Now a days, the world market is flourishing with several new types of pigments that are used for coloring the glass equipments. In past, the various kind of impurities were responsible for producing colors in the glass equipments. For example, in the 17th century, in the 'black bottle glasses', the color dark brown or green was found due to the present of iron impurities. These impurities came in these glasses from two sources. One, and was used to make these glasses and second, sulphur from the smoke of the burning coal was used for melting these glasses.
But, today, the glass is colored by using various kinds of pigments (Purified metal salts). Some ancient examples of colored glass are: ruby glass (gold chloride is used as a pigment, invented in 1679), uranium glass (uranium oxide is oxide as a pigment, invented in the year 1830). It doesn't mean that, for every time, the colored glasses are useful. Sometimes, we need such glass, which is free from any color. At that time, we have to removed the unwanted color from the glass. The process of removing the color is called as Decolorizing process. Some commonly used decolorizing agents are: Manganese dioxide and Cerium Oxide.
Special Effects in Glasses By Using Pigments Special color effect can be generated in the glasses by using some pigments either individually or in the combined form with other types of pigments. For example, Iridescent glass (Iris glass) has a special coloring effect. This coloring effect in the iris glass can be generated by adding some metallic compounds (pigments). Sometimes, the coloring effect, in the iris glass can be generated by spraying its surface with lead chloride and then heating it in the present of reducing agent. Another colored glass is Dichroic glass. From different angles, the color in the glass seems to be changed. This is happened because, a very thin layer of colloidal metals (gold or silver) is applied on the surface of the glass.
Some pigments and their coloring effects in glass
|Name of Pigment Compounds||Coloring Effects|
|Iron Oxide||Green, Brown|
|Manganese Oxides||Deep Amber, Amethyst, Decolorizer|
|Cobalt Oxide||Deep Blue|
|Gold Chloride||Ruby Red|
|Mix of Manganese, Cobalt, Iron Black, Antimony Oxide||White|
|Uranium Oxides||Glowing Yellow-Green|
|Copper Compounds||Light Blue, Red|
|Lead with Antimony||Yellow|
Some Usable Pigments in Glass Industry
Sodium Pigments are also used as a decolorizing agents in the glass industry. These pigments are used as a refining agents.
Nickel Inorganics Pigments
Nickel Inorganic Pigments are used to add colors, enhance the strength in the end glass products, and some other features in the glass products.
Cobalt Inorganics Pigments
Cobalt inorganic pigments are used in various applications. These applications vary from adding colors, increasing strength to produce finished glass products.
Antimony Trioxide (Sb2O3)
These pigments are also known as White Pigments. These pigments are used in the glass industry as decolorizing agents. To remove the unwanted colors from the glasses, these pigments can be used. There purification capacity is very high and free from all types of impurities.
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