Borosilicate glass is a type of
glassGlass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
with the main glass-forming constituents
silicaThe chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...
and boron oxide. Borosilicate glasses are known for having very low coefficients of thermal expansion (~3 × 10
−6 /°C at 20°C), making them resistant to
thermal shockThermal shock is the name given to cracking as a result of rapid temperature change. Glass and ceramic objects are particularly vulnerable to this form of failure, due to their low toughness, low thermal conductivity, and high thermal expansion coefficients...
, more so than any other common glass. Such glass is less subject to thermal stress and is commonly used for the construction of
reagent bottleReagent bottles, also known as media bottles or graduated bottles, are containers made of glass, plastic, borosilicate or related substances, and topped by special caps or stoppers and are intended to contain chemicals in liquid or powder form for laboratories and stored in cabinets or on shelves...
s. Borosilicate glass is sold under such trade names as
PyrexPyrex is a brand name for glassware, introduced by Corning Incorporated in 1915.Originally, Pyrex was made from borosilicate glass. In the 1940s the composition was changed for some products to tempered soda-lime glass, which is the most common form of glass used in glass bakeware in the US and has...
and Kimax.
History
Borosilicate glass was first developed by German glassmaker
Otto SchottFriedrich Otto Schott was a German chemist, glass technologist, and the inventor of borosilicate glass. He was the son of a window glass maker, Simon Schott. From 1870 to 1873 Schott studied chemical technology at the technical college in Aachen and at the universities of Würzburg and Leipzig...
in the late 19th century and sold under the brand name "Duran" in 1893. After Corning Glass Works introduced
PyrexPyrex is a brand name for glassware, introduced by Corning Incorporated in 1915.Originally, Pyrex was made from borosilicate glass. In the 1940s the composition was changed for some products to tempered soda-lime glass, which is the most common form of glass used in glass bakeware in the US and has...
in 1915, the name became a synonym for borosilicate glass in the English-speaking world.
The European manufacturer of Pyrex, Arc International, uses borosilicate glass in its Pyrex glass kitchen products; however, the U.S. manufacturer of Pyrex kitchenware uses tempered
soda-lime glassSoda-lime glass, also called soda-lime-silica glass, is the most prevalent type of glass, used for windowpanes, and glass containers for beverages, food, and some commodity items...
. Thus Pyrex can refer to either soda-lime glass or borosilicate glass when discussing kitchen glassware, while Pyrex, Bomex, Duran and Kimax all refer to borosilicate glass when discussing
laboratory glasswareLaboratory glassware refers to a variety of equipment, traditionally made of glass, used for scientific experiments and other work in science, especially in chemistry and biology laboratories...
.
Most borosilicate glass is colorless. Colored borosilicate, for the studio glass trade, was first widely brought onto the market in 1986 when Paul Trautman founded Northstar Glassworks. In 2000, former Northstar Glassworks employee Henry Grimmett started
Glass AlchemyGlass Alchemy is a family run colored borosilicate glass company located in Portland, Oregon. Established in 2000, Glass Alchemy manufactures a number of handcrafted colored borosilicate glass products including, Boromax® rod, tube and frit and the customizable Tailor Made™ Tube...
and developed the first cadmium Crayon Colors and aventurine Sparkle colors in the borosilicate palette.
In addition to the
quartzQuartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
,
sodium carbonateSodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...
, and
calcium carbonateCalcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
traditionally used in glassmaking,
boronBoron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
is used in the manufacture of borosilicate glass. Typically, the resulting glass composition is about 70% silica, 10% boron oxide, 8%
sodium oxideSodium oxide is a chemical compound with the formula Na2O. It is used in ceramics and glasses, though not in a raw form. Treatment with water affords sodium hydroxide....
, 8%
potassium oxidePotassium oxide is an ionic compound of potassium and oxygen. This pale yellow solid, the simplest oxide of potassium, is a rarely encountered, highly reactive compound...
, and 1%
calcium oxideCalcium oxide , commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature....
