Glass

Glass is a non-crystalline solid that is often transparent, brittle and chemically inert. It has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics.

Glass is most often formed by rapid cooling (quenching) of the molten form; some glasses such as volcanic glass are naturally occurring. The most familiar, and historically the oldest, types of manufactured glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. Soda–lime glass, containing around 70% silica, accounts for around 90% of manufactured glass. The term glass, in popular usage, is often used to refer only to this type of material, although silica-free glasses often have desirable properties for applications in modern communications technology. Some objects, such as drinking glasses and eyeglasses, are so commonly made of silicate-based glass that they are simply called by the name of the material.

Despite being brittle, buried silicate glass will survive for very long periods if not disturbed, and many examples of glass fragments exist from early glassmaking cultures. Archaeological evidence suggests glassmaking dates back to at least 3600 BC in Mesopotamia, Egypt, or Syria. The earliest known glass objects were beads, perhaps created accidentally during metalworking or the production of faience. Due to its ease of formability into any shape, glass has been traditionally used for vessels, such as bowls, vases, bottles, jars and drinking glasses. In its most solid forms, it has also been used for paperweights and marbles. Glass can be coloured by adding metal salts or painted and printed with vitreous enamels, leading to its use in stained glass windows and other glass art objects. The refractive, reflective and transmission properties of glass make glass suitable for manufacturing optical lenses, prisms, and optoelectronics materials. Extruded glass fibres have application as optical fibres in communications networks, thermal insulating material when matted as glass wool so as to trap air, or in glass-fibre reinforced plastic (fibreglass).

## Occurrence in nature

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

## History

Naturally occurring obsidian glass was used by Stone Age societies as it fractures along very sharp edges, making it ideal for cutting tools and weapons. Glassmaking dates back at least 6000 years, long before humans had discovered how to smelt iron. Archaeological evidence suggests that the first true synthetic glass was made in Lebanon and the coastal north Syria, Mesopotamia or ancient Egypt. The earliest known glass objects, of the mid-third millennium BC, were beads, perhaps initially created as accidental by-products of metalworking (slags) or during the production of faience, a pre-glass vitreous material made by a process similar to glazing. Early glass was rarely transparent and often contained impurities and imperfections, and is technically faience rather than true glass, which did not appear until the 15th century BC. However, red-orange glass beads excavated from the Indus Valley Civilization dated before 1700 BC (possibly as early as 1900 BC) predate sustained glass production, which appeared around 1600 BC in Mesopotamia and 1500 BC in Egypt. During the Late Bronze Age there was a rapid growth in glassmaking technology in Egypt and Western Asia. Archaeological finds from this period include coloured glass ingots, vessels, and beads. Much early glass production relied on grinding techniques borrowed from stoneworking, such as grinding and carving glass in a cold state.

The term glass developed in the late Roman Empire. It was in the Roman glassmaking centre at Trier (located in current-day 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, as well as trade items in marketplaces in distant provinces. Examples of Roman glass have been found outside of the former Roman Empire in China, the Baltics, the Middle East, and India. The Romans perfected cameo glass, produced by etching and carving through fused layers of different colours to produce a design in relief on the glass object.

In post-classical West Africa, Benin was a manufacturer of glass and glass beads. Glass was used extensively in Europe during the Middle Ages. Anglo-Saxon glass has been found across England during archaeological excavations of both settlement and cemetery sites. 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. With the change in architectural style during the Renaissance period in Europe, the use of large stained glass windows became much less prevalent, although stained glass had a major revival with Gothic Revival architecture in the 19th century.

During the 13th century, the island of Murano, Venice, became a centre for glass making, building on medieval techniques to produce colourful ornamental pieces in large quantities. Murano glass makers developed the exceptionally clear colourless glass cristallo, so called for its resemblance to natural crystal, which was extensively used for windows, mirrors, ships' lanterns, and lenses. In the 13th, 14th, and 15th centuries, enamelling and gilding on glass vessels was perfected in Egypt and Syria. Towards the end of the 17th century, Bohemia became an important region for glass production, remaining so until the start of the 20th century. By the 17th century, glass in the Venetian tradition was also being produced in England. In about 1675, George Ravenscroft invented lead crystal glass, with cut glass becoming fashionable in the 18th century. Ornamental glass objects became an important art medium during the Art Nouveau period in the late 19th century.

Throughout the 20th century, new mass production techniques led to widespread availability of glass in much larger amounts, making it practical as a building material and enabling new applications of glass. In the 1920s a mould-etch process was developed, in which art was etched directly into the mould, so that each cast piece emerged from the mould with the image already on the surface of the glass. This reduced manufacturing costs and, combined with a wider use of coloured glass, led to cheap glassware in the 1930s, which later became known as Depression glass. In the 1950s, Pilkington Bros., England, developed the float glass process, producing high-quality distortion-free flat sheets of glass by floating on molten tin. Modern multi-story buildings are frequently constructed with curtain walls made almost entirely of glass. Laminated glass has been widely applied to vehicles for windscreens. Optical glass for spectacles has been used since the Middle Ages. The production of lenses has become increasingly proficient, aiding astronomers as well as having other application in medicine and science. Glass is also employed as the aperture cover in many solar energy collectors.

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

## Microscopic structure

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

Glass is an amorphous solid. Although the atomic-scale structure of glass shares characteristics of the structure of a supercooled liquid, glass exhibits all the mechanical properties of a solid. As in other amorphous solids, the atomic structure of a glass lacks the long-range periodicity observed in crystalline solids. Due to chemical bonding constraints, glasses do possess a high degree of short-range order with respect to local atomic polyhedra. The notion that glass flows to an appreciable extent over extended periods of time well below the glass transition temperature is not supported by empirical research or theoretical analysis (see viscosity in solids). Though atomic motion at glass surfaces can be observed, and a viscosity on the order of 1017–1018 Pa s can be measured in glass, such a high value reinforces the fact that glass would not change shape appreciably over even large periods of time.

### Formation from a supercooled liquid

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

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

### Reputed flow

The observation that old windows are sometimes found to be thicker at the bottom than at the top is often offered as supporting evidence for the view that glass flows over a timescale of centuries, the assumption being that the glass has exhibited the liquid property of flowing from one shape to another. This assumption is incorrect, as once solidified, glass stops flowing. The sags and ripples observed in old glass were already there the day it was made; manufacturing processes used in the past produced sheets with imperfect surfaces and non-uniform thickness (the near-perfect float glass used today only became widespread in the 1960s).

A 2017 study computed the rate of flow of the medieval glass used in Westminster Abbey from the year 1268. The study found that the room temperature viscosity of this glass was roughly 1024 Pa·s which is about 1016 times less viscous than a previous estimate made in 1998, which focused on soda-lime silicate glass. Even with this lower viscosity, the study authors calculated that the maximum flow rate of medieval glass is 1nm per billion years, making it impossible to observe in a human timescale.

## Physical properties

### Optical

Glass is in widespread use in optical systems due to its ability to refract, reflect, and transmit light following geometrical optics. The most common and oldest applications of glass in optics are as lenses, windows, mirrors, and prisms. The key optical properties refractive index, dispersion, and transmission, of glass are strongly dependent on chemical composition and, to a lesser degree, its thermal history. Optical glass typically has a refractive index of 1.4 to 2.4, and an Abbe number (which characterises dispersion) of 15 to 100. Refractive index may be modified by high-density (refractive index increases) or low-density (refractive index decreases) additives.

