Stained and Coloured Glass
Stained glass can refer to coloured glass as a material or to works created from it – most commonly seen in the stained glass windows of churches and other buildings. Coloured glass is also found in everyday life such as green wine bottles.
As a material stained glass is glass that has been coloured by adding metallic salts during its manufacture.
There are two main types of glass – soda lime glass – commonly used in beverage bottles and the like and borosilicate glass – used in laboratory glassware and also some domestic glassware such as oven proof dishes.
Coloured glass is made in a number of ways. There are three main ways.
The first involves introducing metallic or rare earth metal oxides to the glass as mentioned above.
Silver compounds for example such as silver nitrate are used as stain applied to the surface of glass and fired on. They can produce a range of colours from orange-red to yellow. The way the glass is heated and cooled can significantly affect the colours produced by these compounds.
Another way is by formation of colloidal particles. This means particles of a substance are suspended throughout the glass. The particles scatter light of particular frequencies as it passes through the glass, causing colouration.
Gold gives a ruby red colour, and selenium gives a pink to intense red.
The final main way in which colour can be introduced is through the addition of already coloured particles to the glass. Examples of this type of colouration include milk glass and smoked glass; milk glass is achieved by adding tin oxide.
The infographic below from Compound Interest shows what chemicals are involved in the colour process. Click for a larger image.
|Click to enlarge|
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