The Colour of Glass

Transition metal Modern raw material Colouring ion Colour in tetrahedral coordination (network former) Colour in octahedral coordination (network modifier) 

Cobalt Cobalt(III) oxide Co203 1 Co11 Blue Pink 

Manganese Manganese(IV) oxide Mn02 Mn11 Colourless to faint yellow, Weak orange, red fluorescence 

Iron Iron(II) oxalate Fe(C204).2H20 Fe11 - Absorbs in infrared 

Uranium Uranium oxide U3Og UVI Yellowish orange Weak yellow, green 

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The transmission and absorption values should be related to particular w avelengths. A plot of transmittance or absorption coefficient in terms of wavelength yields characteristic curves that can be used for describing quantitatively the colouring of glass (see Chapter II, Section 6.6 on coloured glasses). 

Smalt or Powder Blue. A fused mixture of cobalt oxide, sand and a flux, e.g. potash. It is sometimes used as a blue pigment for the decoration of pottery or for the colouring of glass or vitreous enamel (cf. zaffre). 

Bromine. Slip slightly to one side the glass plate covering one jar of ethylene, add 2-3 ml. of bromine water (preparation, p. 525), restore the glass plate in position, and then shake the jar vigorously. The colour of the bromine rapidly disappears as 1,2-dibromoethanc is formed. Note that owing to the absorption... 

W. A. Weyl, Coloured Glasses The Society of Glass Technology, Sheffield, UK, 1951, p. 179. 

Note. A 250 mL graduated flask with a short neck and a well-fitting ground-glass stopper may also be used. The colour of the organic layer is readily seen by inverting the flask so that the layer of solvent indicator collects in the neck. 

Figure 2. The colour of metallic gold and of gold nanoparticles in ruby glass.

In the modern world, we are accustomed to taking the chemical stability of glass very much for granted - we rely on the durability of glass for so many things, such as windows and (until the widespread availability of plastics) bottles, as well as its use in the chemical laboratory as an extremely inert and unreactive container. In addition to its apparent inertness, glass has a number of other beneficial properties, such as its transparency or the ability to take on virtually any colour as the result of the addition of a small amount of transition metals. 

It is clear that the colour of a glass is the result of a complex interplay between the co-ordination of the transition metal ions, the redox reactions between the various ions present and the redox potential in the furnace. The traditional archaeological view that colour can be simply related to the presence of various colouring agents can only be regarded as a very crude guide. 

It is possible to make the colour of a cholesteric LC independent of temperature by locking it covalently into a polymer matrix. This can be achieved by cross-linking parts of the sample at different temperatures or by quenching locally at temperatures below the glass transition temperature. 

Ware and Glass Makers, to give a blue Colour to both Sorts of Ware, Tis also with Safre that they colour calcin d Pewter, in order to make the false Stone, which I ve noted in the Chapter of Enamels And lastly, with Safre it is that the azure Colour of Glass is produc d, as is before observ d, and of which is made the counterfeit Sapphires (117). 

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