Glass transparency results from the absence of grain boundaries which diffusely scatter light in polycrystalline materials. Semi-opacity due to crystallization may be induced in many glasses by maintaining them for a long period at a temperature just insufficient to cause fusion. In this way, the crystalline, devitrified material, known as Réaumur's glass porcelain is produced. Although generally transparent to visible light, glasses may be opaque to other wavelengths of light. While silicate glasses are generally opaque to infrared wavelengths with a transmission cut-off at 4 μm, heavy-metal fluoride and chalcogenide glasses are transparent to infrared wavelengths of 7 to 18 μm. The addition of metallic oxides results in different coloured glasses as the metallic ions will absorb wavelengths of light corresponding to specific colours.

### Other properties

In the manufacturing process, glasses can be poured, formed, extruded and moulded into forms ranging from flat sheets to highly intricate shapes. The finished product is brittle but can be laminated or tempered to enhance durability.

#### Corrosion resistance

Glass is typically inert, resistant to chemical attack, and can mostly withstand the action of water, making it an ideal material for the manufacture of containers for foodstuffs and most chemicals. Nevertheless, although usually highly resistant to chemical attack, glass will corrode or dissolve under some conditions. The materials that make up a particular glass composition have an effect on how quickly the glass corrodes. Glasses containing a high proportion of alkali or alkaline earth elements are more susceptible to corrosion than other glass compositions.

#### Density

The density of glass varies with chemical composition with values ranging from 2.2 grams per cubic centimetre (2,200 kg/m3) for fused silica to 7.2 grams per cubic centimetre (7,200 kg/m3) for dense flint glass.

#### Strength

Glass is stronger than most metals, with a theoretical tensile strength for pure, flawless glass estimated at 14 to 35 gigapascals (2,000,000 to 5,100,000 psi) due to its ability to undergo reversible compression without fracture. However, the presence of scratches, bubbles, and other microscopic flaws lead to a typical range of 14 to 175 megapascals (2,000 to 25,400 psi) in most commercial glasses. Several processes such as toughening can increase the strength of glass. Carefully drawn flawless glass fibres can be produced with strength of up to 11.5 gigapascals (1,670,000 psi).

## Types

### Silicate

Silicon dioxide (SiO2) is a common fundamental constituent of glass. Fused quartz is a glass made from chemically pure silica. It has very low thermal expansion and excellent resistance to thermal shock, being able to survive immersion in water while red hot, resists high temperatures (1000–1500 °C) and chemical weathering, and is very hard. It is also transparent to a wider spectral range than ordinary glass, extending from the visible further into both the UV and IR ranges, and is sometimes used where transparency to these wavelengths is necessary. Fused quartz is used for high-temperature applications such as furnace tubes, lighting tubes, melting crucibles, etc. However, its high melting temperature (1723 °C) and viscosity make it difficult to work with. Therefore, normally, other substances (fluxes) are added to lower the melting temperature and simplify glass processing.

#### Soda–lime

Sodium carbonate (Na2CO3, "soda") is a common additive and acts to lower the glass-transition temperature. However, sodium silicate is water-soluble, so lime (CaO, calcium oxide, generally obtained from limestone), along with magnesium oxide (MgO), and aluminium oxide (Al2O3), are commonly added to improve chemical durability. Soda–lime glasses (Na2O) + lime (CaO) + magnesia (MgO) + alumina (Al2O3) account for over 75% of manufactured glass, containing about 70 to 74% silica by weight. Soda–lime–silicate glass is transparent, easily formed, and most suitable for window glass and tableware. However, it has a high thermal expansion and poor resistance to heat. Soda–lime glass is typically used for windows, bottles, light bulbs, and jars.

#### Borosilicate

Borosilicate glasses (e.g. Pyrex, Duran) typically contain 5–13% boron trioxide (B2O3). Borosilicate glasses have fairly low coefficients of thermal expansion (7740 Pyrex CTE is 3.25×10−6/°C as compared to about 9×10−6/°C for a typical soda–lime glass). They are, therefore, less subject to stress caused by thermal expansion and thus less vulnerable to cracking from thermal shock. They are commonly used for e.g. labware, household cookware, and sealed beam car head lamps.

#### Lead

The addition of lead(II) oxide into silicate glass lowers melting point and viscosity of the melt. The high density of lead glass (silica + lead oxide (PbO) + potassium oxide (K2O) + soda (Na2O) + zinc oxide (ZnO) + alumina) results in a high electron density, and hence high refractive index, making the look of glassware more brilliant and causing noticeably more specular reflection and increased optical dispersion. Lead glass has a high elasticity, making the glassware more workable and giving rise to a clear "ring" sound when struck. However, lead glass cannot withstand high temperatures well. Lead oxide also facilitates solubility of other metal oxides and is used in coloured glass. The viscosity decrease of lead glass melt is very significant (roughly 100 times in comparison with soda glass); this allows easier removal of bubbles and working at lower temperatures, hence its frequent use as an additive in vitreous enamels and glass solders. The high ionic radius of the Pb2+ ion renders it highly immobile and hinders the movement of other ions; lead glasses therefore have high electrical resistance, about two orders of magnitude higher than soda–lime glass (108.5 vs 106.5 Ω⋅cm, DC at 250 °C).

#### Aluminosilicate

Aluminosilicate glass typically contains 5–10% alumina (Al2O3). Aluminosilicate glass tends to be more difficult to melt and shape compared to borosilicate compositions, but has excellent thermal resistance and durability. Aluminosilicate glass is extensively used for fiberglass, used for making glass-reinforced plastics (boats, fishing rods, etc.), top-of-stove cookware, and halogen bulb glass.

#### Other oxide additives

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

#### Glass-ceramics

Glass-ceramic materials contain both non-crystalline glass and crystalline ceramic phases. They are formed by controlled nucleation and partial crystallisation of a base glass by heat treatment. Crystalline grains are often embedded within a non-crystalline intergranular phase of grain boundaries. Glass-ceramics exhibit advantageous thermal, chemical, biological, and dielectric properties as compared to metals or organic polymers.

The most commercially important property of glass-ceramics is their imperviousness to thermal shock. Thus, glass-ceramics have become extremely useful for countertop cooking and industrial processes. The negative thermal expansion coefficient (CTE) of the crystalline ceramic phase can be balanced with the positive CTE of the glassy phase. At a certain point (\~70% crystalline) the glass-ceramic has a net CTE near zero. This type of glass-ceramic exhibits excellent mechanical properties and can sustain repeated and quick temperature changes up to 1000 °C.

#### Fibreglass

Fibreglass (also called glass fibre reinforced plastic, GRP) is a composite material made by reinforcing a plastic resin with glass fibres. It is made by melting glass and stretching the glass into fibres. These fibres are woven together into a cloth and left to set in a plastic resin. Fibreglass has the properties of being lightweight and corrosion resistant, and is a good insulator enabling its use as building insulation material and for electronic housing for consumer products. Fibreglass was originally used in the United Kingdom and United States during World War II to manufacture radomes. Uses of fibreglass include building and construction materials, boat hulls, car body parts, and aerospace composite materials.

Glass-fibre wool is an excellent thermal and sound insulation material, commonly used in buildings (e.g. attic and cavity wall insulation), and plumbing (e.g. pipe insulation), and soundproofing. It is produced by forcing molten glass through a fine mesh by centripetal force, and breaking the extruded glass fibres into short lengths using a stream of high-velocity air. The fibres are bonded with an adhesive spray and the resulting wool mat is cut and packed in rolls or panels.

