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United States Navy
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The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U. S. Navy is the largest, most capable navy in the world, the U. S. Navy has the worlds largest aircraft carrier fleet, with ten in service, two in the reserve fleet, and three new carriers under construction. The service has 323,792 personnel on duty and 108,515 in the Navy Reserve. It has 274 deployable combat vessels and more than 3,700 operational aircraft as of October 2016, the U. S. Navy traces its origins to the Continental Navy, which was established during the American Revolutionary War and was effectively disbanded as a separate entity shortly thereafter. It played a role in the American Civil War by blockading the Confederacy. It played the role in the World War II defeat of Imperial Japan. The 21st century U. S. Navy maintains a global presence, deploying in strength in such areas as the Western Pacific, the Mediterranean. The Navy is administratively managed by the Department of the Navy, the Department of the Navy is itself a division of the Department of Defense, which is headed by the Secretary of Defense. The Chief of Naval Operations is an admiral and the senior naval officer of the Department of the Navy. The CNO may not be the highest ranking officer in the armed forces if the Chairman or the Vice Chairman of the Joint Chiefs of Staff. The mission of the Navy is to maintain, train and equip combat-ready Naval forces capable of winning wars, deterring aggression, the United States Navy is a seaborne branch of the military of the United States. The Navys three primary areas of responsibility, The preparation of naval forces necessary for the prosecution of war. The development of aircraft, weapons, tactics, technique, organization, U. S. Navy training manuals state that the mission of the U. S. Armed Forces is to prepare and conduct prompt and sustained combat operations in support of the national interest, as part of that establishment, the U. S. Navys functions comprise sea control, power projection and nuclear deterrence, in addition to sealift duties. It follows then as certain as that night succeeds the day, that without a decisive naval force we can do nothing definitive, the Navy was rooted in the colonial seafaring tradition, which produced a large community of sailors, captains, and shipbuilders. In the early stages of the American Revolutionary War, Massachusetts had its own Massachusetts Naval Militia, the establishment of a national navy was an issue of debate among the members of the Second Continental Congress. Supporters argued that a navy would protect shipping, defend the coast, detractors countered that challenging the British Royal Navy, then the worlds preeminent naval power, was a foolish undertaking. Commander in Chief George Washington resolved the debate when he commissioned the ocean-going schooner USS Hannah to interdict British merchant ships, and reported the captures to the Congress
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Naval History and Heritage Command
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When the British invaded Washington in 1814 this collection, containing the finest works on naval history from America and abroad, was rushed to safety outside the Federal City. Thereafter the library had many locations, including a specially designed space in the State, War and he also began to collect and preserve naval records, particularly those of the American Civil War. Congress initially recognized his efforts by authorizing funds for staff and combining the library and records sections into the Office of Library. In 1915 the appropriations for publications, the library, and naval war records were combined, once America entered World War I, emphasis shifted to gathering documents on current naval operations. To handle World War I records in Washington, a Historical Section was established in the Office of the Chief of Naval Operations and housed in the new Navy Department Building on Constitution Avenue. When the war ended, Admiral Sims London collection, as well as photographs, the library, by now holding more than 50,000 volumes, remained in the State, War, and Navy Building. In 1921, a member of Admiral Sims wartime staff, Captain Dudley W. Knox, was named head of the Office of Naval Records and Library. For the next years he was the driving force behind the Navys historical program, earning for the office an international reputation in the field of naval archives. The Historical Section was absorbed into Naval Records and Library in 1927, knoxs additional appointment as the Curator for the Navy envisioned a display of our nations sea heritage in a naval museum in Washington. In 1961, Admiral Arleigh Burke, Chief of Naval Operations, at President Franklin D. Roosevelts suggestion, Knox began several documentary series. Seven volumes pertaining to the Quasi War with France and seven volumes relating to the war with the Barbary Powers were ultimately published, World War II halted plans for similar publications on the American Revolution, the War of 1812, the Mexican–American War, and World War I. During World War II, Knox turned his attention to collecting documents generated by operations in the global conflict. Knox served as Deputy Director of Naval History under the Director, in 1952 it was renamed the Naval History Division. The eventual home for the Navys historians was the Washington Navy Yard in Southeast Washington, the first component of the Naval History Division located in the yard was the Navy Museum, established in 1961. In 1963, the Operational Archives moved to the Navy Yard, the other sections of the Naval History Division followed in 1970, occupying several scattered buildings. An organizational change in 1971 shifted the Naval History Division from an establishment to a field activity called the Naval Historical Center, under the Chief of Naval Operations. In 1986, the Navy Art Collection and Gallery and the Naval Aviation History and Publication Division,2008 was a year of change for the Navys history program. First, the command was streamlined into four components, Histories and Archives, Museums and Collections, Integration and Outreach
3.
Engraving
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Engraving is the practice of incising a design onto a hard, usually flat surface by cutting grooves into it. Wood engraving is a form of printing and is not covered in this article. Engraving was an important method of producing images on paper in artistic printmaking, in mapmaking. Other terms often used for printed engravings are copper engraving, copper-plate engraving or line engraving, hand engraving is a term sometimes used for engraving objects other than printing plates, to inscribe or decorate jewellery, firearms, trophies, knives and other fine metal goods. Traditional engravings in printmaking are also engraved, using just the same techniques to make the lines in the plate. Each graver is different and has its own use, engravers use a hardened steel tool called a burin, or graver, to cut the design into the surface, most traditionally a copper plate. Modern professional engravers can engrave with a resolution of up to 40 lines per mm in high grade work creating game scenes, dies used in mass production of molded parts are sometimes hand engraved to add special touches or certain information such as part numbers. In addition to engraving, there are engraving machines that require less human finesse and are not directly controlled by hand. They are usually used for lettering, using a pantographic system, there are versions for the insides of rings and also the outsides of larger pieces. Such machines are used for inscriptions on rings, lockets. Gravers come in a variety of shapes and sizes that yield different line types, the burin produces a unique and recognizable quality of line that is characterized by its steady, deliberate appearance and clean edges. The angle tint tool has a curved tip that is commonly used in printmaking. Florentine liners are flat-bottomed tools with multiple lines incised into them, ring gravers are made with particular shapes that are used by jewelry engravers in order to cut inscriptions inside rings. Flat gravers are used for work on letters, as well as wriggle cuts on most musical instrument engraving work, remove background. Knife gravers are for line engraving and very deep cuts, round gravers, and flat gravers with a radius, are commonly used on silver to create bright cuts, as well as other hard-to-cut metals such as nickel and steel. Square or V-point gravers are typically square or elongated diamond-shaped and used for cutting straight lines, V-point can be anywhere from 60 to 130 degrees, depending on purpose and effect. These gravers have very small cutting points, other tools such as mezzotint rockers, roulets and burnishers are used for texturing effects. Burnishing tools can also be used for stone setting techniques
4.
