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Cut Crystal
Cut glass or cut-glass is a technique and a style of decorating glass. For some time the style has often been produced by other techniques such as the use of moulding, but the original technique of cutting glass on an abrasive wheel is still used in luxury products. On glassware vessels, the style typically consists of furrowed faces at angles to each other in complicated patterns, while for lighting fixtures, the style consists of flat or curved facets on small hanging pieces, often all over. Historically, cut glass was shaped using "coldwork" techniques of grinding or drilling, applied as a secondary stage to a piece of glass made by conventional processes such as glassblowing. Today, the glass is often mostly or entirely shaped in the initial process by using a mould (pressed glass), or imitated in clear plastic. Traditional hand-cutting continues, but gives a much more expensive product. Lead glass has long been misleadingly called "crystal" by the industry, evoking the gl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystal Glass
Lead glass, commonly called crystal, is a variety of glass in which lead replaces the calcium content of a typical potash glass. Lead glass contains typically 18–40% (by weight) lead(II) oxide (PbO), while modern lead crystal, historically also known as flint glass due to the original silica source, contains a minimum of 24% PbO. Lead glass is often desirable for a variety of uses due to its clarity. The term ''lead crystal'' is, technically, not an accurate term to describe lead glass, because glass lacks a crystalline structure and is instead an amorphous solid. The use of the term ''lead crystal'' or just "crystal" remains popular for historical and commercial reasons, and because "lead" sounds toxic to consumers. It is retained from the Venetian word ''cristallo'' to describe the rock crystal imitated by Murano glassmakers. This naming convention has been maintained to the present day to describe decorative hollow-ware. Lead crystal glassware was formerly used to store a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mosque Lamp
Mosque lamps of enamelled glass, often with gilding, survive in considerable numbers from the Islamic art of the Middle Ages, especially the 13th and 14th centuries, with Cairo in Egypt and Aleppo and Damascus in Syria the most important centres of production. They are oil lamps, usually with a large round bulbous body rising to a narrower waist, above which the top section is flared. There is usually a foot so they can be placed on a surface, but they were normally used suspended by chains that went through a number of loops on the outside of the body. They were used to light mosques and other buildings in mosque complexes, in large spaces in groups hanging from a circular metal frame. The circular frames continue to be used in many mosques today, but with plain or frosted glass lamps for electric lighting. Manufacture The techniques used are typical of contemporary Islamic glass, with the enamel decoration applied to a pre-fired plain body, and the whole then fired for a sec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emmanuel College Chapel 2, Cambridge, UK - Diliff (cropped)
Immanuel ( he, עִמָּנוּאֵל, 'Īmmānū'ēl, meaning, "God is with us"; also romanized: , ; and or in Koine Greek of the New Testament) is a Hebrew name that appears in the Book of Isaiah (7:14) as a sign that God will protect the House of David. The Gospel of Matthew ( Matthew 1:22 –23) interprets this as a prophecy of the birth of the Messiah and the fulfillment of Scripture in the person of Jesus. ''Immanuel'' "God ( El) with us" is one of the "symbolic names" used by Isaiah, alongside Shearjashub, Maher-shalal-hash-baz, or Pele-joez-el-gibbor-abi-ad-sar-shalom. It has no particular meaning in Jewish messianism. By contrast, the name based on its use in Isaiah 7:14 has come to be read as a prophecy of the Christ in Christian theology following Matthew 1:23, where ''Immanuel'' () is translated as (KJV: "God with us"). Isaiah 7–8 Summary The setting is the Syro-Ephraimite War, 735-734 BCE, which saw the Kingdom of Judah pitted against two northern neig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tariff
A tariff is a tax imposed by the government of a country or by a supranational union on imports or exports of goods. Besides being a source of revenue for the government, import duties can also be a form of regulation of foreign trade and policy that taxes foreign products to encourage or safeguard domestic industry. ''Protective tariffs'' are among the most widely used instruments of protectionism, along with import quotas and export quotas and other non-tariff barriers to trade. Tariffs can be fixed (a constant sum per unit of imported goods or a percentage of the price) or variable (the amount varies according to the price). Taxing imports means people are less likely to buy them as they become more expensive. The intention is that they buy local products instead, boosting their country's economy. Tariffs therefore provide an incentive to develop production and replace imports with domestic products. Tariffs are meant to reduce pressure from foreign competition and reduce th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Putty
Putty is a material with high plasticity, similar in texture to clay or dough, typically used in domestic construction and repair as a sealant or filler. Although some types of putty (typically those using linseed oil) slowly polymerise and become stiff, many putties can be reworked indefinitely, in contrast to other types of filler which typically set solid relatively rapidly. Chemical composition Putty, or lime putty, is made from a mixture of calcium oxide (CaO) and water (H2O) in proportions of 38% and 62% by weight respectively, as result, the solution forms hydrated lime (Ca(OH)2) which takes up about a half of the weight. The other putty mixture may be a calcium carbonate (CaCO3, 750-850 parts) based with a admixtures of CaO (ash calcium, 120-180 parts), white cement (40-60 parts), and talc powders in much lower concentrations (fractions). Applications Use in construction Putty has been used extensively in glazing for fixing and sealing panes of glass into woo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cork (material)