### Non-silicate

Besides common silica-based glasses many other inorganic and organic materials may also form glasses, including metals, aluminates, phosphates, borates, chalcogenides, fluorides, germanates (glasses based on GeO2), tellurites (glasses based on TeO2), antimonates (glasses based on Sb2O3), arsenates (glasses based on As2O3), titanates (glasses based on TiO2), tantalates (glasses based on Ta2O5), nitrates, carbonates, plastics, acrylic, and many other substances. Some of these glasses (e.g. Germanium dioxide (GeO2, Germania), in many respects a structural analogue of silica, fluoride, aluminate, phosphate, borate, and chalcogenide glasses) have physico-chemical properties useful for their application in fibre-optic waveguides in communication networks and other specialised technological applications.

Silica-free glasses may often have poor glass forming tendencies. Novel techniques, including containerless processing by aerodynamic levitation (cooling the melt whilst it floats on a gas stream) or splat quenching (pressing the melt between two metal anvils or rollers), may be used to increase cooling rate, or to reduce crystal nucleation triggers.

#### Amorphous metals

In the past, small batches of amorphous metals with high surface area configurations (ribbons, wires, films, etc.) have been produced through the implementation of extremely rapid rates of cooling. Amorphous metal wires have been produced by sputtering molten metal onto a spinning metal disk.

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.

Experimental evidence indicates that the system Al-Fe-Si may undergo a first-order transition to an amorphous form (dubbed "q-glass") on rapid cooling from the melt. Transmission electron microscopy (TEM) images indicate that q-glass nucleates from the melt as discrete particles with a uniform spherical growth in all directions. While x-ray diffraction reveals the isotropic nature of q-glass, a nucleation barrier exists implying an interfacial discontinuity (or internal surface) between the glass and melt phases.

#### Polymers

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

### Molecular liquids and molten salts

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

## Production

Following the glass batch preparation and mixing, the raw materials are transported to the furnace. Soda–lime glass for mass production is melted in glass melting furnaces. 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.

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

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

### Colour

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

## Uses

### Architecture and windows

Soda–lime sheet glass is typically used as transparent glazing material, typically as windows in external walls of buildings. Float or rolled sheet glass products is cut to size either by scoring and snapping the material, laser cutting, water jets, or diamond bladed saw. The glass may be thermally or chemically tempered (strengthened) for safety and bent or curved during heating. Surface coatings may be added for specific functions such as scratch resistance, blocking specific wavelengths of light (e.g. infrared or ultraviolet), dirt-repellence (e.g. self-cleaning glass), or switchable electrochromic coatings.

Structural glazing systems represent one of the most significant architectural innovations of modern times, where glass buildings now often dominate skylines of many modern cities. These systems use stainless steel fittings countersunk into recesses in the corners of the glass panels allowing strengthened panes to appear unsupported creating a flush exterior. Structural glazing systems have their roots in iron and glass conservatories of the nineteenth century

### Tableware

Glass is an essential component of tableware and is typically used for water, beer and wine drinking glasses. Wine glasses are typically stemware, i.e. goblets formed from a bowl, stem, and foot. Crystal or Lead crystal glass may be cut and polished to produce decorative drinking glasses with gleaming facets. Other uses of glass in tableware include decanters, jugs, plates, and bowls.

### Packaging

The inert and impermeable nature of glass makes it a stable and widely used material for food and drink packaging as glass bottles and jars. Most container glass is soda–lime glass, produced by blowing and pressing techniques. Container glass has a lower magnesium oxide and sodium oxide content than flat glass, and a higher silica, calcium oxide, and aluminum oxide content. Its higher content of water-insoluble oxides imparts slightly higher chemical durability against water, which is advantageous for storing beverages and food. Glass packaging is sustainable, readily recycled, reusable and refillable.

For electronics applications, glass can be used as a substrate in the manufacture of integrated passive devices, thin-film bulk acoustic resonators, and as a hermetic sealing material in device packaging, including very thin solely glass based encapsulation of integrated circuits and other semiconductors in high manufacturing volumes.

### Laboratories

Glass is an important material in scientific laboratories for the manufacture of experimental apparatus because it is relatively cheap, readily formed into required shapes for experiment, easy to keep clean, can withstand heat and cold treatment, is generally non-reactive with many reagents, and its transparency allows for the observation of chemical reactions and processes. Laboratory glassware applications include flasks, petri dishes, test tubes, pipettes, graduated cylinders, glass lined metallic containers for chemical processing, fractionation columns, glass pipes, Schlenk lines, gauges, and thermometers. Although most standard laboratory glassware has been mass-produced since the 1920s, scientists still employ skilled glassblowers to manufacture bespoke glass apparatus for their experimental requirements.

### Optics

Glass is a ubiquitous material in optics by virtue of its ability to refract, reflect, and transmit light. These and other optical properties can be controlled by varying chemical compositions, thermal treatment, and manufacturing techniques. The many applications of glass in optics includes glasses for eyesight correction, imaging optics (e.g. lenses and mirrors in telescopes, microscopes, and cameras), fibre optics in telecommunications technology, and integrated optics. Microlenses and gradient-index optics (where the refractive index is non-uniform) find application in e.g. reading optical discs, laser printers, photocopiers, and laser diodes.

### Art

Glass as art dates to least 1300 BC shown as an example of natural glass found in Tutankhamun's pectoral, which also contained vitreous enamel, that is to say, melted coloured glass used on a metal backing. Enamelled glass, the decoration of glass vessels with coloured glass paints, has existed since 1300 BC, and was prominent in the early 20th century with Art Nouveau glass and that of the House of Fabergé in St. Petersburg, Russia. Both techniques were used in stained glass, which reached its height roughly from 1000 to 1550, before a revival in the 19th century.

The 19th century saw a revival in ancient glassmaking techniques including cameo glass, achieved for the first time since the Roman Empire, initially mostly 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 in the first French wave of the movement, producing coloured vases and similar pieces, often in cameo glass or in lustre glass techniques.

Louis Comfort Tiffany in America specialised in stained glass, both secular and religious, in panels and his famous lamps. The early 20th-century saw the large-scale factory production of glass art by firms such as Waterford and Lalique. Small studios may hand-produce glass artworks. Techniques for producing glass art include blowing, kiln-casting, fusing, slumping, pâte de verre, flame-working, hot-sculpting and cold-working. Cold work includes traditional stained glass work and other methods of shaping glass at room temperature. Objects made out of glass include vessels, paperweights, marbles, beads, sculptures and installation art.

## See also

- Fire glass
- Flexible glass
- Kimberley points
- Prince Rupert's drop
- Smart glass

Transparent non-crystalline solid material


Forensic firearm examination

Forensic firearm examination is the forensic process of examining the characteristics of firearms or bullets left behind at a crime scene. Specialists in this field try to link bullets to weapons and weapons to individuals. They can raise and record obliterated serial numbers in an attempt to find the registered owner of a weapon and look for fingerprints on a weapon and cartridges.

By examining unique striations impressed into a bullet from the barrel of a gun, expended ammunition can be linked back to a specific weapon. These striations are due to the rifling inside the barrels of firearms. Rifling spins the bullet when it is fired out of the barrel to improve precision. Although bullet striations are individualized unique evidence, microscopic striations in the barrel of the weapon are subject to change slightly, after each round that is fired. For this reason, forensic ballistics examiners may not fire more than five shots from a weapon found at a scene. Known exemplars taken from a seized weapon can be compared to samples recovered from a scene using a comparison microscope as well as newer 3-D imaging technology. Striation images can also be uploaded to national databases. Furthermore, the markings can be compared to other images in an attempt to link one weapon to multiple crime scenes.

Like all forensic specialties, forensic firearm examiners are subject to being called to testify in court as expert witnesses. However, the reliability of some techniques of forensic firearm examination have been criticized.