(lime). Though somewhat more difficult to make than traditional glass (Corning conducted a major revamp of their operations to make it), it is economical to produce; its superior durability, chemical and heat resistance finds excellent use in
chemicalChemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
laboratoryA laboratory is a facility that provides controlled conditions in which scientific research, experiments, and measurement may be performed. The title of laboratory is also used for certain other facilities where the processes or equipment used are similar to those in scientific laboratories...
equipment, cookware, lighting and, in certain cases, windows.
Manufacturing process
Borosilicate glass is created by adding boron to the traditional glassmaker's
fritFrit is a ceramic composition that has been fused in a special fusing oven, quenched to form a glass, and granulated. Frits form an important part of the batches used in compounding enamels and ceramic glazes; the purpose of this pre-fusion is to render any soluble and/or toxic components insoluble...
of silicate
sandSand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
,
sodaSodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...
, and ground lime. Since borosilicate glass melts at a higher temperature than ordinary silicate glass, some new techniques were required for industrial production. Borrowing from the
weldingWelding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...
trade, burners combining
oxygenOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
with
natural gasNatural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
were required.
Physical characteristics
Borosilicate glass has a very low
thermal expansionThermal expansion is the tendency of matter to change in volume in response to a change in temperature.When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation. Materials which contract with increasing temperature are rare; this effect is...
coefficient (3.3 x 10
-6/K), about one-third that of ordinary glass. This reduces material stresses caused by temperature gradients which makes borosilicate the most suitable kind of glass for certain applications (see below).
The
softening pointThe softening point is the temperature at which a material softens beyond some arbitrary softness. It can be determined, for example, by the Vicat method , Heat Deflection Test or a ring and ball method ....
(temperature at which
viscosityViscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
is approximately
poise) of type 7740 Pyrex is 820 °C (1,508 °F).
Borosilicate glass is less
denseThe mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
than ordinary glass.
While more resistant to
thermal shockThermal shock is the name given to cracking as a result of rapid temperature change. Glass and ceramic objects are particularly vulnerable to this form of failure, due to their low toughness, low thermal conductivity, and high thermal expansion coefficients...
than other types of glass, borosilicate glass can still crack or shatter when subject to rapid or uneven temperature variations. When broken, borosilicate glass tends to crack into large pieces rather than shattering (it will snap rather than splinter).
Optically, borosilicate glasses are
crown glassesCrown glass is type of optical glass used in lenses and other optical components. It has relatively low refractive index and low dispersion...
with low dispersion (
Abbe numberIn physics and optics, the Abbe number, also known as the V-number or constringence of a transparent material, is a measure of the material's dispersion in relation to the refractive index...
s around 65) and relatively low
refractive indicesIn optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
(1.51–1.54 across the visible range).
Usage
Virtually all modern laboratory glassware is borosilicate glass. It is so widely used in this application due to its chemical and thermal resistance and good optical clarity, but the glass can be reacted with
sodium hydrideSodium hydride is the chemical compound with the empirical formula NaH. It is primarily used as a strong base in organic synthesis. NaH is representative of the saline hydrides, meaning it is a salt-like hydride, composed of Na+ and H− ions, in contrast to the more molecular hydrides such as...
to produce
sodium borohydrideSodium borohydride, also known as sodium tetrahydridoborate, is an inorganic compound with the formula NaBH4. This white solid, usually encountered as a powder, is a versatile reducing agent that finds wide application in chemistry, both in the laboratory and on a technical scale. Large amounts are...
, a common laboratory reducing agent.
Fused quartzFused quartz and fused silica are types of glass containing primarily silica in amorphous form. They are manufactured using several different processes...
is also found in some laboratory equipment when its higher melting point and transmission of UV are required (e.g. for tube furnace liners and UV cuvettes), but the cost and difficulty of working with quartz make it excessive for the majority of laboratory equipment.
During the mid-twentieth century, borosilicate glass tubing was used to pipe coolants (often
distilled waterDistilled water is water that has many of its impurities removed through distillation. Distillation involves boiling the water and then condensing the steam into a clean container.-History:...