Old master print
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An old master print is a work of art produced by a printing process within the Western tradition. Fifteenth-century prints are rare that they are classed as old master prints even if they are of crude or merely workmanlike artistic quality. A date of about 1830 is usually taken as marking the end of the period whose prints are covered by this term, the main techniques used, in order of their introduction, are woodcut, engraving, etching, mezzotint and aquatint, although there are others. Different techniques are combined in a single print. With rare exceptions printed on textiles, such as silk, or on vellum, many great European artists, such as Albrecht Dürer, Rembrandt, and Francisco Goya, were dedicated printmakers. In their own day, their international reputations largely came from their prints, influences between artists were also mainly transmitted beyond a single city by prints, for the same reason. Prints therefore are frequently brought up in detailed analyses of individual paintings in art history, today, thanks to colour photo reproductions, and public galleries, their paintings are much better known, whilst their prints are only rarely exhibited, for conservation reasons. But some museum print rooms allow visitors to see their collection, the oldest technique is woodcut, or woodblock printing, which was invented as a method for printing on cloth in China, and perhaps separately in Egypt in the Byzantine period. This had reached Europe via the Byzantine or Islamic worlds before 1300, religious images and playing cards are documented as being produced on paper, probably printed, by a German in Bologna in 1395. However, the most impressive printed European images to survive from before 1400 are printed on cloth, for use as hangings on walls or furniture, including altars, some were used as a pattern to embroider over. Some religious images were used as bandages, to speed healing, the earliest print images are mostly of a high artistic standard, and were clearly designed by artists with a background in painting. Whether these artists cut the blocks themselves, or only inked the design on the block for another to carve, is not known, the great majority of surviving 15th-century prints are religious, although these were probably the ones more likely to survive. Their makers were sometimes called Jesus maker or saint-maker in documents, as with manuscript books, monastic institutions sometimes produced, and often sold, prints. No artists can be identified with specific woodcuts until towards the end of the century, the little evidence we have suggests that woodcut prints became relatively common and cheap during the fifteenth century, and were affordable by skilled workers in towns. For example, what may be the earliest surviving Italian print, the school caught fire, and the crowd who gathered to watch saw the print carried up into the air by the fire, before falling down into the crowd. This was regarded as an escape and the print was carried to Forlì Cathedral. Like the majority of prints before approximately 1460, only a single impression of this print has survived, Woodcut blocks are printed with light pressure, and are capable of printing several thousand impressions, and even at this period some prints may well have been produced in that quantity. Many prints were hand-coloured, mostly in watercolour, in fact the hand-colouring of prints continued for many centuries, Italy, Germany, France and the Netherlands were the main areas of production, England does not seem to have produced any prints until about 1480
5.
Magazine
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A magazine is a publication, usually a periodical publication, which is printed or electronically published. Magazines are generally published on a schedule and contain a variety of content. They are generally financed by advertising, by a price, by prepaid subscriptions. At its root, the magazine refers to a collection or storage location. In the case of written publication, it is a collection of written articles and this explains why magazine publications share the word root with gunpowder magazines, artillery magazines, firearms magazines, and, in French, retail stores such as department stores. By definition, a magazine paginates with each issue starting at three, with the standard sizing being 8 3/8 ×10 7/8 inches. However, in the sense a journal has continuous pagination throughout a volume. Some professional or trade publications are also peer-reviewed, an example being the Journal of Accountancy, academic or professional publications that are not peer-reviewed are generally professional magazines. That a publication calls itself a journal does not make it a journal in the technical sense, magazines can be distributed through the mail, through sales by newsstands, bookstores, or other vendors, or through free distribution at selected pick-up locations. The subscription business models for distribution fall into three main categories. In this model, the magazine is sold to readers for a price, either on a basis or by subscription. Paid circulation allows for defined readership statistics and this means that there is no cover price and issues are given away, for example in street dispensers, airline, or included with other products or publications. Because this model involves giving issues away to unspecific populations, the statistics only entail the number of issues distributed and this is the model used by many trade magazines distributed only to qualifying readers, often for free and determined by some form of survey. This allows a level of certainty that advertisements will be received by the advertisers target audience. This latter model was used before the rise of the World Wide Web and is still employed by some titles. For example, in the United Kingdom, a number of computer-industry magazines use this model, including Computer Weekly and Computing, for the global media industry, an example would be VideoAge International. The earliest example of magazines was Erbauliche Monaths Unterredungen, a literary and philosophy magazine, the Gentlemans Magazine, first published in 1731, in London was the first general-interest magazine. Edward Cave, who edited The Gentlemans Magazine under the pen name Sylvanus Urban, was the first to use the term magazine, founded by Herbert Ingram in 1842, The Illustrated London News was the first illustrated magazine
6.
Painting
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Painting is the practice of applying paint, pigment, color or other medium to a solid surface. The medium is commonly applied to the base with a brush, but other implements, such as knives, sponges, Painting is a mode of creative expression, and the forms are numerous. Drawing, gesture, composition, narration, or abstraction, among other aesthetic modes, may serve to manifest the expressive, Paintings can be naturalistic and representational, photographic, abstract, narrative, symbolistic, emotive, or political in nature. A portion of the history of painting in both Eastern and Western art is dominated by motifs and ideas. In art, the term painting describes both the act and the result of the action, the term painting is also used outside of art as a common trade among craftsmen and builders. What enables painting is the perception and representation of intensity, every point in space has different intensity, which can be represented in painting by black and white and all the gray shades between. In practice, painters can articulate shapes by juxtaposing surfaces of different intensity, thus, the basic means of painting are distinct from ideological means, such as geometrical figures, various points of view and organization, and symbols. In technical drawing, thickness of line is ideal, demarcating ideal outlines of an object within a perceptual frame different from the one used by painters. Color and tone are the essence of painting as pitch and rhythm are the essence of music, color is highly subjective, but has observable psychological effects, although these can differ from one culture to the next. Black is associated with mourning in the West, but in the East, some painters, theoreticians, writers and scientists, including Goethe, Kandinsky, and Newton, have written their own color theory. Moreover, the use of language is only an abstraction for a color equivalent, the word red, for example, can cover a wide range of variations from the pure red of the visible spectrum of light. There is not a register of different colors in the way that there is agreement on different notes in music. For a painter, color is not simply divided into basic, painters deal practically with pigments, so blue for a painter can be any of the blues, phthalocyanine blue, Prussian blue, indigo, cobalt, ultramarine, and so on. Psychological and symbolical meanings of color are not, strictly speaking, colors only add to the potential, derived context of meanings, and because of this, the perception of a painting is highly subjective. The analogy with music is quite clear—sound in music is analogous to light in painting, shades to dynamics and these elements do not necessarily form a melody of themselves, rather, they can add different contexts to it. Modern artists have extended the practice of painting considerably to include, as one example, collage, some modern painters incorporate different materials such as sand, cement, straw or wood for their texture. Examples of this are the works of Jean Dubuffet and Anselm Kiefer, there is a growing community of artists who use computers to paint color onto a digital canvas using programs such as Adobe Photoshop, Corel Painter, and many others. These images can be printed onto traditional canvas if required, rhythm is important in painting as it is in music
7.
