, regardless of the method of production.
Float Glass
Float glass is a name for common window or plate glass. It is named float glass because the most common method for producing glass is using molten tin, where the molten glass floats on top of the tin, thus giving the name “float glass”. It is graded to meet specific applications from commercial to optical quality.
Float Process
A method for the production of high-quality sheet glass whereby a ribbon of molten glass is fed across a bath of heated liquid, usually molten tin, in a carefully controlled atmosphere.
Frit
Batch material that is melted with other materials and then ground into powder form before being added to the batch. Lead oxide, which can produce harmful dust, may be melted with silica, for example, and then ground down as a lead silicate.
Front Surface Mirror
This is a special glass with a mirror coating on the front surface of the glass. These can meet specific reflectivity, flatness, thickness requirements. Additional coatings such as anti-reflective coatings may also be applied. These mirrors are primarily used in rear projection display applications, television, photography, as well as special applications in the optical field.
Frosting
The process of giving a glass surface a matte finish, thus reducing transparency. Frosting may be done by a means of acid treatment (pouring hydrofluoric acid onto the glass), sandblasting, special glue applications and subsequent removal, or mechanical etching with a grinding wheel.
Furnace
An enclosed structure for the production and application of heat. In glassmaking, furnaces are used for melting the batch, maintaining pots of glass in a molten state, and reheating partly formed objects at the glory hole.
Fused Silica/Quartz
A single-component glass (SiO2) with very low thermal expansion, great thermal stability and very high ultraviolet transmission. The glass is expensive and difficult to produce since it has to be melted at 2,000°C.
Fusing
(1) The process of founding or melting the batch; (2) heating pieces of glass in a kiln or furnace until they bond; (3) heating enameled glass s until the enamel bonds with the surface of the object.
Fusing Glass-to-Glass
Glasses of different compositions can be fused together for decorative purposes and also in the sealing of electrical, medical, and industrial components. The fusion temperature for soda-lime glasses is generally between 760°C and 820°C. Particular attention must be paid to the thermal expansion coefficients of different glass types.
Glass
A homogeneous material with a random, liquid-like (non-crystalline) molecular structure. The manufacturing process requires that raw materials be heated to a temperature sufficient to produce a completely used melt, which, when cooled rapidly, becomes rigid without crystalizing.
Glass-ceramics
Materials produced from glass that have a polycrystalline structure. Most offer advantages of low thermal expansion, making them suitable for uses such as cookware. Others have high physical strength and can be machined like metals.
Glass Coating
These are just what they say: they coat the glass to provide added features and benefits to glass. There are standard coatings as well as custom coatings. Each coating has specific characteristics which must be matched to the glass substrate and the desired end result.
Grinding
The removal of glass with abrasives or abrasive (grinding) wheels in order to shape, polish, or otherwise finish both flat and hollow glass. Grinding processes include milling, sawing, edging, and drilling.
Heat Resistant Glass
Glass which has a low coefficient of expansion and which is therefore less liable to thermal shock. Borosilicate glass is the most common type of heat resistant glass.
Hot Mirror and Cold Mirror
Hot Mirrors reflect UV light while allowing visible light to be transmitted. Common uses are lighting in museum displays, store windows, light sources where UV standards are specified.
Cold Mirrors reflect greater than 95% of visible light while transmitting 90% of the infrared light (heat energy). Common uses are movie projectors, photo copiers, dental illuminators.
Hydrophobic Coatings
Hydrophobic coatings are “water hating” these coatings bond with the glass to create a barrier against dirt, repelling dust, grease and liquid. The hydrophobic coating will not optically change the glass plate. It is extremely durable water repellant that not only repels water, but any other undesirable matter, including salt spray.
Hydrophylic Coatings
Hydrophilic coatings are “water loving” these coatings reduce distortion on optics by interacting positively with water, causing condensates to spread uniformly over the surface of the coated glass; sheeting water rather than forming droplets that scatter light.
Ion-Exchange, Strengthening
The principle on which the chemical pre-stressing of glass is based. Through ion exchange, the surface composition of the glass can be modified without altering the glasses inner structure. In a molten salt bath (of potassium, for example), larger alkali ions take the place of smaller ions (sodium, for example) in the glass surface. The resulting compression of the larger ions leads to greater toughening of the glass than is possible by thermal strengthening. Glass thus treated is used in particular in the aircraft industry and other sectors where safety is all-important.
Industrial Glass
This term describes glass fabrications supporting the industrial market sector. Some of the industrial applications include fabricated glass for: ATM machines, warehouse inventory barcode readers, mobile tracking units, bio-medical tools, security lighting, night vision products, and touch screens.
Index-Matched Indium Tin Oxide
Index-Matched ITO coatings provide a combination of low resistivity and extra transmission in the visible spectrum (400-700 mm) within an average transmittance of 94%.
