All About Glass
Modern life just would not be possible without glass. From the jar that holds the morning marmalade, the mirror in which we brush our teeth, the windows and car windscreen we look through, the computer screens, smartphones and tablets many of us use at work everyday, the communications infrastructure to the light bulb we switch off last thing at night; glass is around us everywhere.
But, what is this amazing substance, where does it come from and how is it made?
What is glass?
Glass is a combination of sand and other minerals that are melted together at very high temperatures to form a material that is ideal for a wide range of uses from packaging and construction to fibre optics. A form of glass occurs naturally within the mouth of a volcano when the intense heat of an eruption melts sand to form Obsidian, a hard black glassy type of stone. Man first used this as tips for spears. Today man has mastered the glass-making process and can make many different types of glass in infinitely varied colours formed into a wide range of products. Glass, chemically, is actually more like a liquid, but at room temperature it is so viscous or sticky it looks and feels like a solid. At higher temperatures glass gradually becomes softer and more like a liquid. It is this latter property, which allows glass to be poured, blown, pressed and moulded into such a variety of shapes.
How is glass made?
Glass is made by melting together several minerals at very high temperatures. Silica in the form of sand is the main ingredient and this is combined with soda ash and limestone and melted in a furnace at temperatures of 1700°C. Other materials can be added to produce different colours or properties. Glass can also be coated, heat-treated, engraved or decorated. Whilst still molten, glass can be manipulated to form packaging, car windscreens, glazing or numerous other products. Depending on the end use, the composition of the glass and the rate at which it is allowed to cool will vary, as these two factors are crucial in obtaining the properties the glassmaker is seeking to achieve.
What are the different types of glass?
Glasses may be devised to meet almost any imaginable requirement - there are many different types of glass with different chemical and physical properties and each can be made by a suitable adjustment to chemical compositions. For many specialised applications in chemistry, pharmacy, the electrical and electronics industries, optics, the construction and lighting industries, glass, or the comparatively new family of materials known as glass ceramics, may be the only practical material for the engineer to use.
Glass is 100% recyclable and can be recycled an infinite number of times without quality, strength and/or functionality degradation.
In this Section
The oldest examples of glass are Egyptian beads dating from 12,000 BC.