Steel engraving
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Steel engraving is a technique for printing illustrations based on steel instead of copper. It has been used in artistic printmaking, although it was much used for reproductions in the 19th century. Steel engraving was introduced in 1792 by Jacob Perkins, an American inventor, for banknote printing, the new technique only partially replaced the other commercial techniques of that time such as woodcut, wood engraving, copper engraving and later lithography. All the illustrations in the Encyclopædia Britannica of 1911 are steel engravings, Engraving is done with a burin, which is a small bar of hardened steel with a sharp point. It is pushed along the plate to produce thin furrowed lines and this is followed by the use of a scraper to remove any burs, since they would be an impediment during the subsequent inking process. Steel plates are very hard for this technique, which is used on softer copper plates. So steel engraving also used etching, where acid creates the lines in the plates in the pattern made by removing a thin coating of acid-resistant ground by tools. Roulettes of different types were used together with the burin and needle to create densely packed marks which appear as tonal to the eye, true burin engraving was generally used to finish the etched image. First a broad, general outline is made on the plate before starting the detailed image, Engraving will produce a printed reverse or mirror image of the image on the plate. Steel plates can be hardened to ensure that they can print thousands of times with little wear. From about 1860 the steel-facing of copper plates became widely used and it can be very difficult to distinguish between engravings on steel and steel-faced copper, other than by date. The most reliable way of distinguishing between unfaced copper engraving and steel or steel-faced engraving is the lightness and delicacy of the lines in the latter. Until around 1820 copper plates were the medium used for engraving. Copper, being a metal, was easy to carve or engrave. Engravers then reworked a worn plate by retracing the previous engraving to sharpen the image again, another advantage to using copper is that it is a soft metal and can be corrected or updated with a reasonable amount of effort. For this reason, copper plates were the medium of printing for mapmakers. During the 1820s steel began to copper as the preferred medium of commercial publishers for illustration. Steel engraving produced plates with shaper, harder, more distinct lines, also, the harder steel plates produced much longer wearing dies that could strike thousands of copies before they would need any repair or refurbishing engraving
8.
Etching
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Etching is traditionally the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio in the metal. In modern manufacturing, other chemicals may be used on other types of material, as a method of printmaking, it is, along with engraving, the most important technique for old master prints, and remains in wide use today. In a number of variants such as microfabrication etching and photochemical milling it is a crucial technique in much modern technology. In traditional pure etching, a plate is covered with a waxy ground which is resistant to acid. The artist then scratches off the ground with an etching needle where he or she wants a line to appear in the finished piece. The échoppe, a tool with an oval section, is also used for swelling lines. The plate is dipped in a bath of acid, technically called the mordant or etchant. The acid bites into the metal where it is exposed, leaving behind lines sunk into the plate, the remaining ground is then cleaned off the plate. The plate is inked all over, and then the ink wiped off the surface, the plate is then put through a high-pressure printing press together with a sheet of paper. The paper picks up the ink from the lines, making a print. The process can be repeated many times, typically several hundred impressions could be printed before the shows much sign of wear. The work on the plate can also be added to by repeating the whole process, Etching has often been combined with other intaglio techniques such as engraving or aquatint. The process as applied to printmaking is believed to have been invented by Daniel Hopfer of Augsburg, Hopfer was a craftsman who decorated armour in this way, and applied the method to printmaking, using iron plates. Apart from his prints, there are two examples of his work on armour, a shield from 1536 now in the Real Armeria of Madrid. The switch to copper plates was made in Italy. On the other hand, the handling of the ground and acid need skill and experience, prior to 1100 AD, the New World Hohokam independently utilized the technique of acid etching in marine shell designs. Jacques Callot from Nancy in Lorraine made important technical advances in etching technique and he developed the échoppe, a type of etching-needle with a slanting oval section at the end, which enabled etchers to create a swelling line, as engravers were able to do. Callot also appears to have responsible for an improved, harder, recipe for the etching ground
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Photography
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Typically, a lens is used to focus the light reflected or emitted from objects into a real image on the light-sensitive surface inside a camera during a timed exposure. With an electronic sensor, this produces an electrical charge at each pixel. A negative image on film is used to photographically create a positive image on a paper base, known as a print. The word photography was created from the Greek roots φωτός, genitive of φῶς, light and γραφή representation by means of lines or drawing, several people may have coined the same new term from these roots independently. Johann von Maedler, a Berlin astronomer, is credited in a 1932 German history of photography as having used it in an article published on 25 February 1839 in the German newspaper Vossische Zeitung. Both of these claims are now widely reported but apparently neither has ever been confirmed as beyond reasonable doubt. Credit has traditionally given to Sir John Herschel both for coining the word and for introducing it to the public. Photography is the result of combining several technical discoveries, later Greek mathematicians Aristotle and Euclid also independently described a pinhole camera in the 5th and 4th centuries BCE. Daniele Barbaro described a diaphragm in 1566, wilhelm Homberg described how light darkened some chemicals in 1694. The fiction book Giphantie, published in 1760, by French author Tiphaigne de la Roche, the discovery of the camera obscura that provides an image of a scene dates back to ancient China. Leonardo da Vinci mentions natural camera obscura that are formed by dark caves on the edge of a sunlit valley, a hole in the cave wall will act as a pinhole camera and project a laterally reversed, upside down image on a piece of paper. So the birth of photography was primarily concerned with inventing means to capture, renaissance painters used the camera obscura which, in fact, gives the optical rendering in color that dominates Western Art. The camera obscura literally means dark chamber in Latin and it is a box with a hole in it which allows light to go through and create an image onto the piece of paper. Around the year 1800, British inventor Thomas Wedgwood made the first known attempt to capture the image in a camera obscura by means of a light-sensitive substance and he used paper or white leather treated with silver nitrate. The shadow images eventually darkened all over, the first permanent photoetching was an image produced in 1822 by the French inventor Nicéphore Niépce, but it was destroyed in a later attempt to make prints from it. Niépce was successful again in 1825, in 1826 or 1827, he made the View from the Window at Le Gras, the earliest surviving photograph from nature. Because Niépces camera photographs required a long exposure, he sought to greatly improve his bitumen process or replace it with one that was more practical. With an eye to eventual commercial exploitation, the partners opted for total secrecy, Daguerres efforts culminated in what would later be named the daguerreotype process
10.