## History

The ability to compare ammunition is a direct result of the invention of rifling around the turn of the 16th century. By forcing the bullet to spin as it travels down the barrel of the weapon the precision is greatly increased. At the same time, the rifling leaves marks on the bullet that are indicative of that particular barrel. Prior to mass production of firearms, each barrel and bullet mold was hand made by gunsmiths making them unique. The first successful documented case of forensic firearm examination occurred in 1835 when a member of the Bow Street Runners in London matched a recovered bullet from a murder victim to a specific mold in a suspect's home confirming that he made the bullet; this gave further evidence that the bullet maker was the perpetrator and he was convicted. As manufacturing and automation replaced hand tools, the ability to compare bullets became impossible due to the standardization of molds within a specific company. However, experts in the field postulated that there were microscopic differences on each barrel left during the manufacturing process. These differences were a result of wear on the machines and since each new weapon caused a tiny amount of wear, each barrel would be slightly different from every other barrel produced by that company. Also, each bullet fired from a specific barrel would be printed with the same marks, allowing investigators to identify the weapon that fired a specific bullet.

One of the first uses of this knowledge was in 1915 to exonerate Charles Stielow of the murder of his neighbors. Stielow was sentenced to death and appealed to Charles S. Whitman, the Governor of New York, who was not convinced by the evidence used to convict Stielow. Whitman halted the execution until an inquiry could be conducted and after further examination it was shown that Stielow's firearm could not have fired the bullets recovered from the victims. The invention of the comparison microscope by Calvin Goddard and Phillip O. Gravelle in 1925 modernized the forensic examination of firearms. Simultaneous comparison of two different objects at the same time allowed to closely examine striations for matches and therefore make a more definitive statement as to whether or not they matched.

One of the first true tests of this new technology was in the aftermath of the Saint Valentine's Day Massacre in 1929. During the Prohibition Era, competing gang members were fighting over bootlegging operations within the city of Chicago. Members of the Chicago Outfit and the Egan's Rats led by Al Capone attempted to remove all competition from Chicago by eliminating the North Side Gang leader Bugs Moran. The massacre missed Moran, who was not present, but killed seven members of the North Side Gang. The murderers attempted to cover up their crime by posing as police officers, even dressing in police uniforms. Witnesses saw two "officers" leaving the scene, which implicated the Chicago police department as the perpetrators of the massacre. High levels of police corruption during that time period made it seem likely that the police department committed the killings. The investigation stalled until December 1929 when Fred Burke, a member of the Egan's Rats, shot and killed a police officer in St. Joseph, Michigan. Officers searching for Burke were led to a home in nearby Stevensville. While Burke was not there, inside officers found an arsenal of weapons including two Thompson submachine guns. The Chicago police department was contacted and the weapons were brought back to Chicago for testing. Goddard was asked to compare the weapons to collected evidence found at the massacre using his new "ballistic-forensics" technique. After test firing the guns, Goddard proved that the weapons were those used to kill the members of the North Side Gang, absolving the Chicago police department of all involvement. The successful use of Goddard's technique resulted in the solidification of his place as the father of forensic firearm examination.

## Examination of the firearm

Any firearm collected during the course of an investigation could yield viable evidence if examined. For forensic firearm examination specific evidence that can be recovered include weapon serial numbers and potentially fingerprints left on the weapon's surface.

### Fingerprint recovery

Fingerprint recovery from the surface of firearms is done with cyanoacrylate (more commonly known as superglue) fuming. Firearms are placed in a specially designed fume hood designed to evenly distribute fumes instead of removing them. Liquid superglue is placed in a container and heated until it is in a gaseous state. The circulating fumes adhere to the oils left behind by the fingerprint, turning the print white. The resulting white print can be enhanced with fingerprint powder to increase the contrast of the white print against the weapon's finish. While using the fuming technique on recovered guns is commonplace, the recovery of fingerprints from the surfaces of a firearm is challenging due to the textured grip and the general condition of recovered weapons. If fingerprints are recovered, they can be processed through fingerprint databases such as the Integrated Automated Fingerprint Identification System (IAFIS). Various parts of the recovered weapon can also be tested for touch DNA left by whoever handled it. However, the low levels of DNA that can be recovered presents numerous issues such as contamination and analysis anomalies such as allele drop-out and drop-in.

### Serial number recovery

Serial number examinations are a form of tool mark analysis. Serial numbers became commonplace after the United States passed the Gun Control Act of 1968. This law mandated that all guns manufactured in or imported into the country have a serial number. Prior to 1968, many firearms either did not have a serial number or the serial numbers were not unique and were reused by a manufacturer on multiple firearms. If a recovered weapon has had the serial numbers altered or destroyed, examiners can attempt to recover the original numbers. The two main methods for the restoration of serial numbers are magnetic particle inspection and chemical restoration. It is recommended that magnetic particle inspection be performed first due to the nondestructive nature of the method. If magnetic particle inspection fails, chemical restoration is the next step in the forensic analysis.

If the serial number is successfully restored it can be used to help investigators track the weapon's history, as well as potentially determine who owns the weapon. Firearm databases such as the National Crime Information Center of the United States and INTERPOL's Firearm Reference Table can be used by investigators to track weapons that have been lost, stolen, or used previously in other crimes.

#### Magnetic particle inspection

Originally developed as a method to detect flaws or irregularities in magnetic materials, magnetic particle inspection can be used on firearms to visualize the serial number underneath the obliterated area. When performing this technique, examiners place the weapon in a magnetic field. The irregularities in the metal, in this case the serial number, cause the field to deform. When a solution of ferrous particles is added to the weapon's magnetized surface they will be attracted to the area where the magnetic field has deformed and will build up in the area. If fluorescent particles are added to the ferrous solution, ultraviolet light can be used to make it easier to visualize any recovered serial number.

#### Chemical restoration

Chemical restoration is a type of chemical milling. Typically, chemical milling is used to slowly remove material to create a desired shape. In serial number restoration, small amounts of metal are removed until variations in the metal corresponding to the serial number are visible. This is possible because stamping the numbers distorts the grain boundary structure underneath the surface of the metal. However, chemical restoration is limited to that depth and is only successful when the obliteration of the serial number is superficial. Examiners performing a restoration first sand the area where the serial number used to be. This removes any debris from the area left when the serial number was obliterated. The examiner then chooses a chemical, usually an acid, that will be used to slowly bring the number back to the surface. The type of chemical that is used depends on the material the weapon is made of. These acids can range from Fry's Reagent for a magnetic metal, which is a mixture of hydrochloric acid, cupric chloride, and distilled water, to an acidic ferric chloride solution for a non-magnetic, non-aluminum material.

## Examination of cartridges

Spent cartridges found at a scene can be examined for physical evidence such as fingerprints or compared to samples that match them to a weapon. The examination of the cartridge relies on the unique tool marks left by the various parts of the weapon including the firing pin and the ejector in semi and fully automatic firearms. These markings can be compared and matched to known exemplars fired from the same weapon using the same parts. The examination of the marks left on the cartridge is done using a comparison microscope. Examiners view the questioned cartridge and the known exemplar simultaneously, looking for similar microscopic marks left during the firing process.

Cartridges are also routinely examined for fingerprints as the act of loading the ammunition into the magazine, or chamber, leaves recoverable impressions. These fingerprints can survive the firing processes and, while a rare occurrence, fingerprints have been obtained from cartridges recovered from the scene. Cartridges are subjected to cyanoacrylate fuming and examined for any usable prints. Usable prints are photographed and can be uploaded to fingerprint databases such as IAFIS for comparison with known exemplars. Cartridges can also be swabbed for trace DNA left by the individual who loaded the magazine. The extremely low levels of recoverable DNA present the same issues as swabbing a firearm for DNA.

