Topic: Glass

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🔗 Uranium Glass

🔗 Glass

Uranium glass is glass which has had uranium, usually in oxide diuranate form, added to a glass mix before melting for coloration. The proportion usually varies from trace levels to about 2% uranium by weight, although some 20th-century pieces were made with up to 25% uranium.

Uranium glass was once made into tableware and household items, but fell out of widespread use when the availability of uranium to most industries was sharply curtailed during the Cold War in the 1940s to 1990s. Most such objects are now considered antiques or retro-era collectibles, although there has been a minor revival in art glassware. Otherwise, modern uranium glass is now mainly limited to small objects like beads or marbles as scientific or decorative novelties.

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🔗 Prince Rupert's Drop

🔗 Philosophy/Logic 🔗 Glass

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🔗 Nikon F-Mount

🔗 Glass 🔗 Photography

The Nikon F-mount is a type of interchangeable lens mount developed by Nikon for its 35mm format single-lens reflex cameras. The F-mount was first introduced on the Nikon F camera in 1959, and features a three-lug bayonet mount with a 44 mm throat and a flange to focal plane distance of 46.5 mm. The company continues, with the 2020 D6 model, to use variations of the same lens mount specification for its film and digital SLR cameras.

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🔗 Defenestration

🔗 Death 🔗 Glass

Defenestration (from Old French fenestre, inherited from Latin fenestra) is the act of throwing someone or something out of a window. The term was coined around the time of an incident in Prague Castle in the year 1618 which became the spark that started the Thirty Years' War. This was done in "good Bohemian style"; this referred to the defenestration which had occurred in Prague's City Hall almost 200 years earlier (July 1419), which also on that occasion led to war: the Hussite war. The word comes from the New Latin de- (down from) and fenestra (window or opening). Likewise, it can also refer to the condition of being thrown out of a window, as in "The Defenestration of Ermintrude Inch".

While the act of defenestration connotes the forcible or peremptory removal of an adversary, and the term is sometimes used in just that sense, it also suggests breaking the windows in the process (de- also means removal).

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🔗 The Crystal Palace

🔗 Architecture 🔗 London 🔗 England 🔗 United Kingdom 🔗 Citizendium Porting 🔗 Glass 🔗 Kent 🔗 Scouting/Girl Guiding and Girl Scouting 🔗 Scouting

The Crystal Palace was a cast-iron and plate-glass structure originally built in Hyde Park, London, to house the Great Exhibition of 1851. The exhibition took place from 1 May until 15 October 1851, and more than 14,000 exhibitors from around the world gathered in its 990,000 square feet (92,000 m2) exhibition space to display examples of technology developed in the Industrial Revolution. Designed by Joseph Paxton, the Great Exhibition building was 1,851 feet (564 m) long, with an interior height of 128 feet (39 m). It was three times the size of St Paul's Cathedral.

The introduction of the sheet glass method into Britain by Chance Brothers in 1832 made possible the production of large sheets of cheap but strong glass, and its use in the Crystal Palace created a structure with the greatest area of glass ever seen in a building. It astonished visitors with its clear walls and ceilings that did not require interior lights.

It has been suggested that the name of the building resulted from a piece penned by the playwright Douglas Jerrold, who in July 1850 wrote in the satirical magazine Punch about the forthcoming Great Exhibition, referring to a "palace of very crystal".

After the exhibition, the Palace was relocated to an area of South London known as Penge Common. It was rebuilt at the top of Penge Peak next to Sydenham Hill, an affluent suburb of large villas. It stood there from June 1854 until its destruction by fire in November 1936. The nearby residential area was renamed Crystal Palace after the landmark. This included the Crystal Palace Park that surrounds the site, home of the Crystal Palace National Sports Centre, which had previously been a football stadium that hosted the FA Cup Final between 1895 and 1914. Crystal Palace F.C. were founded at the site in 1905 and played at the Cup Final venue in their early years. The park still contains Benjamin Waterhouse Hawkins's Crystal Palace Dinosaurs which date back to 1854.

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🔗 Lycurgus Cup

🔗 London 🔗 British Museum 🔗 Classical Greece and Rome 🔗 History of Science 🔗 Archaeology 🔗 Visual arts 🔗 Glass

The Lycurgus Cup is a 4th-century Roman glass cage cup made of a dichroic glass, which shows a different colour depending on whether or not light is passing through it: red when lit from behind and green when lit from in front. It is the only complete Roman glass object made from this type of glass, and the one exhibiting the most impressive change in colour; it has been described as "the most spectacular glass of the period, fittingly decorated, which we know to have existed".

The cup is also a very rare example of a complete Roman cage-cup, or diatretum, where the glass has been painstakingly cut and ground back to leave only a decorative "cage" at the original surface-level. Many parts of the cage have been completely undercut. Most cage-cups have a cage with a geometric abstract design, but here there is a composition with figures, showing the mythical King Lycurgus, who (depending on the version) tried to kill Ambrosia, a follower of the god Dionysus (Bacchus to the Romans). She was transformed into a vine that twined around the enraged king and restrained him, eventually killing him. Dionysus and two followers are shown taunting the king. The cup is the "only well-preserved figural example" of a cage cup.

The dichroic effect is achieved by making the glass with tiny proportions of nanoparticles of gold and silver dispersed in colloidal form throughout the glass material. The process used remains unclear, and it is likely that it was not well understood or controlled by the makers, and was probably discovered by accidental "contamination" with minutely ground gold and silver dust. The glass-makers may not even have known that gold was involved, as the quantities involved are so tiny; they may have come from a small proportion of gold in any silver added (most Roman silver contains small proportions of gold), or from traces of gold or gold leaf left by accident in the workshop, as residue on tools, or from other work. The very few other surviving fragments of Roman dichroic glass vary considerably in their two colours.

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🔗 Teasmade

🔗 Food and drink 🔗 Glass

A teasmade is a machine for making tea automatically, which was once common in the United Kingdom and some British Commonwealth countries. Teasmades generally include an analogue alarm clock and are designed to be used at the bedside, to ensure tea is ready first thing in the morning. Although crude versions existed in Victorian times, they only became practical with the availability of electric versions in the 1930s. They reached their peak in popularity in the 1960s and 1970s, since when their use has declined, but they are now enjoying a revival, partly as a retro novelty item.

The name teasmade is an example of a genericised trademark, now commonly used to refer to any automatic tea-making appliance.

🔗 Photon Sieve

🔗 Physics 🔗 Telecommunications 🔗 Astronomy 🔗 Electrical engineering 🔗 Glass

A photon sieve is a device for focusing light using diffraction and interference. It consists of a flat sheet of material full of pinholes that are arranged in a pattern which is similar to the rings in a Fresnel zone plate, but a sieve brings light to much sharper focus than a zone plate. The sieve concept, first developed in 2001, is versatile because the characteristics of the focusing behaviour can be altered to suit the application by manufacturing a sieve containing holes of several different sizes and different arrangement of the pattern of holes.

Photon sieves have applications to photolithography. and are an alternative to lenses or mirrors in telescopes and terahertz lenses and antennas.

When the size of sieves is smaller than one wavelength of operating light, the traditional method mentioned above to describe the diffraction patterns is not valid. The vectorial theory must be used to approximate the diffraction of light from nanosieves. In this theory, the combination of coupled-mode theory and multiple expansion method is used to give an analytical model, which can facilitate the demonstration of traditional devices such as lenses and holograms.

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