Printmaking
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Printmaking is the process of making artworks by printing, normally on paper. Printmaking normally covers only the process of creating prints that have an element of originality, except in the case of monotyping, the process is capable of producing multiples of the same piece, which is called a print. Each print produced is not considered a copy but rather is considered an original, a print may be known as an impression. Printmaking is not chosen only for its ability to multiple impressions. Prints are created by transferring ink from a matrix or through a screen to a sheet of paper or other material. Screens made of silk or synthetic fabrics are used for the screenprinting process, other types of matrix substrates and related processes are discussed below. Multiple impressions printed from the matrix form an edition. Prints may also be printed in book form, such as illustrated books or artists books, Printmaking techniques are generally divided into the following basic categories, Relief, where ink is applied to the original surface of the matrix. Relief techniques include woodcut or woodblock as the Asian forms are known, wood engraving. Intaglio, where ink is applied beneath the surface of the matrix. Intaglio techniques include engraving, etching, mezzotint, aquatint, planographic, where the matrix retains its original surface, but is specially prepared and/or inked to allow for the transfer of the image. Planographic techniques include lithography, monotyping, and digital techniques, stencil, where ink or paint is pressed through a prepared screen, including screenprinting and pochoir. Other types of printmaking techniques outside these groups include collagraphy and viscosity printing, collagraphy is a printmaking technique in which textured material is adhered to the printing matrix. This texture is transferred to the paper during the printing process, Contemporary printmaking may include digital printing, photographic mediums, or a combination of digital, photographic, and traditional processes. Many of these techniques can also be combined, especially within the same family, for example, Rembrandts prints are usually referred to as etchings for convenience, but very often include work in engraving and drypoint as well, and sometimes have no etching at all. Woodcut, a type of print, is the earliest printmaking technique. It was probably first developed as a means of printing patterns on cloth, woodcuts of images on paper developed around 1400 in Japan, and slightly later in Europe. These are the two areas where woodcut has been most extensively used purely as a process for making images without text, the artist draws a design on a plank of wood, or on paper which is transferred to the wood
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Intaglio (printmaking)
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Intaglio is the family of printing and printmaking techniques in which the image is incised into a surface and the incised line or sunken area holds the ink. It is the direct opposite of a relief print, normally, copper or zinc plates are used as a surface or matrix, and the incisions are created by etching, engraving, drypoint, aquatint or mezzotint. Collagraphs may also be printed as intaglio plates, in etching, for example, the plate is covered in a resin ground or an acid-resistant wax material. Using an etching needle, or a tool, the image is engraved into the ground. The plate is dipped into acid. The acid bites into the surface of the plate where it was exposed, biting is a printmaking term to describe the acids etching, or incising, of the image. After the plate is bitten, the plate is removed from the acid bath. To print an intaglio plate, ink is applied to the surface by wiping and/or dabbing the plate to push the ink into the recessed lines, the plate is then rubbed with tarlatan cloth to remove most of the excess ink. The final smooth wipe is often done with newspaper or old public phone book pages, a damp piece of paper is placed on top of the plate, so that when going through the press the damp paper will be able to be squeezed into the plates ink-filled grooves. The paper and plate are covered by a thick blanket to ensure even pressure when going through the rolling press. The rolling press applies very high pressure through the blanket to push the paper into the grooves on the plate, the blanket is then lifted, revealing the paper and printed image. Martin Schongauer was one of the earliest known artists to exploit the copper-engraving technique, italian and Netherlandish engraving began slightly after the Germans, but were well developed by 1500. Drypoint and etching were also German inventions of the century, probably by the Housebook Master. In the nineteenth century, Viennese printer Karel Klíč introduced a combined intaglio, photogravure retained the smooth continuous tones of photography but was printed using a chemically-etched copper plate. This permitted a photographic image to be printed on regular paper, at one time intaglio printing was used for all mass-printed materials including banknotes, stock certificates, newspapers and magazines, fabrics, wallpapers and sheet music. Today intaglio engraving is largely used for paper or plastic currency, banknotes, passports, photogravure, an intaglio photo-printmaking process Rotogravure Line engraving Viscosity printing History of printing Intaglio and other printmaking definitions
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Wood engraving
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Wood engraving is a printmaking and letterpress printing technique, in which an artist works an image or matrix of images into a block of wood. Functionally a variety of woodcut, it uses relief printing, where the artist applies ink to the face of the block and prints using relatively low pressure. By contrast, ordinary engraving, like etching, uses a metal plate for the matrix, and is printed by the method, where the ink fills the valleys. As a result, wood engravings deteriorate less quickly than copper-plate engravings, Thomas Bewick developed the wood engraving technique at the end of the 18th century. His work differed from earlier woodcuts in two key ways, first, rather than using woodcarving tools such as knives, Bewick used an engravers burin. With this, he could create thin delicate lines, often creating large areas in the composition. Second, wood engraving traditionally uses the woods end grain—while the older technique used the side grain. The resulting increased hardness and durability facilitated more detailed images, wood-engraved blocks could be used on conventional printing presses, which were going through rapid mechanical improvements during the first quarter of the 19th century. The blocks were made the same height as, and composited alongside, the combination of this new wood engraving method and mechanized printing drove a rapid expansion of illustrations in the 19th century. Further, advances in stereotype let wood-engravings be reproduced onto metal, by the mid-19th century, many wood engravings rivaled copperplate engravings. In 15th and 16th-century Europe, woodcuts were a technique in printmaking and printing. They were still made for printing press work such as newspapers or almanacs. The beginnings of modern wood engraving techniques developed at the end of the 18th and beginning of the 19th century, Bewick generally engraved harder woods, such as boxwood, rather than the woods used in woodcuts, and he engraved the ends of blocks instead of the side. Finding a woodcutting knife not suitable for working against the grain in harder woods, Bewick used a burin, from the beginning of the nineteenth century Bewicks techniques gradually came into wider use, especially in Britain and the United States. Alexander Anderson introduced the technique to the United States, Bewicks work impressed him, so he reverse engineered and imitated Bewicks technique—using metal until he learned that Bewick used wood. This was, in ways a unnatural application, since engravers had to cut away almost all the surface of the block to produce the printable lines of the artists drawing. Nonetheless, it became the most common use of wood engraving, in the United States, wood-engraved publications also began to take hold, such as Harpers Weekly. A single design was divided into a grid, and each worked on a square
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Relief printing
