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Silvering is the chemical process of coating glass with a reflective substance. When glass mirrors first gained widespread usage in Europe during the 16th century, most were silvered with an amalgam of tin and mercury,〔Kathleen Payne de Chavez. Historic Mercury Amalgam Mirrors: History, Safety and Preservation Spring 2010. http://www.williamstownart.org/techbulletins/images/WACC%20Historic%20Mercury%20Mirrors.pdf |accessdate= 11 March 2014〕 but by the 19th century mirrors were commonly made through a process by which silver was coated onto a glass surface. Today, sputtering aluminium or other compounds are more often used for this purpose, although the process may either maintain the name "silvering" or be referred to as aluminising. == History == The earliest mirrors were made from polished obsidian during the Stone Age,. By the Bronze Age most cultures had adopted mirrors made from polished discs of bronze, copper or other metals.〔 Such metal mirrors remained the norm through to Greco-Roman Antiquity and throughout the Middle Ages in Europe.〔(【引用サイトリンク】title=A Brief History of Mirrors )〕 It was not until the 1st century CE that glass mirrors began to show up, now believed to have originated in Sidon, in what is modern-day Lebanon. In Ptolemaic Egypt small glass mirrors were made backed by lead, tin, or antimony.〔 In the early 10th century, the Persian scientist al-Razi described ways of silvering and gilding in a book on alchemy, but this was not done for the purpose of making mirrors. In 1835 German chemist Justus von Liebig developed a process for depositing silvering on the rear surface of a piece of glass that gained wide acceptance after improvement by Liebig in 1856. The process was further refined and made easier by French chemist Petitjean (1857). This reaction is a variation of the Tollens' reagent for aldehydes. A diamminesilver(I) solution is mixed with a sugar and sprayed onto the glass surface. The sugar is oxidized by silver(I), which is itself reduced to silver(0), i.e. elemental silver, and deposited onto the glass. In 1856-57 Karl August von Steinheil and Léon Foucault introduced the process of depositing an ultra thin layer of silver on front surface of a piece of glass, making the first optical quality first surface glass mirrors, replacing the use of speculum metal mirrors in reflecting telescopes.〔(Mazing-space.stsci.edu - Era of Huge Reflectors )〕 These techniques soon became standard for technical equipment. An aluminum vacuum-deposition process invented in 1930 by Caltech physicist and astronomer John Strong, led to most reflecting telescopes shifting to aluminum.〔("Mirror, Mirror: Keeping the Hale Telescope optically sharp" ) by Jim Destefani, ''Products Finishing Magazine'', 2008〕 Nevertheless, some modern telescopes use silver, such as the Kepler space observatory. The ''Kepler'' mirror's silver was deposited using ion assisted evaporation.〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「silvering」の詳細全文を読む スポンサード リンク
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