) through high power
vacuum tubeIn electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
–based electronic equipment, such as commercial broadcast transmitters.
Glass cookware is another common usage. Borosilicate glass is used for measuring cups, featuring screen printed markings providing graduated measurements, which are widely used in American kitchens.
Aquarium heaters are sometimes made of borosilicate glass. Due to its high heat resistance, it can tolerate the significant temperature difference between the water and the
nichromeNichrome is a non-magnetic alloy of nickel, chromium, and often iron, usually used as a resistance wire. Patented in 1905, it is the oldest documented form of resistance heating alloy. A common alloy is 80% nickel and 20% chromium, by mass, but there are many others to accommodate various...
heating elementA heating element converts electricity into heat through the process of Joule heating. Electric current through the element encounters resistance, resulting in heating of the element....
.
Many high-quality flashlights use borosilicate glass for the lens. This allows for a higher percentage of light transmittance through the lens compared to plastics and lower-quality glass.
Several types of
High-Intensity DischargeHigh-intensity discharge lamps are a type of electrical lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube. This tube is filled with both gas and metal salts. The gas facilitates the...
(HID) lamps, such as
mercury vaporA mercury-vapor lamp is a gas discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger borosilicate glass bulb...
and metal halide lamps, use borosilicate glass as the outer envelope material.
Specialty marijuana and tobacco
pipesPipe smoking is the practice of tasting or inhaling the smoke produced by burning a substance, most commonly tobacco, in a pipe. It is the oldest traditional form of smoking.-History:...
are made from borosilicate glass. The high heat resistance makes the pipes more durable.
Most premanufactured glass
guitar slidesSlide guitar or bottleneck guitar is a particular method or technique for playing the guitar. The term slide refers to the motion of the slide against the strings, while bottleneck refers to the original material of choice for such slides: the necks of glass bottles...
are also made of borosilicate glass.
New
lampworkingLampworking is a type of glasswork that uses a gas fueled torch to melt rods and tubes of clear and colored glass. Once in a molten state, the glass is formed by blowing and shaping with tools and hand movements. It is also known as flameworking or torchworking, as the modern practice no longer...
techniques led to artistic applications such as contemporary glass
marbleA marble is a small spherical toy usually made from glass, clay, steel, or agate. These balls vary in size. Most commonly, they are about ½ inch in diameter, but they may range from less than ¼ inch to over 3 inches , while some art glass marbles fordisplay purposes are over 12 inches ...
s. The modern studio glass movement has responded to color. "The availability of colors began to increase when companies such as Glass Alchemy introduced the Crayon Colors, which brought a whole new vivacity to the glass industry." Borosilicate is commonly used in the
glassblowingGlassblowing is a glassforming technique that involves inflating molten glass into a bubble, or parison, with the aid of a blowpipe, or blow tube...
form of
lampworkingLampworking is a type of glasswork that uses a gas fueled torch to melt rods and tubes of clear and colored glass. Once in a molten state, the glass is formed by blowing and shaping with tools and hand movements. It is also known as flameworking or torchworking, as the modern practice no longer...
and the artists create a range of products ranging from jewelry,
kitchenwareKitchenware include utensils, appliances, dishes, cookware, and so on for use in the kitchen.-See also:*Cookware and bakeware*Dishware*Drinkware*List of eating utensils*List of food preparation utensils*List of Japanese cooking utensils...
, to
sculptureSculpture is three-dimensional artwork created by shaping or combining hard materials—typically stone such as marble—or metal, glass, or wood. Softer materials can also be used, such as clay, textiles, plastics, polymers and softer metals...
as well as for artistic glass tobacco pipes.
Borosilicate glass is sometimes used for high-quality beverage glassware. Borosilicate glass lends kitchen- and glassware increased durability along with microwave and dishwasher compatibility.