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Relief printing is a process where protruding surface faces of the printing plate or block are inked, recessed areas are ink free. Printing the image is therefore a simple matter of inking the face of the matrix. A printing-press may not be needed as the back of the paper can be rubbed or pressed by hand with a tool such as a brayer or roller. The matrix in relief printing is classically created by starting with a flat original surface, the remaining areas of the original surface receive the ink. The relief family of techniques includes woodcut, metalcut, wood engraving, relief etching, linocut, rubber stamp, foam printing, potato printing, traditional text printing with movable type is also a relief technique. This meant that woodcuts were much easier to use as book illustrations, intaglio illustrations, such as engravings, had to be printed separately. Relief printing is one of the families of printmaking techniques, along with the intaglio. Modern developments have created other types, in contrast, in the intaglio process the recessed areas are the printed areas. The whole matrix is inked, and the ink then wiped away from the surface, much greater pressure is then needed to force the paper into the channels containing the ink, and a high-pressure press will normally be required. Intaglio techniques include engraving, etching, and drypoint, with planographic techniques, such as lithography, the entire surface of the matrix is flat, and some areas are treated to create the print image. Normally relief and intaglio techniques can only be mixed with others of the family in the same work. See also Relief printing techniques as used and described by French printmaker Dominique Lecomte
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Aztec
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The Aztec people were certain ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl language and who dominated large parts of Mesoamerica from the 14th to 16th centuries. The Nahuatl words aztecatl and aztecah mean people from Aztlan, a place for the Nahuatl-speaking culture of the time. Often the term Aztec refers exclusively to the Mexica people of Tenochtitlan, situated on an island in Lake Texcoco, who referred to themselves as Mēxihcah Tenochcah or Cōlhuah Mexihcah. From the 13th century, the Valley of Mexico was the heart of Aztec civilization, here the capital of the Aztec Triple Alliance, the Triple Alliance formed a tributary empire expanding its political hegemony far beyond the Valley of Mexico, conquering other city states throughout Mesoamerica. At its pinnacle, Aztec culture had rich and complex mythological and religious traditions, as well as achieving remarkable architectural and artistic accomplishments. Subsequently, the Spanish founded the new settlement of Mexico City on the site of the ruined Aztec capital, the term extends to further ethnic groups associated with the Aztec empire such as the Acolhua and Tepanec and others that were incorporated into the empire. In older usage the term was used about modern Nahuatl speaking ethnic groups. In recent usage these ethnic groups are referred to as the Nahua peoples. Linguistically the term Aztecan is still used about the branch of the Uto-Aztecan languages that includes the Nahuatl language and its closest relatives Pochutec, to the Aztecs themselves the word aztec was not an endonym for any particular ethnic group. Rather it was a term used to refer to several ethnic groups, not all of them Nahuatl speaking. In the Nahuatl language aztecatl means person from Aztlan and this usage has been the subject of debate in more recent years, but the term Aztec is still more common. For the same reason the notion of Aztec civilization is best understood as a horizon of a general Mesoamerican civilization. Particular to the Aztecs of Tenochtitlan was the Mexica patron God Huitzilopochtli, twin pyramids, the Aztec Empire was a tribute empire based in Tenochtitlan that extended its power throughout Mesoamerica in the late postclassic period. Soon Texcoco and Tlacopan became junior partners in the alliance, which was de facto led by the Mexica of Tenochtitlan, the empire extended its power by a combination of trade and military conquest. The political clout of the empire reached far south into Mesoamerica conquering cities as far south as Chiapas and Guatemala, the Nahua peoples began to migrate into Mesoamerica from northern Mexico in the 6th century. They populated central Mexico, dislocating speakers of Oto-Manguean languages as they spread their influence south. As the former nomadic hunter-gatherer peoples mixed with the civilizations of Mesoamerica, adopting religious and cultural practices. During the Postclassic period they rose to power at such sites as Tula, in the 12th century the Nahua power center was in Azcapotzalco, from where the Tepanecs dominated the valley of Mexico
15.
Alexander von Humboldt
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Friedrich Wilhelm Heinrich Alexander von Humboldt was a Prussian geographer, naturalist, explorer, and influential proponent of Romantic philosophy and science. He was the brother of the Prussian minister, philosopher. Humboldts quantitative work on botanical geography laid the foundation for the field of biogeography, Humboldts advocacy of long-term systematic geophysical measurement laid the foundation for modern geomagnetic and meteorological monitoring. Between 1799 and 1804, Humboldt travelled extensively in Latin America and his description of the journey was written up and published in an enormous set of volumes over 21 years. Humboldt was one of the first people to propose that the lands bordering the Atlantic Ocean were once joined and this important work also motivated a holistic perception of the universe as one interacting entity. Alexander von Humboldt was born in Berlin in Prussia on 14 September 1769 and he was baptized as a baby in the Lutheran faith, with the Duke of Brunswick serving as godfather. At age 42, Alexander Georg was rewarded for his services in the Seven Years War with the post of Royal Chamberlain and he profited from the contract to lease state lotteries and tobacco sales. He first married the daughter of Prussian General Adjutant Schweder, in 1766, Alexander Georg married Maria Elisabeth Colomb, a well-educated woman and widow of Baron Hollwede, with whom she had a son. Alexander Georg and Maria Elisabeth had three children, a daughter, who died young, and then two sons, Wilhelm and Alexander and her first-born son, Wilhelms and Alexanders half-brother, was something of a neer do well, not often mentioned in the family history. Alexander Georg died in 1779, leaving the brothers Humboldt in the care of their emotionally distant mother, Humboldts mother expected them to become civil servants of the Prussian state. The money Baron Holwede left to Alexanders mother became, after her death, instrumental in funding Alexanders explorations, due to his youthful penchant for collecting and labeling plants, shells and insects, Alexander received the playful title of the little apothecary. On April 25,1789, he matriculated at Göttingen, then known for the lectures of C. G. Heyne and his brother Wilhelm was already a student at Göttingen, but they did not interact much since their intellectual interests were quite different. His vast and varied interests were by this time fully developed, at Göttingen he met Georg Forster, a naturalist who had been with Captain James Cook on his second voyage. Humboldt traveled with Forster in Europe, the two traveled to England, Humboldts first sea voyage, The Netherlands, and France. In England, he met Sir Joseph Banks, President of the Royal Society, the scientific friendship between Banks and Humboldt lasted until Bankss death in 1820, and the two shared botanical specimens for study. Banks also mobilized his scientific contacts in later years to aid Humboldts work, Humboldts scientific excursion up the Rhine resulted in his 1790 treatise Mineralogische Beobachtungen über einige Basalte am Rhein. Humboldts passion for travel was of long standing, Humboldts talents were devoted to the purpose of preparing himself as a scientific explorer. During this period, his brother Wilhelm married, but Alexander did not attend the nuptials, Humboldt graduated from the Freiberg School of Mines in 1792 and was appointed to a Prussian government position in the Department of Mines as an inspector in Bayreuth and the Fichtel mountains
16.