Advancements in microscopic stamping have led to a push for the inclusion of firing pin microstamping. The microstamp is etched onto the firing pin and is transferred to the cartridge during the firing process. Each firing pin would have a unique serial number allowing investigators to trace casings found at a crime scene to a known firearm. The practice is not in use as of 2023, although California has enacted legislation that requires microstamping on all newly sold firearms. The law, and microstamping in general, has received significant opposition from gun manufacturers due the technology being unreliable, and not proven to aid in preventing or solving crimes.

## Examination of bullets

### Class characteristics

Preliminary examination of the bullet can exclude a large number of weapons by examining the general characteristics of a recovered bullet. By determining general aspects of the fired ammunition, a number of weapons can be immediately excluded as being incapable of firing that type of bullet. The make and model of the weapon can also be inferred from the combination of different class characteristics that are common to specific manufactures. The three main class characteristics of all bullets are the lands and grooves, the caliber of the bullet, and the rifling twist. All three can be tied directly to the type of barrel that was used to fire the bullet. The lands and grooves of barrel are the bumps and valleys created when the rifling is created. The caliber is the diameter of the barrel. The twist is the direction of the striations left by the barrel's rifling, clockwise (right-handed) or counterclockwise (left-handed). Most barrels will have a right-handed twist with the exception of weapons created by the Colt's Manufacturing Company which uses left-handed twists. Weapon barrels that match the class characteristics of recovered bullets can be examined further for individual characteristics to determine if the bullet came from that particular weapon.

### Individual characteristics

In order to compare individual striations, examiners must obtain a known sample using the seized weapon. For slower-traveling bullets, such as pistols or revolvers, known bullet exemplars are created by firing the weapon into a water tank. The spent bullet can be recovered, intact, as the water slows down the bullet before it can reach the tank walls. For faster traveling bullets, such as those fired from high-powered rifles and military style weapons, water tanks cannot be used as the tank will not provide enough stopping power for the projectiles. To examine these weapons, investigators must fire them at a target at a controlled range with enough backing to stop the bullet and collect the spent round after it has been fired.

Once a known exemplar is produced, the evidence sample can be compared to the known by examining both at the same time with a comparison microscope. Striations that line up are examined more closely, looking for multiple consecutive matches. There is no set number of consecutive matches that equates to a match declaration, and examiners are trained to use the phrase "sufficient agreement" when testifying. The degree to which an examiner can make that determination is based on their training and expertise. All findings by examiners are subject to questioning by both sides, prosecution and defense, during testimony in court.

## Striation databasing

Bullets and casings found at a scene require a known example to compare to in order to match them to a weapon. Without a weapon, the striation pattern can be uploaded to a database such as the National Integrated Ballistic Identification Network (NIBIN) maintained by the ATF or the United Kingdom's National Ballistics Intelligence Service (NABIS). Information uploaded to these databases can be used to track gun crimes and to link crimes together. Maintainers of these databases recommend that every recovered firearm be test fired and the resulting known exemplar be uploaded into the database.

In the 1990s, there were two databases that were formed for storage of pictures of shell casings and bullets in gun crimes. The first was the Drugfire system which was used by the FBI. The second, the IBIS (Integrated Ballistic Identification System) was created by Forensic Technology, Inc. and eventually bought by the Alcohol Tobacco and Firearms (ATF) in 1993. The FBI and ATF realized that their systems would not work together, and they needed to find a way to share information between them. The NIBIN board was created in 1997, in hopes of creating one imaging system.  A year after the creation of the NIBIN board, both the ATF and FBI decided to put their resources together toward one of the systems, and created the National Integrated Ballistics Information Network, with IBIS as the system.

## Criticisms

Firearm examiners have attempted to determine the shooter's position by the location of spent bullet casings. The use of ejection pattern studies were originally part of incident reconstruction and methods for determining shooter location continue to be explained in major crime scene examination books. However, the validity of ejection pattern analysis has been brought into question by multiple studies that look at the reproducibility and end determination of shooter position by qualified examiners. Studies have shown that over 25% of spent casings land somewhere other than to the right and rear of the shooter. This is the most commonly accepted location for where spent cartridge casings should fall, and the large percentage of casings that end up somewhere else raises concerns for the validity of the examination technique. Investigators should only present a location gained from an ejection pattern study as a tentative estimate when using the information in a courtroom setting.

Prior to September 2005, comparative bullet-lead analysis was performed on bullets found at a scene that were too destroyed for striation comparison. The technique would attempt to determine the unique elemental breakdown of the bullet and compare it to seized bullets possessed by a suspect. Review of the method found that the breakdown of elements found in bullets could be significantly different enough to potentially allow for two bullets from separate sources to be correlated to each other. However, there are not enough differences to definitely match a bullet from a crime scene to one taken from a suspect's possession. An additional report in 2004 from the National Academy of Sciences (NAS) found that the testimony given regarding comparative bullet-lead analysis was overstated and potentially "misleading under the federal rules of evidence". In 2005, the Federal Bureau of Investigation indicated that they would no longer be performing comparative bullet-lead analysis.

Further criticism came from the 2009 NAS report on the current state of various forensic fields in the United States. The report's section on firearm examination focused on the lack of defined requirements that are necessary in order to determine "matches" between known and unknown striations. The NAS stated that, "sufficient studies have not been done to understand the reliability and repeatability of the methods." Without defined procedures on what is and what isn't considered "sufficient agreement" the report states that forensic firearm examination contains fundamental problems that need to be addressed by the forensic community through a set of repeatable scientific studies that outline standard operating procedures that should be adopted by all firearm examiners. Another report issued in 2016 by the United States President's Council of Advisors on Science and Technology confirmed the NAS's findings, finding only one appropriately designed study that examined the rate of false positives and reliability amongst firearm examiners.

In 2020 Itiel E. Dror and Nicholas Scurich looked at the validity of ballistic forensic experts when attempting to make an identification of a shell or bullet. They found that while some experts would come to the conclusion that the bullets were a definite match, another expert looking at the same evidence would determine it inconclusive. Dror and Scurich argue an "inconclusive" determination affects the error rate for the study, and provides very little confidence in the overall findings of the scientists. According to Dror and Scurich, the error rate, which was zero to one percent, could be higher. Their reasoning behind this is that if an "answer" was marked as inconclusive, it must count as a correct answer which decreases the error rate making it lower than it probably should be.They wondered how different the error rate would be if inconclusive was not an option. In addition, Dror and Scruich noted that the scientists seemed to come up with a more conclusive decision on the evidence if there was the added part of a human life hanging in the balance. In 2021 Alex Biederman and Kyriakos N. Kotsoglou responded to the Dror and Scurich paper and raised issues. Some of the issues raised by Biederman and Kotsoglou included: a paradox in which examiners' results agreed with ground truth but would be considered "error" via Dror and Scurich's proposals. Biederman and Kotsoglou also pointed out that Dror and Scurich's proposals would set false incentives where examiners would be directed to be "diving what the mythical forensic wisdom of the consensus opinion might (and hence enshrine the false belief in the existence of such wisdom), be rather than the ground truth". Biederman and Kotsoglou concluded "In all, our analysis does not leave much intact from recent attempts to label 'inconclusives as errors."

