When you think of glass, windows and doors come to mind, but truth be told, glass is being used in so various forms and compositions for numerous purposes these days. By itself, glass is non-crystalline, transparent and generally very brittle. The transparency is due to the lack of grain boundaries which also results in easy cracking of the structure. Their non-crystalline nature also means they are referred to as amorphous or vitreous in nature.
In order to create a stronger form of glass, the tempered glass was created which is treated glass and has increased thermal durability and shock resistance and breaks comfortably into small pieces to reduce damage. These are usually used in cars and as fireplace guards.
Then we have the glass ceramic material which is created by re-heating of amorphous glass through a crystallization phase such that there is ‘controlled crystallization’. They differ from normal glass by being 90-95% crystalline in volume, with the remaining percentage usually being vitreous in nature.
And by virtue of its crystalline nature and good network of grain boundaries, glass ceramics are no longer transparent and have very small crystals that are uniform in size. This material is typically characterized by having high strength and durability, high impact resistance and a low co-efficient of thermal expansion; this basically means it’s not a good heat conductor and can withstand quick temperature changes. It also means it’s resistant to thermal shocks too. However it’s not totally unbreakable as it has elements of glass and ceramic. Glass ceramic also has a range of optical properties with its being translucent, opaque or even opalescence; it can also be colored with coloring agents for a more pleasing effect.
Glass ceramics are commonly used in making kitchen utensils as well as cook tops of stoves – both electrical and gas. The surface of a glass ceramic stove does not heat up; even when the heat is on, the adjacent areas are still cool as they are poor heat conductors. Glass ceramics are also used in induction cookers, where only the metal bottom of the pot gets hot through direct electromagnetic induction. So even while your pot is bubbling with food, the surface of the induction cooker remains cool – such are the miracles of modern science!
However, it’s not only in the kitchen that glass ceramic is useful as its also being used to manufacture other things too including telescopic mirrors, insulators and various engineering components also.