Mexico
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Mexico, officially the United Mexican States, is a federal republic in the southern half of North America. It is bordered to the north by the United States, to the south and west by the Pacific Ocean, to the southeast by Guatemala, Belize, and the Caribbean Sea, and to the east by the Gulf of Mexico. Covering almost two million square kilometers, Mexico is the sixth largest country in the Americas by total area, Mexico is a federation comprising 31 states and a federal district that is also its capital and most populous city. Other metropolises include Guadalajara, Monterrey, Puebla, Toluca, Tijuana, pre-Columbian Mexico was home to many advanced Mesoamerican civilizations, such as the Olmec, Toltec, Teotihuacan, Zapotec, Maya and Aztec before first contact with Europeans. In 1521, the Spanish Empire conquered and colonized the territory from its base in Mexico-Tenochtitlan, Three centuries later, this territory became Mexico following recognition in 1821 after the colonys Mexican War of Independence. The tumultuous post-independence period was characterized by instability and many political changes. The Mexican–American War led to the cession of the extensive northern borderlands, one-third of its territory. The Pastry War, the Franco-Mexican War, a civil war, the dictatorship was overthrown in the Mexican Revolution of 1910, which culminated with the promulgation of the 1917 Constitution and the emergence of the countrys current political system. Mexico has the fifteenth largest nominal GDP and the eleventh largest by purchasing power parity, the Mexican economy is strongly linked to those of its North American Free Trade Agreement partners, especially the United States. Mexico was the first Latin American member of the Organisation for Economic Co-operation and Development and it is classified as an upper-middle income country by the World Bank and a newly industrialized country by several analysts. By 2050, Mexico could become the fifth or seventh largest economy. The country is considered both a power and middle power, and is often identified as an emerging global power. Due to its culture and history, Mexico ranks first in the Americas. Mexico is a country, ranking fourth in the world by biodiversity. In 2015 it was the 9th most visited country in the world, Mexico is a member of the United Nations, the World Trade Organization, the G8+5, the G20, the Uniting for Consensus and the Pacific Alliance. Mēxihco is the Nahuatl term for the heartland of the Aztec Empire, namely, the Valley of Mexico, and its people, the Mexica and this became the future State of Mexico as a division of New Spain prior to independence. It is generally considered to be a toponym for the valley became the primary ethnonym for the Aztec Triple Alliance as a result. After New Spain won independence from Spain, representatives decided to name the new country after its capital and this was founded in 1524 on top of the ancient Mexica capital of Mexico-Tenochtitlan
17.
John Flaxman
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John Flaxman R. A. was a British sculptor and draughtsman, and a leading figure in British and European Neoclassicism. Early in his career he worked as a modeller for Josiah Wedgwoods pottery and he spent several years in Rome, where he produced his first book illustrations. He was a maker of funerary monuments. His father, also named John, was known as a moulder and seller of plaster casts at the sign of the Golden Head, New Street, Covent Garden. His wifes maiden name was Lee, and they had two children, William and John, within six months of Johns birth the family returned to London. He was a child, high-shouldered, with a head too large for his body. His mother died when he was nine, and his father remarried and he had little schooling, and was largely self-educated. He took delight in drawing and modelling from his fathers stock-in-trade and his fathers customers helped him with books, advice, and later with commissions. Particularly significant were the painter George Romney, and a clergyman, Anthony Stephen Mathew. In the same year,1770, he entered the Academy as a student, in the competition for the gold medal of the Academy in 1772, however, Flaxman was defeated, the prize being awarded by the president, Sir Joshua Reynolds, to a competitor named Engleheart. This episode seemed to help cure Flaxman of a tendency to conceit which led Thomas Wedgwood V to say of him in 1775, It is and he continued to work diligently, both as a student and as an exhibitor at the Academy, with occasional attempts at painting. To the Academy he contributed a wax model of Neptune, four models in wax, a terracotta bust, a wax figure of a child, an historical figure, a figure of Comedy. During this period he received a commission from a friend of the Mathew family for a statue of Alexander the Great, but he was unable to obtain a regular income from private contracts. From 1775 he was employed by the potter Josiah Wedgwood and his partner Bentley, for whom his father had also some work. The usual procedure was to model the reliefs in wax on slate or glass grounds before they cast for production, dHancarvilles engravings of Sir William Hamiltons collection of ancient Greek vases were an important influence on his work. By 1780 Flaxman had also begun to earn money by sculpting grave monuments, during the rest of Flaxmans career memorial bas-reliefs of this type made up the bulk of his output, and are to be found in many churches throughout England. One example, the monument to George Steevens, originally in St Matthais Old Church, is now in the Fitzwilliam Museum, in 1782, aged 27, Flaxman married Anne Denman, who was to assist him throughout his career. She was well-educated, and a devoted companion and they set up house in Wardour Street, and usually spent their summer holidays as guests of the poet William Hayley, at Eartham in Sussex
18.
Cutting
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Cutting is the separation of a physical object, into two or more portions, through the application of an acutely directed force. Implements commonly used for cutting are the knife and saw, or in medicine and science the scalpel, however, any sufficiently sharp object is capable of cutting if it has a hardness sufficiently larger than the object being cut, and if it is applied with sufficient force. Even liquids can be used to cut things when applied with sufficient force, cutting is a compressive and shearing phenomenon, and occurs only when the total stress generated by the cutting implement exceeds the ultimate strength of the material of the object being cut. Hence, the smaller the area, the force is needed to cut something. It is generally seen that cutting edges are thinner for cutting soft materials and this progression is seen from kitchen knife, to cleaver, to axe, and is a balance between the easy cutting action of a thin blade vs strength and edge durability of a thicker blade. Cutting has been at the core of manufacturing throughout history, for metals many methods are used and can be grouped by the physical phenomenon used. Chip forming - sawing, drilling, milling, turning etc, abrading - grinding, lapping, polishing, water-jet. Heat - flame cutting, plasma cutting, laser cutting, electrochemical - etching, electrical discharge machining. Every method has its limitations in accuracy, cost, and effect on the material, for example, heat may damage the quality of heat treated alloys, and laser cutting is less suitable for highly reflective materials such as aluminum. Laser cutting sheet metal produces flat parts and etches and engraves parts from complex or simple designs and it is used over other cutting options for its quick process and customizable abilities
19.