## See also

- Edward O. Heinrich
- Ballistics
- Crime reconstruction
- Evidence packaging

Analysis of firearms and bullets for presentation as legal evidence


HMS Prince of Wales (53)

HMS Prince of Wales was a King George V-class battleship of the Royal Navy that was built at the Cammell Laird shipyard in Birkenhead. She had an extensive battle history, first seeing action in August 1940 while still being outfitted in her drydock when she was attacked and damaged by German aircraft. In her brief career, she was involved in several key actions of the Second World War, including the May 1941 Battle of the Denmark Strait where she scored three hits on the German battleship Bismarck, forcing Bismarck to abandon her raiding mission and head to port for repairs. Prince of Wales later escorted one of the Malta convoys in the Mediterranean, during which she was attacked by Italian aircraft. In her final action, she attempted to intercept Japanese troop convoys off the coast of Malaya as part of Force Z when she was sunk by Japanese aircraft on 10 December 1941, two days after the attack on Pearl Harbor.

She was sunk alongside her consort, the battlecruiser HMS Repulse, in an attack by 85 Mitsubishi G3M and G4M bombers of the Japanese navy air service. HMS Prince of Wales and Repulse became the first capital ships to be sunk solely by air power on the open sea, a harbinger of the diminishing role this class of ships was subsequently to play in naval warfare. The wreck of Prince of Wales lies upside down in 223 feet (68 m) of water, near Kuantan, in the South China Sea.

In the 21st century, her wreck was illegally salvaged by scrap metal dealers.

## Construction

In the aftermath of the First World War, the Washington Naval Treaty was drawn up in 1922 in an effort to stop an arms race developing between Britain, Japan, France, Italy and the United States. This treaty limited the number of ships each nation was allowed to build and capped the tonnage of all capital ships at 35,000 tons. These restrictions were extended in 1930 through the Treaty of London, however, by the mid-1930s Japan and Italy had withdrawn from both of these treaties, and the British became concerned about a lack of modern battleships within their navy. As a result, the Admiralty ordered the construction of a new battleship class: the King George V class. Due to the provisions of both the Washington Naval Treaty and the Treaty of London, both of which were still in effect when the King George Vs were being designed, the main armament of the class was limited to the 14-inch (356 mm) guns prescribed under these instruments. They were the only battleships built at that time to adhere to the treaty, and even though it soon became apparent to the British that the other signatories to the treaty were ignoring its requirements, it was too late to change the design of the class before they were laid down in 1937.

Prince of Wales was originally to be named King Edward VIII but upon the abdication of Edward VIII the ship was renamed even before she had been laid down. This occurred at Cammell Laird's shipyard in Birkenhead on 1 January 1937, although it was not until 3 May 1939 that she was launched. She was still fitting out when war was declared in September, causing her construction schedule, and that of her sister, King George V, to be accelerated. Nevertheless, the late delivery of gun mountings caused delays in her outfitting.

In early August 1940, while she was still being outfitted and was in a semi-complete state, Prince of Wales was attacked by German aircraft. One bomb fell between the ship and a wet basin wall, narrowly missing a 100-ton dockside crane, and exploded underwater below the bilge keel. The explosion took place about six feet from the ship's port side in the vicinity of the aft group of 5.25-inch guns. Buckling of the shell plating took place over a distance of 20 to 30 feet (9.1 m), rivets were sprung and considerable flooding took place in the port outboard compartments in the area of damage, causing a ten-degree port list. The flooding was severe, because final compartment air tests had not yet been made and the ship did not have her pumping system in operation.

The water was pumped out through the joint efforts of a local fire company and the shipyard, and Prince of Wales was later dry-docked for permanent repairs. This damage and the problem with the delivery of her main guns and turrets delayed her completion. As the war progressed there was an urgent need for capital ships, and so her completion was advanced by postponing compartment air tests, ventilation tests and thorough testing of her bilge, ballast and fuel-oil systems.

## Description

Prince of Wales displaced 36,727 long tons (37,300 t) as built and 43,786 long tons (44,500 t) fully loaded. The ship had an overall length of 745 feet (227.1 m), a beam of 103 feet (31.4 m) and a draught of 29 feet (8.8 m). Her designed metacentric height was 6 feet 1 inch (1.85 m) at normal load and 8 feet 1 inch (2.46 m) at deep load.

She was powered by Parsons geared steam turbines, driving four propeller shafts. Steam was provided by eight Admiralty boilers which normally delivered 100,000 shaft horsepower (75,000 kW), but could deliver 110,000 shp (82,000 kW) with forced draft. This gave Prince of Wales a top speed of 28 knots (52 km/h; 32 mph). The ship carried 3,542 long tons (3,600 t) of fuel oil. She also carried 180 long tons (200 t) of diesel oil, 256 long tons (300 t) of reserve feed water and 444 long tons (500 t) of freshwater. During full-power trials on 31 March 1941, Prince of Wales at 42,100 tons displacement achieved 28 knots with 111,600 shp at 228 rpm and a specific fuel consumption of 0.73 lb per shp. Prince of Wales had a range of 3,100 nautical miles (5,700 km; 3,600 mi) at 27 knots (50 km/h; 31 mph).

### Armament

Prince of Wales mounted 10 BL 14-inch (356 mm) Mk VII guns. The 14-inch guns were mounted in one Mark II twin turret forward and two Mark III quadruple turrets, one forward and one aft. The guns could be elevated 40 degrees and depressed 3 degrees. Training arcs were: turret "A", 286 degrees; turret "B", 270 degrees; turret "Y", 270 degrees. Training and elevating was done by hydraulic drives, with rates of two and eight degrees per second, respectively. A full gun broadside weighed 15,950 pounds (7,230 kg), and a salvo could be fired every 40 seconds. The secondary armament consisted of 16 QF 5.25-inch (133 mm) Mk I guns which were mounted in eight twin mounts, weighing 81 tons each. The maximum range of the Mk I guns was 24,070 yards (22,009.6 m) at a 45-degree elevation, the anti-aircraft ceiling was 49,000 feet (14,935.2 m). The guns could be elevated to 70 degrees and depressed to 5 degrees. The normal rate of fire was ten to twelve rounds per minute, but in practice, the guns could only fire seven to eight rounds per minute. Along with her main and secondary batteries, Prince of Wales carried 32 QF 2 pdr (1.575-inch, 40.0 mm) Mk.VIII "pom-pom" anti-aircraft guns. She also carried 80 UP projectors, short-range rocket-firing anti-aircraft weapons used in the early days of the Second World War by the Royal Navy.

## Operational service

### Action with Bismarck

On 22 May 1941, Prince of Wales, the battlecruiser Hood and six destroyers were ordered to take station south of Iceland and intercept the German battleship Bismarck if she attempted to break out into the Atlantic. Captain John Leach knew that main-battery breakdowns were likely to occur, since Vickers-Armstrongs technicians had already corrected some that took place during training exercises in Scapa Flow. These technicians were personally requested by the captain to remain aboard. They did so and played an important role in the resulting action.

The next day Bismarck, in company with the heavy cruiser Prinz Eugen, was reported heading south-westward in the Denmark Strait. At 20:00 Vice-Admiral Lancelot Holland, in his flagship Hood, ordered the force to steam at 27 knots (50 km/h), which it did most of the night. His battle plan called for Prince of Wales and Hood to concentrate on Bismarck, while the cruisers Norfolk and Suffolk would handle Prinz Eugen. However the two cruisers were not informed of this plan because of strict radio silence. At 02:00, on 24 May, the destroyers were sent as a screen to search for the German ships to the north, and at 02:47 Hood and Prince of Wales increased speed to 28 knots (52 km/h) and changed course slightly to obtain a better target angle on the German ships. The weather improved, with 10-mile (16 km) visibility, and crews were at action stations by 05:10.