Most astronomical
reflecting telescopeA reflecting telescope is an optical telescope which uses a single or combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century as an alternative to the refracting telescope which, at that time, was a design that suffered from...
glass mirror components are made of borosilicate glass because of its low coefficient of expansion with heat. This makes very precise optical surfaces possible that change very little with temperature, and matched glass mirror components that "track" across temperature changes and retain the optical system's characteristics.
The optical glass most often used for making instrument
lensesA lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
is Schott BK-7 (or the equivalent from other makers), a very finely made borosilicate
crown glassCrown glass is type of optical glass used in lenses and other optical components. It has relatively low refractive index and low dispersion...
. It is also designated as 517642 glass after its 1.517 refractive index and 64.2
Abbe numberIn physics and optics, the Abbe number, also known as the V-number or constringence of a transparent material, is a measure of the material's dispersion in relation to the refractive index...
. Other less costly borosilicate glasses, such as Schott B270 or the equivalent, are used to make "
crown glassCrown glass is type of optical glass used in lenses and other optical components. It has relatively low refractive index and low dispersion...
" eyeglass lenses. Ordinary lower-cost borosilicate glass, like that used to make kitchenware and even reflecting telescope mirrors, cannot be used for high-quality lenses because of the striations and
inclusionsIn mineralogy, an inclusion is any material that is trapped inside a mineral during its formation.In gemology, an inclusion is a characteristic enclosed within a gemstone, or reaching its surface from the interior....
common to lower grades of this type of glass. The maximum working temperature is 515 fahrenheit. While it transitions to a liquid starting at 550 degrees fahrenheit(just before it turns red-hot), it is not workable until it reaches over 1000 fahrenheit. That means that in order to industrially produce this glass, oxygen/fuel torches must be used. Glassblowers borrowed technology and techniques from welders.
Borosilicate is also a material of choice for evacuated tube solar thermal technology, because of its high strength and heat resistance.
Borosilicate glasses also find application in the
semiconductor industryThe semiconductor industry is the aggregate collection of companies engaged in the design and fabrication of semiconductor devices. It formed around 1960, once the fabrication of semiconductors became a viable business...
in the development of
microelectromechanical systemsMicroelectromechanical systems is the technology of very small mechanical devices driven by electricity; it merges at the nano-scale into nanoelectromechanical systems and nanotechnology...
(MEMS), as part of stacks of
etchedEtching is used in microfabrication to chemically remove layers from the surface of a wafer during manufacturing. Etching is a critically important process module, and every wafer undergoes many etching steps before it is complete....
silica
wafersA wafer is a thin slice of semiconductor material, such as a silicon crystal, used in the fabrication of integrated circuits and other microdevices...
bonded to the etched borosilicate glass.
The
thermal insulation tilesThe Space Shuttle thermal protection system is the barrier that protects the Space Shuttle Orbiter during the searing heat of atmospheric reentry...
on the
Space ShuttleThe Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
were coated with a borosilicate glass.
Lighting manufacturers use borosilicate glass in their refractors.
Additionally, borosilicate tubing is used as the feedstock for the production of
parenteralParenteral is a route of administration that involves piercing the skin or mucous membrane. Parenteral nutrition refers to providing nutrition via the veins.-Etymology:...
drug packaging, such as vials and pre-filled
syringeA syringe is a simple pump consisting of a plunger that fits tightly in a tube. The plunger can be pulled and pushed along inside a cylindrical tube , allowing the syringe to take in and expel a liquid or gas through an orifice at the open end of the tube...
s, and is also used for the production of
ampouleAn ampoule is a small sealed vial which is used to contain and preserve a sample, usually a solid or liquid. Ampoules are commonly made of glass, although plastic ampoules do exist....
s and
dental cartridgesA dental syringe is a syringe used by dentists for the injection of an anesthetic. It consists of a breech-loading syringe fitted with a sealed cartridge containing anesthetic solution....
. The chemical resistance of borosilicate glass minimizes the migration of sodium ions from the glass matrix thus making it well suited for
injectable drugIn substance dependence and recreational drug use, drug injection is a method of introducing a drug into the body with a hollow needle and a syringe which is pierced through the skin into the body...
applications. This type of glass is typically referred to as USP / EP JP Type I.