Goldsmith
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A goldsmith is a metalworker who specializes in working with gold and other precious metals. Goldsmiths must be skilled in forming metal through filing, soldering, sawing, forging, casting, the trade has very often included jewellery-making skills, as well as the very similar skills of the silversmith. Many universities and junior colleges also offer goldsmithing, silversmithing, compared to other metals, gold is malleable, ductile, rare, and it is the only solid metallic element with a yellow color. It may easily be melted, fused, and cast without the problems of oxides and gas that are problematic with other such as bronzes. It is fairly easy to weld, wherein similarly to clay two small pieces may be pounded together to make one larger piece. Gold is classified as a noble metal—because it does not react with most elements and it usually is found in its native form, lasting indefinitely without oxidization and tarnishing. Gold has been worked by humans in all cultures where the metal is available, either indigenously or imported, and the history of these activities is extensive. Superbly made objects from the ancient cultures of Africa, Asia, Europe, India, North America, Mesoamerica, some pieces date back thousands of years and were made using many techniques that still are used by modern goldsmiths. Techniques developed by some of those goldsmiths achieved a level that was lost and remained beyond the skills of those who followed. In medieval Europe goldsmiths were organized into guilds and usually were one of the most important, the guild kept records of members and the marks they used on their products. These records, when they survive, are useful to historians. Goldsmiths often acted as bankers, since they dealt in gold and had sufficient security for the storage of valuable items. The Sunar caste is one of the oldest communities in goldsmithing in India, in India, Vishwakarma are the goldsmith caste. The printmaking technique of engraving developed among goldsmiths in Germany around 1430, the notable engravers of the fifteenth century were either goldsmiths, such as Master E. S. or the sons of goldsmiths, such as Martin Schongauer and Albrecht Dürer. A goldsmith might have an array of skills and knowledge at their disposal. Gold, being the most malleable metal of all, offers opportunities for the worker. In todays world a variety of other metals, especially platinum alloys. 24 Carat is pure gold and historically, was known as fine gold, because it is so soft, however,24 Carat gold is rarely used
20.
Florence
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Florence is the capital city of the Italian region of Tuscany and of the Metropolitan City of Florence. It is the most populous city in Tuscany, with 383,083 inhabitants, Florence was a centre of medieval European trade and finance and one of the wealthiest cities of the time. It is considered the birthplace of the Renaissance, and has called the Athens of the Middle Ages. A turbulent political history includes periods of rule by the powerful Medici family, from 1865 to 1871 the city was the capital of the recently established Kingdom of Italy. The Historic Centre of Florence attracts 13 million tourists each year and it was declared a World Heritage Site by UNESCO in 1982. The city is noted for its culture, Renaissance art and architecture, the city also contains numerous museums and art galleries, such as the Uffizi Gallery and the Palazzo Pitti, and still exerts an influence in the fields of art, culture and politics. Due to Florences artistic and architectural heritage, it has been ranked by Forbes as one of the most beautiful cities in the world, in 2008, the city had the 17th highest average income in Italy. Florence originated as a Roman city, and later, after a period as a flourishing trading and banking medieval commune. According to the Encyclopædia Britannica, it was politically, economically, and culturally one of the most important cities in Europe, the language spoken in the city during the 14th century was, and still is, accepted as the Italian language. Starting from the late Middle Ages, Florentine money—in the form of the gold florin—financed the development of all over Europe, from Britain to Bruges, to Lyon. Florentine bankers financed the English kings during the Hundred Years War and they similarly financed the papacy, including the construction of their provisional capital of Avignon and, after their return to Rome, the reconstruction and Renaissance embellishment of Rome. Florence was home to the Medici, one of European historys most important noble families, Lorenzo de Medici was considered a political and cultural mastermind of Italy in the late 15th century. Two members of the family were popes in the early 16th century, Leo X, catherine de Medici married king Henry II of France and, after his death in 1559, reigned as regent in France. Marie de Medici married Henry IV of France and gave birth to the future king Louis XIII, the Medici reigned as Grand Dukes of Tuscany, starting with Cosimo I de Medici in 1569 and ending with the death of Gian Gastone de Medici in 1737. The Etruscans initially formed in 200 BC the small settlement of Fiesole and it was built in the style of an army camp with the main streets, the cardo and the decumanus, intersecting at the present Piazza della Repubblica. Situated along the Via Cassia, the route between Rome and the north, and within the fertile valley of the Arno, the settlement quickly became an important commercial centre. Peace returned under Lombard rule in the 6th century, Florence was conquered by Charlemagne in 774 and became part of the Duchy of Tuscany, with Lucca as capital. The population began to again and commerce prospered
21.
Vitreous enamel
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Vitreous enamel, also called porcelain enamel, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C. The powder melts, flows, and then hardens to a smooth, durable vitreous coating on metal, so in technical terms fired enamelware is an integrated layered composite of glass and metal. Enamelling is an old and widely adopted technology, for most of its history mainly used in jewelry, enamelled and enamelling are the preferred spellings in British English, while enameled and enameling are preferred in American English. The term enamel is most often restricted to work on metal, enamelled glass is also called painted, and overglaze decoration to pottery is often called enamelling. The word enamel comes from the Old High German word smelzan via the Old French esmail, or from a Latin word smaltum, used as a noun, an enamel is usually a small decorative object coated with enamel. Since the 19th century the term also to industrial materials and many metal consumer objects, such as some cooking vessels, dishwashers, laundry machines, sinks. The ancient Egyptians applied enamels to stone objects, pottery, and sometimes jewellery, the ancient Greeks, Celts, Georgians, and Chinese also used enamel on metal objects. Enamel powder could be produced in two ways, either by powdering coloured glass, or by mixing colourless glass powder with pigments such as a metallic oxide, designs were either painted freehand or over the top of outline incisions, and the technique probably originated in metalworking. Once painted, enamelled glass vessels needed to be fired at a high enough to melt the applied powder. Ancient Persians used this method for colouring and ornamenting the surface of metals by fusing over it brilliant colours that are decorated in an intricate design and called it Meenakari. Gold has been used traditionally for Meenakari Jewellery as it holds the enamel better, lasts longer, initially, the work of Meenakari often went unnoticed as this art was traditionally used as a backing for the famous kundan or stone-studded jewellery. This also allowed the wearer to reverse the jewellery as also promised a special joy in the secret of the hidden design, the Byzantine enamel style was widely adopted by the barbarian peoples of Migration Period northern Europe. The Byzantines then began to use cloisonné more freely to create images, the champlevé technique was considerably easier and very widely practiced in the Romanesque period. In Gothic art the finest work is in basse-taille and ronde-bosse techniques, from either Byzantium or the Islamic world, the cloisonné technique reached China in the 13-14th centuries. The first written reference to cloisonné is in a book from 1388, cloisonné remained very popular in China until the 19th century and is still produced today. Starting from the century, the Japanese also produced large quantities of very high technical quality. A resurgence in enamel-based art took place near the end of the 20th century in the Soviet Union, led by artists like Alexei Maximov, in Australia, abstract artist Bernard Hesling brought the style into prominence with his variously sized steel plates. Enamel was first applied commercially to sheet iron and steel in Austria, industrialization increased as the purity of raw materials increased and costs decreased
22.