Indium Tin Oxide (ITO)
ITO is a solid solution of indium(III) oxide (In2O3) and tin(IV) oxide (SnO2), typically 90% In2O3, 10% SnO2 by weight. It is transparent and colorless in thin layers while in bulk form it is yellowish to grey. In the infrared region of the spectrum it is a metal-like mirror. Indium tin oxide is one of the most widely used transparent conducting oxides because of its two chief properties, because of its electrical conductivity and optical transparency, as well as the ease with which it can be deposited as a thin film. Thin films of indium tin oxide are most commonly deposited on surfaces by electron beam evaporation, physical vapor deposition, or a range of sputter deposition techniques.
Laminated Glass
Laminated (or compound) glass consists of two or more sheets of glass with one or more viscous plastic layers “sandwiched” between the glass panes. The solid joining of the glasses takes place in a pressurized vessel called an autoclave. In the autoclave, under simultaneous heating of the already processed layers of glass and special plastic, lamination occurs. When laminated safety glass breaks, the pieces remain attached to the internal plastic layer and the glass remains transparent.
Low Emissivity Glass
Commonly known as “low-E” glass and often used in double and triple glazing units, this window glass has a special thin-film metallic or oxide coating which allows the passage of short-wave solar energy into a building but prevents long-wave energy produced by heating systems and lighting from escaping outside. Low-E glass thus allows light to enter while also providing thermal insulation.
Non-Glare Glass
Non-glare glass is specified when the goal is to reduce the percentage of reflected light. To achieve this, the surface of the glass is chemically etched to break up reflection patterns and scatter reflected light. Glare reduction can be specified on either single or double surfaces. It is available in several quality and etching levels: from picture frame quality to display quality, and from 1- to 140 gloss units.
Optical Coatings
This coating is a thin layer of material placed on a glass lens or mirror which alters the way light passes through, or is reflected off the glass. Precision optical coatings are used in applications requiring high quality light and image transmission, such as medical imaging, instrumentation, microscopy and such. The following are some of these types of coatings:
- Anti-reflective: for glare reduction, improved transmission
- Anti-fog: for reducing moisture build-up on glass
- Bandpass Filters: Transmission of specific wavelengths of lightwaves for a specific end result. Can be a shortpass or longpass filter.
- Cold Mirrors: Transmit IR and block some or all visible light. This filter is useful in applications to block heat transmission.
- Colored Filters: allow only certain wavelengths to pass through glass
- Conductive / Anti-static: light transmission with <20 ohms of receptivity
- Front or First Surface Mirrors: for image projection
- Heat Absorption or IR: blocks IR, but passes visible light
- Heat Reflection: Hot Mirrors, Infrared (IR) blocking filter
- ITO: provides light transmission of approximately 89% with <20 ohms of resistivity (check this definition)
- UV filters: controls the transmission of UV light. Abrisa has exclusive distributorship of Optivex™ UV Blocking Filter.
Optical Glass
Glass is termed “Optical Glass” when its properties are conducive to applications requiring high quality light transmission, and is pure and clear in appearance. This includes all applications concerned with the quality of imaging.
Plate Glass
Flat glass made by the casting or rolling of molten glass which is then mechanically ground and polished to produce a smooth and transparent sheet.
Polishing
Smoothing the surface of an object when it is cold by holding it against a rotating wheel fed with a fine abrasive. Glass can also be polished with hand-held tools.
Precision Glass
This is a high-technology glass that lighter, lower-density with advanced attributes and superior surface quality. The surfaces are clean, ultra-flat, and dimensionally stable. Common applications are leading edge displays, instrumentation, gauges, heavy equipment monitors and displays.
Polishing Wheels
Traditionally made of wood or bristle and more recently of cork, polyurethane and bonded cloth, these discs are used in conjunction with abrasive pastes to polish glass surfaces. Felt wheels with materials such as cerium oxide and other commercially-produced powders are now widely used for fine polishing. In the polishing process, the wheel is rotated at speed by means of a motor and applied to the glass to be polished.
Precision Glass
This is a high-technology glass that is lighter, lower-density with advanced attributes and superior surface quality. The surfaces are clean, ultra-flat, and dimensionally stable. Common applications are leading edge displays, instrumentation, gauges, heavy equipment monitors and displays.
Quartz/Fused Silica
These two types of glasses are virtually identical but have different methods of manufacture and slightly different material properties. They are used in applications where high ultraviolet light transmission, good thermal stability, or chemical inertness is required.
Advances in raw material beneficiation permit transparent fusions from sand as well as from crystal. When naturally occurring crystalline silica (sand or rock) is melted, the material is called fused quartz. When silicon dioxide is synthetically derived, the material is referred to as synthetic fused silica.
These materials can withstand temperatures to 1093° C. Abrisa Technologies offers several grades of Quartz and Fused Silica.