At 05:37 an enemy contact report was made, and course was changed to starboard to close range. Neither ship was in good fighting trim. Hood, designed twenty-five years earlier, lacked adequate decking armour and would have to close the range quickly, as she would become progressively less vulnerable to plunging shellfire at shorter ranges. She had completed an overhaul in March and her crew had not been adequately retrained. Prince of Wales, with thicker armour, was less vulnerable to 15-inch shells at ranges greater than 17,000 feet (5,200 m), but her crew had also not been trained to battle efficiency. The British ships made their last course change at 05:49, but they had made their approach too fine (the German ships were only 30 degrees on the starboard bow) and their aft turrets could not fire. Prinz Eugen, with Bismarck astern, had Prince of Wales and Hood slightly forward of the beam, and both ships could deliver full broadsides.

At 05:53, despite seas breaking over the bows, Prince of Wales opened fire on Bismarck at 26,500 yards (24,200 m). There was some confusion among the British as to which ship was Bismarck and thirty seconds earlier Hood had mistakenly opened fire on Prinz Eugen as the German ships had similar profiles. Hood's first salvo straddled the enemy ship, but Prinz Eugen, in less than three minutes, scored 8-inch-shell hits on Hood. The first shots by Prince of Wales – two three-gun salvoes at ten-second intervals – were 1,000 yards over. The turret rangefinders on Prince of Wales could not be used because of spray over the bow and fire was instead directed from the 15-foot (4.6 m) rangefinders in the control tower.

The sixth, ninth and thirteenth salvos were straddles and two hits were made on Bismarck. One shell holed her bow and caused Bismarck to lose 1,000 tons of fuel oil, mostly to salt-water contamination. The other fell short, and entered Bismarck below her side armour belt, the shell exploded and flooded the auxiliary boiler machinery room and forced the shutdown of two boilers due to a slow leak in the boiler room immediately aft. The loss of fuel and boiler power were decisive factors in the Bismarck's decision to return to port. In Prince of Wales, "A1" gun ceased fire after the first salvo due to a defect. Sporadic breakdowns occurred until the decision to turn away was made, and during the turn "Y" turret jammed.

Both German ships initially concentrated their fire on Hood and destroyed her with salvoes of 8- and 15-inch shells. An 8-inch shell hit the boat deck and struck a ready service locker for ammunition, and a fire blazed high above the first superstructure deck. At 05:58 at a range of 16,500 yards (15,100 m), the force commander ordered a turn of 20 degrees to port to open the range and bring the full battery of the British ships to bear on Bismarck. As the turn began, Bismarck straddled Hood with her third and fourth four-gun salvoes and at 06:01 the fifth salvo hit her, causing a large explosion. Flames shot up near Hood's masts, then an orange-coloured fireball and an enormous smoke cloud obliterated the ship. On Prince of Wales, it seemed that Hood collapsed amidships, and the bow and stern could be seen rising as she rapidly settled. Prince of Wales made a sharp starboard turn to avoid hitting the debris and in doing so further closed the range between her and the German ships. In the four-minute action, Hood, the largest battlecruiser in the world, had been sunk. 1,419 officers and men were killed. Only three men survived.

Prince of Wales fired unopposed until she began a port turn at 05:57, when Prinz Eugen took her under fire. After Hood exploded at 06:01, the Germans opened intense and accurate fire on Prince of Wales, with 15-inch, 8-inch and 5.9-inch guns. A heavy hit was sustained below the waterline as Prince of Wales manoeuvred through the wreckage of Hood. At 06:02, a 15-inch shell struck the starboard side of the compass platform and killed the majority of the personnel there. The navigating officer was wounded, but Captain Leach was unhurt. Casualties were caused by the fragments from the shell's ballistic cap and the material it dislodged in its diagonal path through the compass platform. A 15-inch diving shell penetrated the ship's side below the armour belt amidships, failed to explode and came to rest in the wing compartments on the starboard side of the after boiler rooms. The shell was discovered and defused when the ship was docked at Rosyth.

At 06:05 Captain Leach decided to disengage and laid down a heavy smokescreen to cover Prince of Wales's escape. Leach then radioed Norfolk that Hood had been sunk and went to join Suffolk 15 to 17 miles (24 to 27 km) astern of Bismarck. The British ships continued to chase Bismarck until 18:16 when Suffolk sighted the German battleship at 22,000 yards (20,000 m). Prince of Wales then opened fire on Bismarck at an extreme range of 30,300 yards (27,700 m). All 12 salvos missed. At 01:00 on 25 May Prince of Wales again regained contact and opened fire at a radar range of 20,000 yards (18,000 m), after observers believed that she had scored a hit on Bismarck, Prince of Wales's "A" turret temporarily jammed, leaving her with only six operational guns. After losing Bismarck owing to poor visibility, and after searching for 12 hours, Prince of Wales headed for Iceland. Thirteen of her crew had been killed, and nine wounded.

On Friday 6 June, while in dry dock, a hole was found just above the starboard bilge keel. After the inner space had been pumped out, an unexploded shell from Bismarck was found nose forward, with its fuse, but without a ballistic cap. The shell was removed by the Bomb Disposal Officer from HMS Cochrane

### Atlantic Charter meeting

After repairs at Rosyth, Prince of Wales took Prime Minister Winston Churchill across the Atlantic for a secret conference with US President Franklin D. Roosevelt. On 5 August Roosevelt boarded the cruiser USS Augusta from the presidential yacht Potomac. Augusta proceeded from Massachusetts to Placentia Bay and Argentia in Newfoundland with the cruiser USS Tuscaloosa and five destroyers, arriving on 7 August while Potomac played a decoy role by continuing to cruise New England waters as if the president were still on board. On 9 August, Churchill arrived in the bay aboard Prince of Wales, escorted by the destroyers HMS Ripley, and . At Placentia Bay, Newfoundland, Roosevelt transferred to the destroyer USS McDougal to meet Churchill on board Prince of Wales. The conference continued from 10 to 12 August aboard Augusta and, at the end of the conference, the Atlantic Charter was proclaimed. Prince of Wales arrived back at Scapa Flow on 18 August.

### Mediterranean duty

In September 1941, Prince of Wales was assigned to Force H, in the Mediterranean. On 24 September Prince of Wales formed part of Group II, led by Vice-Admiral Alban Curteis and consisting of the battleships Prince of Wales and Rodney, the cruisers Kenya, Edinburgh, Sheffield and Euryalus, and twelve destroyers. The force provided an escort for Operation Halberd, a supply convoy from Gibraltar to Malta. On 27 September the convoy was attacked by Italian aircraft, with Prince of Wales shooting down several with her 5.25-inch (133 mm) guns. Later that day there were reports that units of the Italian Fleet were approaching. Prince of Wales, the battleship Rodney and the aircraft carrier Ark Royal were despatched to intercept, but the search proved fruitless. The convoy arrived in Malta without further incident, and Prince of Wales returned to Gibraltar, before sailing on to Scapa Flow, arriving there on 6 October.

### Far East

On 25 October Prince of Wales and a destroyer escort left home waters bound for Singapore, there to rendezvous with the battlecruiser Repulse and the aircraft carrier Indomitable. Indomitable however ran aground off Jamaica a few days later and was unable to proceed. Calling at Freetown and Cape Town South Africa to refuel and generate publicity, Prince of Wales also stopped in Mauritius and the Maldive Islands. Prince of Wales reached Colombo, Ceylon, on 28 November, joining Repulse the next day. On 2 December the fleet docked in Singapore. Prince of Wales then became the flagship of Force Z, under the command of Admiral Sir Tom Phillips. Admiral of the Home Fleet Sir John Tovey was opposed to sending any of the new King George V battleships as he believed that they were not suited to operating in tropical climates.