Silver
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Silver is a metallic element with symbol Ag and atomic number 47. The symbol Ag stems from Latin argentum, derived from the Greek ὰργὀς, a soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal is found in the Earths crust in the pure, free form, as an alloy with gold and other metals. Most silver is produced as a byproduct of copper, gold, lead, Silver is more abundant than gold, but it is much less abundant as a native metal. Its purity is measured on a per mille basis, a 94%-pure alloy is described as 0.940 fine. As one of the seven metals of antiquity, silver has had a role in most human cultures. Silver has long valued as a precious metal. Silver metal is used in many premodern monetary systems in bullion coins, Silver is used in numerous applications other than currency, such as solar panels, water filtration, jewelry, ornaments, high-value tableware and utensils, and as an investment medium. Silver is used industrially in electrical contacts and conductors, in specialized mirrors, window coatings, Silver compounds are used in photographic film and X-rays. Dilute silver nitrate solutions and other compounds are used as disinfectants and microbiocides, added to bandages and wound-dressings, catheters. Silver is similar in its physical and chemical properties to its two neighbours in group 11 of the periodic table, copper and gold. This distinctive electron configuration, with an electron in the highest occupied s subshell over a filled d subshell. Silver is a soft, ductile and malleable transition metal. Silver crystallizes in a cubic lattice with bulk coordination number 12. Unlike metals with incomplete d-shells, metallic bonds in silver are lacking a covalent character and are relatively weak and this observation explains the low hardness and high ductility of single crystals of silver. Silver has a brilliant white metallic luster that can take a polish. Protected silver has greater optical reflectivity than aluminium at all wavelengths longer than ~450 nm, at wavelengths shorter than 450 nm, silvers reflectivity is inferior to that of aluminium and drops to zero near 310 nm. The electrical conductivity of silver is the greatest of all metals, greater even than copper, during World War II in the US,13540 tons of silver were used in electromagnets for enriching uranium, mainly because of the wartime shortage of copper
23.
Lead
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Lead is a chemical element with atomic number 82 and symbol Pb. When freshly cut, it is bluish-white, it tarnishes to a dull gray upon exposure to air and it is a soft, malleable, and heavy metal with a density exceeding that of most common materials. Lead has the second-highest atomic number of the stable elements. Lead is a relatively unreactive post-transition metal and its weak metallic character is illustrated by its amphoteric nature and tendency to form covalent bonds. Compounds of lead are found in the +2 oxidation state. Exceptions are mostly limited to organolead compounds, like the lighter members of the group, lead exhibits a tendency to bond to itself, it can form chains, rings, and polyhedral structures. Lead is easily extracted from its ores and was known to people in Western Asia. A principal ore of lead, galena, often bears silver, Lead production declined after the fall of Rome and did not reach comparable levels again until the Industrial Revolution. Nowadays, global production of lead is about ten million tonnes annually, Lead has several properties that make it useful, high density, low melting point, ductility, and relative inertness to oxidation. In the late 19th century, lead was recognized as poisonous, Lead is a neurotoxin that accumulates in soft tissues and bones, damaging the nervous system and causing brain disorders and, in mammals, blood disorders. A lead atom has 82 electrons, arranged in a configuration of 4f145d106s26p2. The combined first and second ionization energies—the total energy required to remove the two 6p electrons—is close to that of tin, leads upper neighbor in group 14. This is unusual since ionization energies generally fall going down a group as an elements outer electrons become more distant from the nucleus, the similarity is caused by the lanthanide contraction—the decrease in element radii from lanthanum to lutetium, and the relatively small radii of the elements after hafnium. The contraction is due to shielding of the nucleus by the lanthanide 4f electrons. The combined first four ionization energies of lead exceed those of tin, for this reason lead, unlike tin, mostly forms compounds in which it has an oxidation state of +2, rather than +4. Relativistic effects, which become particularly prominent at the bottom of the periodic table, as a result, the 6s electrons of lead become reluctant to participate in bonding, a phenomenon called the inert pair effect. A related outcome is that the distance between nearest atoms in crystalline lead is unusually long, the lighter group 14 elements form stable or metastable allotropes having the tetrahedrally coordinated and covalently bonded diamond cubic structure. The energy levels of their outer s- and p-orbitals are close enough to allow mixing into four hybrid sp3 orbitals
24.
Sulfur
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Sulfur or sulphur is a chemical element with symbol S and atomic number 16. It is abundant, multivalent, and nonmetallic, under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a yellow crystalline solid at room temperature. Chemically, sulfur reacts with all elements except for gold, platinum, iridium, tellurium, though sometimes found in pure, native form, sulfur usually occurs as sulfide and sulfate minerals. Being abundant in native form, sulfur was known in ancient times, being mentioned for its uses in ancient India, ancient Greece, China, in the Bible, sulfur is called brimstone. Today, almost all elemental sulfur is produced as a byproduct of removing sulfur-containing contaminants from natural gas, the greatest commercial use of the element is the production of sulfuric acid for sulfate and phosphate fertilizers, and other chemical processes. The element sulfur is used in matches, insecticides, and fungicides, many sulfur compounds are odoriferous, and the smells of odorized natural gas, skunk scent, grapefruit, and garlic are due to organosulfur compounds. Hydrogen sulfide gives the characteristic odor to rotting eggs and other biological processes, sulfur is an essential element for all life, but almost always in the form of organosulfur compounds or metal sulfides. Three amino acids and two vitamins are organosulfur compounds, many cofactors also contain sulfur including glutathione and thioredoxin and iron–sulfur proteins. Disulfides, S–S bonds, confer mechanical strength and insolubility of the keratin, found in outer skin, hair. Sulfur is one of the chemical elements needed for biochemical functioning and is an elemental macronutrient for all organisms. Sulfur is derived from the Latin word sulpur, which was Hellenized to sulphur, the spelling sulfur appears toward the end of the Classical period. In 12th-century Anglo-French, it was sulfre, in the 14th century the Latin ph was restored, for sulphre, the parallel f~ph spellings continued in Britain until the 19th century, when the word was standardized as sulphur. Sulfur was the form chosen in the United States, whereas Canada uses both, the IUPAC adopted the spelling sulfur in 1990, as did the Nomenclature Committee of the Royal Society of Chemistry in 1992, restoring the spelling sulfur to Britain. Sulfur forms polyatomic molecules with different chemical formulas, the best-known allotrope being octasulfur, cyclo-S8. The point group of cyclo-S8 is D4d and its dipole moment is 0 D. Octasulfur is a soft, bright-yellow solid that is odorless and it melts at 115.21 °C, boils at 444.6 °C and sublimes easily. At 95.2 °C, below its melting temperature, cyclo-octasulfur changes from α-octasulfur to the β-polymorph, the structure of the S8 ring is virtually unchanged by this phase change, which affects the intermolecular interactions. At higher temperatures, the viscosity decreases as depolymerization occurs, molten sulfur assumes a dark red color above 200 °C
Chisholm, Hugh, ed. (1911). "Line engraving". Encyclopædia Britannica. 16 (11th ed.). Cambridge University Press. pp. 721–4.
Chisholm, Hugh, ed. (1911).