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Glass coloring and color marking may be obtained by 1) addition of ''coloring ions'',〔〔 by 2) precipitation of nanometer sized colloides (so-called ''striking glasses''〔Bernard H. W. S. De Jong, Ruud G. C. Beerkens, Peter A. van Nijnatten: "Glass", in: "Ullmann's Encyclopedia of Industrial Chemistry"; Wiley-VCH Verlag GmbH & Co. KGaA, 2002, 〕 such as "gold ruby"〔(Formation of Gold Nanoparticles in Gold Ruby Glass: The influence of Tin )〕 or red "selenium ruby"),〔Werner Vogel: "Glass Chemistry"; Springer-Verlag Berlin and Heidelberg GmbH & Co. K; 2nd revised edition (November 1994), ISBN 3-540-57572-3〕 3) by ''colored inclusions'' (as in milk glass and smoked glass), 4) by ''light scattering'' (as in phase separated glass),〔 5) by ''dichroic coatings'' (see dichroic glass), or 6) by ''colored coatings''. ==Coloring ions== Ordinary soda-lime glass appears colorless to the naked eye when it is thin, although iron oxide impurities produce a green tint which can be viewed in thick pieces or with the aid of scientific instruments. Further metals and metal oxides can be added to glass during its manufacture to change its color which can enhance its aesthetic appeal. Examples of these additives are listed below: * Iron(II) oxide may be added to glass resulting in bluish-green glass which is frequently used in beer bottles. Together with chromium it gives a richer green color, used for wine bottles. * Sulfur, together with carbon and iron salts, is used to form iron polysulfides and produce amber glass ranging from yellowish to almost black. In borosilicate glasses rich in boron, sulfur imparts a blue color. With calcium it yields a deep yellow color.〔(Substances Used in the Making of Coloured Glass ) 1st-glass.1st-things.com (David M Issitt). Retrieved 9 April 2014〕 * Manganese can be added in small amounts to remove the green tint given by iron, or in higher concentrations to give glass an amethyst color. Manganese is one of the oldest glass additives, and purple manganese glass was used since early Egyptian history. * Manganese dioxide, which is black, is used to remove the green color from the glass; in a very slow process this is converted to sodium permanganate, a dark purple compound. In New England some houses built more than 300 years ago have window glass which is lightly tinted violet because of this chemical change; and such glass panes are prized as antiques. This process is widely confused with the formation of "desert amethyst glass", in which glass exposed to desert sunshine with a high ultraviolet component develops a delicate violet tint. Details of the process and the composition of the glass vary and so do the results, because it is not a simple matter to obtain or produce properly controlled specimens. * Small concentrations of cobalt (0.025 to 0.1%) yield blue glass. The best results are achieved when using glass containing potash. Very small amounts can be used for decolorizing. * 2 to 3% of copper oxide produces a turquoise color. * Nickel, depending on the concentration, produces blue, or violet, or even black glass. Lead crystal with added nickel acquires purplish color. Nickel together with a small amount of cobalt was used for decolorizing of lead glass. * Chromium is a very powerful colorizing agent, yielding dark green〔(Chemical Fact Sheet - Chromium ) www.speclab.com. Retrieved 3 August 2006〕 or in higher concentrations even black color. Together with tin oxide and arsenic it yields emerald green glass. Chromium aventurine, in which aventurescence was achieved by growth of large parallel chromium(III) oxide plates during cooling, was also made from glass with added chromium oxide in amount above its solubility limit in glass. * Cadmium together with sulphur forms cadmium sulfide and results in deep yellow color, often used in glazes. However, cadmium is toxic. Together with selenium and sulphur it yields shades of bright red and orange. * Adding titanium produces yellowish-brown glass. Titanium, rarely used on its own, is more often employed to intensify and brighten other colorizing additives. * Uranium (0.1 to 2%) can be added to give glass a fluorescent yellow or green color.〔(Uranium Glass ) www.glassassociation.org.uk (Barrie Skelcher). Retrieved 3 August 2006〕 Uranium glass is typically not radioactive enough to be dangerous, but if ground into a powder, such as by polishing with sandpaper, and inhaled, it can be carcinogenic. When used with lead glass with very high proportion of lead, produces a deep red color. * Didymium gives green color (used in UV filters) or lilac red.〔 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「Glass coloring and color marking」の詳細全文を読む スポンサード リンク
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