Cork is an Permeability (earth sciences), impermeable buoyancy, buoyant material, the Cork cambium, phellem layer of bark (botany), bark tissue that is harvested for commercial use primarily from ''Quercus suber'' (the cork oak), which is native to southwest Europe and northwest Africa. Cork is composed of suberin, a hydrophobic substance. Because of its impermeable, buoyant, elastic, and fire retardant properties, it is used in a variety of products, the most common of which is wine stoppers. The Dehesa (pastoral management), montado landscape of Portugal produces approximately half of the cork harvested annually worldwide, with Corticeira Amorim being the leading company in the industry. Cork was examined microscopically by Robert Hooke, which led to his discovery and naming of the cell (biology), cell. Cork composition varies depending on Geography, geographic origin, climate and soil conditions, Genetics, genetic origin, tree dimensions, age (virgin or reproduction), and gro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lapping
Lapping is a machining process in which two surfaces are rubbed together with an abrasive between them, by hand movement or using a machine. Lapping often follows other subtractive processes with more aggressive material removal as a first step, such as milling and/or grinding. Lapping can take two forms. The first type of lapping (traditionally often called grinding), involves rubbing a brittle material such as glass against a surface such as iron or glass itself (also known as the "lap" or grinding tool) with an abrasive such as aluminum oxide, jeweller's rouge, optician's rouge, emery, silicon carbide, diamond, etc., between them. This produces microscopic conchoidal fractures as the abrasive rolls about between the two surfaces and removes material from both. The other form of lapping involves a softer material such as pitch or a ceramic for the lap, which is "charged" with the abrasive. The lap is then used to cut a harder material—the workpiece. The abrasive emb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steam Power
A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be transformed, by a connecting rod and crank, into rotational force for work. The term "steam engine" is generally applied only to reciprocating engines as just described, not to the steam turbine. Steam engines are external combustion engines, where the working fluid is separated from the combustion products. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle. In general usage, the term ''steam engine'' can refer to either complete steam plants (including boilers etc.), such as railway steam locomotives and portable engines, or may refer to the piston or turbine machinery alone, as in the beam engine and stationary steam engine. Although steam-driven devices were known as early as the aeolipile in the first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Treadle
A treadle (from oe, tredan, "to tread") is a mechanism operated with a pedal for converting reciprocating motion into rotating motion. Along with cranks, treadmills, and treadwheels, treadles allow human and animal machine power in the absence of electricity. Before the widespread availability of electric power, treadles were widely used to power a range of machines. They may still be used as a matter of preference or in environments where electric power is not available. Operation and uses A treadle is operated by pressing down on its pedal with one or both feet, causing a rocking motion. This movement can then be stored as rotational motion via a crankshaft driving a flywheel. Alternatively, energy can be stored in a spring as in the pole lathe. Treadles were once used extensively to power most machines including lathes, rotating or reciprocating saws, spinning wheels, looms, and sewing machines. The last use was popularized by Elias Howe and Isaac Singer in the eponym ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pliny The Elder
Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic ''Naturalis Historia'' (''Natural History''), which became an editorial model for encyclopedias. He spent most of his spare time studying, writing, and investigating natural and geographic phenomena in the field. His nephew, Pliny the Younger, wrote of him in a letter to the historian Tacitus: Among Pliny's greatest works was the twenty-volume work ''Bella Germaniae'' ("The History of the German Wars"), which is no longer extant. ''Bella Germaniae'', which began where Aufidius Bassus' ''Libri Belli Germanici'' ("The War with the Germans") left off, was used as a source by other prominent Roman historians, including Plutarch, Tacitus and Suetonius. Tacitus—who many scholars agree had never travelled in Germania—used ''Bella Germani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refraction
In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomenon, but other waves such as sound waves and water waves also experience refraction. How much a wave is refracted is determined by the change in wave speed and the initial direction of wave propagation relative to the direction of change in speed. For light, refraction follows Snell's law, which states that, for a given pair of media, the ratio of the sines of the angle of incidence ''θ1'' and angle of refraction ''θ2'' is equal to the ratio of phase velocities (''v''1 / ''v''2) in the two media, or equivalently, to the refractive indices (''n''2 / ''n''1) of the two media. :\frac =\frac=\frac Optical prisms and lenses use refraction to redirect light, as does the human eye. The refractive index of materials varies with the wavelengt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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