What Is Glass?
This part of our web site illustrates the many applications that Glass has in our Society. To satisfy the curiosity of those interested in learning more about the material and the industries based on it, there is a further information section at the end, giving useful web links. We hope this will extend over time.
The term 'glass' refers to a state of matter, usually produced when a viscous molten material is cooled rapidly to below its glass transition temperature, with insufficient time for a regular crystal lattice to form. Consequently a key feature is that glasses have structures that are liquid-like i.e. not crystalline; this means that they lack the internal structural boundaries present in most other materials. So they are typically transparent to light, although this can also depend on their composition. As a result they are enormously valuable for windows, containers, ovenware, tableware, lighting, and optical fibres for telecommunications (underpinning the internet and mobile phones).
The picture shows Bent Flat Glass in Modern Architecture, Museum of History, Berlin (Architect I.M. Pei)
The most familiar chemical forms of glass are the silica-based materials used for architectural and automotive glazings, containers, table glassware, glass wool for heat insulation and decorative objects. These compositions have a high viscosity in the molten state which:
- aids glass formation, as the constituent ions can only re-arrange themselves with difficulty,
- and makes possible fabrication into a multitude of shapes as the melt is cooled.
Such materials allow the aerodynamic design of car windshields whilst giving the driver an undistorted image. The windows are variously laminated or toughened to protect the occupants in the event of a crash, and can be coated or even coloured to control heat gain, to prevent UV damaging the seals and for special effects including augmented reality such as navigational aids.
An area in which glasses are playing a vital role is in reducing the world’s carbon footprint. For example this picture shows the parabolic glass mirrors (silver coated) of a solar thermal power plant in the Mojave Desert, California capable of generating 350 MW.
But glasses can be made from many different compositions using a wide variety of processes to give products with an even wider range of properties and applications than found for silica based systems. These are less familiar but form the basis for a wide range of speciality glasses such as optical materials, laboratory glass, cooktop panels, display screens, glass fibers for reinforcement of plastics, amplifiers, multiplexers and switches for optical fibre telecommunication systems.
These days techniques such as laser structuring are able to modify a glass surface on an amazingly fine scale. This picture, for example, shows a planar diffractive microlens with a diameter of just 0.6 mm .
Glasses will dissolve a wide variety of different materials such as the oxides of chromium, cobalt, copper, iron, manganese and nickel to produce a rainbow of colours. Each element of the coloured components in this Medieval Stained Glass Window (11th Century, Augsburg, Germany) consists of an individually produced coloured glass sheet cut to the required shape any held in place by lead cames. In this window enamelling with black stain was used to add fine detail.
Later people learned how to use silver stains to produce local areas on clear sheets that were coloured yellow or orange. This same basic technology of ion exchange is now used to strengthen fine objects such as wine glasses and to produce thin channels in the surface of glass sheets that can guide light, just as optical fibres do.
To find out more about the artistic aspects of stained glass have a look at the following web site, which also contains numerous additional links: http://www.affordablelamps.com/stained-glass-fixtures-learn-more.html
Have you ever thought what would the world be like without glass? From buildings to appliances, from furniture to electronic devices, flat glass is omnipresent in our daily life. Windows, cars, mobile phones and tablets, photovoltaic panels...
Corning report an antimicrobial version of their Gorilla Glass.
For the latest on TV in a contact lens click here.
For new researchers from academia or industry our annual Summer School may be interest (6-10th July 2015). Go to the link Montpellier summer school for details of the 2014 event. 2015 will see two streams in parallel one devoted to Glass Science and the other to Coating technologies.
Web based teaching material is available at: http://www.lehigh.edu/imi/