Refractive Index
A standard of measurement used particularly to establish the qualities of optical glass. The index is the ratio of the sine of the angle of incidence of a ray of light to the sine of the angle of refraction (the change in direction when a ray of light passes from one medium to another) by the glass. The second medium normally used to establish the index is a vacuum.
Rolled Glass
Rolled (or cast) glass is a translucent glass with 50-80% light transmission, depending on its thickness and type of surface. It is used where transparency of the glass sheet is not important or not desired. To produce rolled glass, molten glass pours from the melting tank over a refractory barrier (the “weir”) and onto the machine slab where it flows under a refractory gate (the “tweel”), which regulates the volume of glass, and then between two water-cooled rollers. The distance between the rollers determines the thickness of the glass.
Safety Glass
Glass which does not disintegrate into sharp and potentially dangerous splinters when it is broken. Safety glass may be produced by laminating or by tempering.
Sand Blasting
A method for giving glass surfaces a matt finish either for decoration or to reduce transparency. The method was invented in 1870 by an American, Benjamin C. Tilghman, who is thought to have been inspired by the effect of sand being blown against windows on the American prairies. Compressed air forces the abrasive material through the nozzle of a sandblasting gun and onto the glass surface. Although sand can be used, more effective abrasives with less toxic effects are now available. Silicon carbide is commonly used, as is electro-corundum (aluminum oxide). The glass is normally placed inside a special cabinet with arm holes, a viewing window and dust extraction facilities.
Sawing
The cutting and shaping of glass using a diamond blade mounted on a motorized saw.
Screen Printing
A process for the decoration of glass whereby colored ink is forced by a flexible “squeegee” through a fine-mesh screen, or “mask”, (traditionally made of silk, now also made of nylon, polyester and stainless steel) onto the glass surface. A separate mask is used for the application of each color. Considerable automation of the process has been developed, thus allowing extremely high printing speeds for even complex designs.
Soda-Lime Glass
The most common type of industrially produced glass. A typical soda-lime glass is composed of silica (71-75%), soda (12-16%) and lime (10-15%), plus small amounts of other materials to provide particular properties such as color.
Sputtering
The process in which, by passing an electric current through an ionized gas and thus bombarding the surface of a metal cathode with ions, atoms of the desired metal are vaporized and then deposited in a thin film on the surface of glass.
Technical Glass
This term describes sheet glass and flat glass with good optical properties and high thermal resistance. This glass is appropriate for optical coatings, electronic displays and components, sensor technology, biotechnology uses, and harsh environments.
Tempered Glass
This is a method of strengthening glass when small shards or “dicing” is required when the glass is broken. Heat tempering will cause some optical distortion.
Thin Glass
This glass is a clear technical glass made of very pure raw ingredients, and is characterized by low thermal expansion and thermal resistivity, good chemical resistance, high surface quality, good optical transmission, and flatness.
Toughening
Special process of solidification of a glass sheet in order to make it particularly resistant to breakages. The process may be physical (thermal) or chemical. In the former, the glass sheet is heated to a temperature just below its softening point and then immediately cooled by special jets of cold-air. These harden the surface of the glass, giving the inside more time to cool. This allows the external layer to crystallize into a wider lattice while the inside solidifies with greater compression than in the crystal lattice. The result is a sheet of glass which is two or three times stronger than untempered glass and which, upon breakage, shatters into tiny pieces with blunt edges (the most common applications are for automotive glass). The chemical process, on the other hand, is based on the so-called ion-stuffing technique. Different chemical elements possess different ionic radii and therefore different densities. Hence, if glass containing sodium is cooled slowly in a salt bath of molten potassium, the sodium ions will migrate from the glass to the salt, while the potassium ions will move to the surface of the glass where, due to their wider radium, they create a denser and therefore stronger surface layer (of no less than 0.1 mm). Glass sheets which have been chemically tempered are five to eight times stronger than those which have not undergone any tempering process.
Tubing
Made of borosilicate glass, tubing and rods can be cut to the required shape and size. Abrisa carries the entire SCHOTT line of tubing and rods.
Ultra-Violet Absorbing Glass
Ultra-violet radiation is absorbed by normal glass. Where ultra-violet transmission is required, quartz glass is used.
Vapor Deposition of Thin Films
The term covers a wide range of techniques for applying a thin film on the surface of the glass to change its technical or aesthetic properties e.g. scratch resistance, solar control. The methods employed to deposit the film include spraying onto hot glass, condensation in a vacuum and evaporation of the film material by heating.
Wafers
A wafer is a thin slice of semiconducting glass material, upon which microcircuits are constructed by combining various materials. Wafers are of key importance in the fabrication of semiconductor devices such as integrated circuits, and appropriate for micro optical products. Wafers are custom manufactured by size and thickness for each application.
