Presently, in the world market of glass, several
types of pigments are used for coloring the glass equipments. Earlier
glasses did not derived the colors from the pigments. At that time, 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.
Effects in Glasses By Using Pigments
By using some pigments either individually or in the
combined form with other types of pigments, special color effect can be
generated in the glasses. 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 stannous chloride or 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.
pigments and their coloring effects in glass
|Name of Pigment Compounds
||Deep Amber, Amethyst, Decolorizer
|Mix of Manganese, Cobalt, Iron Black, Antimony Oxide
||Light Blue, Red
|Lead with Antimony
Usable Pigments in Glass Industry
Cobalt Inorganics Pigments
Cobalt inorganic pigments are used in various applications. These
applications vary from adding colors, increasing strength to produce
finished glass products.
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
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. These
pigments purification capacity is very high and free from all types of
Sodium Pigments are also used as a decolorizing agents in the glass
industry. These pigments are used as a refining agents.