Japanese troop-convoys were first sighted on 6 December. Two days later, Japanese aircraft raided Singapore; although the Prince of Wales's anti-aircraft batteries opened fire, they scored no hits and had no effect on the Japanese aircraft. A signal was received from the Admiralty in London ordering the British squadron to commence hostilities, and that evening, confident that a protective air umbrella would be provided by the RAF presence in the region, Admiral Phillips set sail. Force Z at this time comprised the battleship Prince of Wales, the battlecruiser Repulse, and the destroyers Electra, Express, Tenedos and .

The object of the sortie was to attack Japanese transports at Kota Bharu, but in the afternoon of 9 December the Japanese submarine I-65 spotted the British ships, and in the evening they were detected by Japanese aerial reconnaissance. By this time it had been made clear that no RAF fighter support would be forthcoming. At midnight a signal was received that Japanese forces were landing at Kuantan in Malaya. Force Z was diverted to investigate. At 02:11 on 10 December the force was again sighted by a Japanese submarine and at 08:00 arrived off Kuantan, only to discover that the reported landings were a diversion.

At 11:00 that morning the first Japanese air attack began. Eight Type 96 "Nell" bombers dropped their bombs close to Repulse, one passing through the hangar roof and exploding on the 1-inch plating of the main deck below. The second attack force, comprising seventeen "Nells" armed with torpedoes, arrived at 11:30, divided into two attack formations. Despite reports to the contrary, Prince of Wales was struck by only one torpedo. Meanwhile, Repulse avoided the seven torpedoes aimed at her, as well as bombs dropped by six other "Nells" a few minutes later.

The torpedo struck Prince of Wales on the port side aft, abaft "Y" Turret, wrecking the outer propeller shaft on that side and destroying bulkheads to one degree or another along the shaft all the way to B Engine Room. This caused rapid uncontrollable flooding and put the entire electrical system in the after part of the ship out of action. Lacking effective damage control, she soon took on a heavy list.

A third torpedo attack developed against Repulse and once again she avoided taking any hits.

A fourth attack, conducted by torpedo-carrying Type 1 "Bettys", developed. This one scored hits on Repulse and she sank at 12:33. Six aircraft from this wave also attacked Prince of Wales, hitting her with three torpedoes, causing further damage and flooding. Finally, a 500-kilogram (1,100 lb) bomb hit Prince of Wales'''s catapult deck, penetrated to the main deck, where it exploded, causing many casualties in the makeshift aid centre in the Cinema Flat. Several other bombs from this attack scored very near misses, indenting the hull, popping rivets and causing hull plates to split along the seams and intensifying the flooding. At 13:15 the order to abandon ship was given, and at 13:20 Prince of Wales capsized to port, floated for a few brief moments upside down, and sank stern first; Admiral Phillips and Captain Leach were among the 327 fatalities.

### Aftermath

Prince of Wales and Repulse were the first capital ships to be sunk solely by naval air power on the open sea (albeit by land-based rather than carrier-based aircraft), a harbinger of the diminishing role this class of ships was to play in naval warfare thereafter. It is often pointed out, however, that contributing factors to the sinking of Prince of Wales were her surface-scanning radars being inoperable in the humid tropic climate, depriving Force Z of one of its most potent early-warning devices, and the critical early damage she sustained from the first torpedo. Another factor which led to Prince of Wales's demise was the loss of her dynamos, depriving Prince of Wales of many of her electric pumps. Further electrical failures left parts of the ship in total darkness, and added to the difficulties of her damage repair parties as they attempted to counter the flooding. The sinking was the subject of an inquiry chaired by Mr. Justice Bucknill, but the true causes of the ship's loss were only established when divers examined the wreck after the war. The Director of Naval Construction's report on the sinking claimed that the ship's anti-aircraft guns could have inflicted heavy casualties before torpedoes were dropped, if not preventing the successful conclusion of attack had crews been more adequately trained in their operation.[^1]

### The wreck

The wreck lies upside down in 223 feet (68 m) of water at .

A Royal Navy White Ensign attached to a line on a buoy tied to a propeller shaft is periodically renewed. The wreck site was designated a 'Protected Place' in 2001 under the Protection of Military Remains Act 1986, just prior to the 60th anniversary of her sinking. The ship's bell was manually raised in 2002 by British technical divers with the permission of the Ministry of Defence and blessing of the Force Z Survivors Association. It was restored, then presented for display by First Sea Lord and Chief of Naval Staff, Admiral Sir Alan West, to the Merseyside Maritime Museum in Liverpool. The bell has been since moved to the National Museum of the Royal Navy at the Portsmouth Historic Dockyard for display in the Hear My Story Galleries.

In May 2007, Expedition 'Job 74', a dedicated survey of the exterior hull of both Prince of Wales and Repulse, was conducted. The expedition's findings sparked considerable interest among naval architects and marine engineers around the world; as they detailed the nature of the damage to Prince of Wales and the exact location and number of torpedo strike holes. Consequently, the findings contained in the initial expedition report and later supplementary reports were analysed by the SNAME (Society of Naval Architects and Marine Engineers) Marine Forensics Committee and a resultant paper was drawn up entitled Death of a Battleship: A Re-analysis of the Tragic Loss of HMS Prince of Wales, and was subsequently presented at a meeting of RINA (Royal Institution of Naval Architects) and IMarEST (Institute of Marine Engineering, Science & Technology) members in London in 2009 by Mr William Garzke. This report was also presented to the IMarEST, this time in New York, in 2011. However, in 2012 the original paper was updated and expanded (and renamed Death of a Battleship: The Loss of HMS Prince of Wales. A Marine Forensics Analysis of the Sinking) in light of a subsequent diver being able to penetrate deep into the port outer propeller shaft tunnel with a high definition camera, taking photos along the entire length of the propeller shaft all the way to the aft bulkhead of 'B' Engine Room.

In October 2014, the Daily Telegraph reported that both Prince of Wales and Repulse were being "extensively damaged" with explosives by scrap metal dealers.

It is currently traditional for every passing Royal Navy ship to perform a remembrance service over the site of the wrecks.

In May 2023, it was reported that a Chinese ship, Chuan Hong 68, illegally scavenged the wreck for its low-background steel.

### Replica bell for successor

In spring 2019, Cammell Laird was commissioned to make a replica of the ship's bell for the ship's successor, HMS Prince of Wales (R09), the second Queen Elizabeth-class aircraft carrier. The original at the National Museum of the Royal Navy's Portsmouth Historic Dockyard location was surveyed as part of the process.

Cammell Laird were able to contact Utley Offshore in St Helens, the foundry that made both the original bell and 's bell, who still had the original pattern based on the 1908 Admiralty design. Compared to the bronze or bell metal that is used in most modern ship bells, specially sourced nickel silver was used for authenticity. The engraving was done by Shawcross in Birkenhead, while Cammell Laird shipwrights constructed the hardwood base. Cammell Laird COO Tony Graham presented the finished replica to commanding officer Captain Darren Houston during the ship's week-long visit to Liverpool in March 2020.

## Refits

During her career, Prince of Wales was refitted on several occasions, to bring her equipment up to date. The following are the dates and details of the refits undertaken.

[^1]:

Military of Singapore under British rule

World War II battleships of the United Kingdom

World War II shipwrecks in the South China Sea