Borosilicate glasses are used for immobilisation and disposal of
radioactive wasteRadioactive wastes are wastes that contain radioactive material. Radioactive wastes are usually by-products of nuclear power generation and other applications of nuclear fission or nuclear technology, such as research and medicine...
s. In most countries
high-level radioactive wasteHigh-level radioactive waste management concerns management and disposal of highly radioactive materials created during production of nuclear power and nuclear warheads. The technical issues in accomplishing this are daunting, due to the extremely long periods radioactive wastes remain deadly to...
has been incorporated into alkali borosilicate or phosphate vitreous waste forms for many years and vitrification is an established technology. Vitrification is a particularly attractive immobilization route because of the high chemical durability of the vitrified glass product. This characteristic has been used by industry for centuries. The chemical resistance of glass can allow it to remain in a corrosive environment for many thousands and even millions of years.
Borosilicate nanoparticles
It was initially thought that borosilicate glass could not be formed into
nanoparticleIn nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. Particles are further classified according to size : in terms of diameter, coarse particles cover a range between 10,000 and 2,500 nanometers. Fine particles are sized...
s, since an unstable boron oxide precursor prevented successful forming of these shapes. However, in 2008 a team of researchers from the Swiss
Federal Institute of TechnologyThe Swiss Federal Institute of Technology Zurich or ETH Zürich is an engineering, science, technology, mathematics and management university in the City of Zurich, Switzerland....
at
LausanneLausanne is a city in Romandy, the French-speaking part of Switzerland, and is the capital of the canton of Vaud. The seat of the district of Lausanne, the city is situated on the shores of Lake Geneva . It faces the French town of Évian-les-Bains, with the Jura mountains to its north-west...
were successful in forming borosilicate nanoparticles of 100 to 500 nanometers in diameter. The researchers formed a
gelA gel is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state...
of tetraethylorthosilicate and trimethoxyboroxine. When this gel is exposed to water under proper conditions, a dynamic reaction ensues which results in the nanoparticles.
In lampworking
Borosilicate, or "boro" (as it is often called), is used extensively in the
glassblowingGlassblowing is a glassforming technique that involves inflating molten glass into a bubble, or parison, with the aid of a blowpipe, or blow tube...
process
lampworkingLampworking is a type of glasswork that uses a gas fueled torch to melt rods and tubes of clear and colored glass. Once in a molten state, the glass is formed by blowing and shaping with tools and hand movements. It is also known as flameworking or torchworking, as the modern practice no longer...
; the glassworker uses a burner torch to melt and form glass, using a variety of metal and
graphiteThe mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...
tools to shape it. Borosilicate is referred to as "hard glass" and has a higher melting point than "soft glass," which is prefered for glassblowing. Raw glass used in lampworking comes in glass rods for solid work and glass tubes for hollow work tubes and vessels/containers. Lampworking is used to make complex and custom scientific apparatus; most major universities have a lampworking shop to manufacture and repair their glassware. For this kind of "scientific glassblowing", the specifications must be exact and the glassblower must be highly skilled and work with precision. Lampworking is also done as art and common items made include goblets, pipes, paper weights and pendants.
Beadmaking with Borosilicate Glass: In recent years, with the resurgence of lampworking as a technique to make handmade glass beads, boro has become a popular material in many glass artists' studios. Boro for beadmaking comes in thin, pencil-like rods.
Northstar is a popular brand, although there are several others that are also excellent. The metals used to color boro glass, particularly silver, often create striking beautiful and unpredictable results when melted in an oxygen-gas torch flame. Because it retains heat longer than soft glass, and because it is stronger than soft glass, boro is particulary suited for sculpting and creating large beads, including figurines. The tools used for making glass beads from boro glass are the same as those used for making glass beads from soft glass. Colored borosilicate lampworking glass is often considerably more expensive than "soft" lampworking glass, and this is usually reflected in the selling price of handmade artisan boro beads.
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