22-12-2012, 11:12 AM
GLASS
GLASS.ppt (Size: 2.24 MB / Downloads: 43)
It is a mixture of number of metallic silicates, one of which is usually that of an alkali metal.
It is amorphous, transparent and translucent.
It may also be considered as a solidified, super-cooled solution of various metallic silicates having infinite viscosity.
It is an inorganic solid material that is usually clear or translucent with different colors. It is hard, brittle, and stands up to the effects of wind, rain or sun.
Thermal and sound insulating properties are two of its most important properties .
DISCOVERY OF GLASS:
Natural glass has existed since the beginnings of time, formed when certain types of rocks melt as a result of high-temperature phenomena such as volcanic eruptions, lightning strikes or the impact of meteorites, and then cool and solidify rapidly.
Stone-age man is believed to have used cutting tools made of obsidian (a natural glass of volcanic origin also known as hyalopsite, Iceland agate, or mountain mahogany) and tektites (naturally-formed glasses of extraterrestrial or other origin, also referred to as obsidianites).
According to the ancient-Roman historian Pliny (AD 23-79), Phoenician merchants transporting stone actually discovered glass (or rather became aware of its existence accidentally) in the region of Syria around 5000 BC.
Pliny tells how the merchants, after landing, rested cooking pots on blocks of nitrate placed by their fire. With the intense heat of the fire, the blocks eventually melted and mixed with the sand of the beach to form an opaque liquid.
This brief history looks, however, at the origins and evolution of man-made glass.
PROPERTIES OF GLASS
MAIN CHARACTERISTICS OF GLASS:
- It is a Solid and hard material
- It Has a Disordered and amorphous structure
- Fragile and easily breakable into sharp pieces
- Transparent to visible light
- It is inert and biologically inactive material.
Glass is 100% recyclable and one of the safest packaging materials due to its composition and properties
Glass is used for architecture application, illumination, electrical transmission, instruments for scientific research, optical instruments, domestic tools and even textiles.
Glass does not deteriorate, corrode, stain or fade and therefore it is one of the safest packaging materials.
Glass is a very good thermal as well as sound insulating material.
SODA GLASS :
It is the cheapest & most common glass. It is prepared by fusing soda ash, sand and limestone. It is also called soft glass. It fuses at comparatively low temperatures. The major disadvantage of using this glass is that it is brittle & breaks easily. It cracks when subjected to sudden changes of temperature it is used for the manufacture of window glass, mirrors, common glassware etc. It is easily attacked by chemicals.
HARD GLASS :
It is obtained by fusing potassium carbonate & limestone. It is used for making hard glass apparatus. It is more resistant to the action of acids.
FLOAT GLASS :
It is a sheet of glass made by floating molten glass on a bed of molten tin.
This method gives the sheet uniform thickness and very flat surfaces.
Modern windows are made from float glass.
It is widely used for residential buildings, commercial complexes, furniture articles etc.
GLASS.ppt (Size: 2.24 MB / Downloads: 43)
It is a mixture of number of metallic silicates, one of which is usually that of an alkali metal.
It is amorphous, transparent and translucent.
It may also be considered as a solidified, super-cooled solution of various metallic silicates having infinite viscosity.
It is an inorganic solid material that is usually clear or translucent with different colors. It is hard, brittle, and stands up to the effects of wind, rain or sun.
Thermal and sound insulating properties are two of its most important properties .
DISCOVERY OF GLASS:
Natural glass has existed since the beginnings of time, formed when certain types of rocks melt as a result of high-temperature phenomena such as volcanic eruptions, lightning strikes or the impact of meteorites, and then cool and solidify rapidly.
Stone-age man is believed to have used cutting tools made of obsidian (a natural glass of volcanic origin also known as hyalopsite, Iceland agate, or mountain mahogany) and tektites (naturally-formed glasses of extraterrestrial or other origin, also referred to as obsidianites).
According to the ancient-Roman historian Pliny (AD 23-79), Phoenician merchants transporting stone actually discovered glass (or rather became aware of its existence accidentally) in the region of Syria around 5000 BC.
Pliny tells how the merchants, after landing, rested cooking pots on blocks of nitrate placed by their fire. With the intense heat of the fire, the blocks eventually melted and mixed with the sand of the beach to form an opaque liquid.
This brief history looks, however, at the origins and evolution of man-made glass.
PROPERTIES OF GLASS
MAIN CHARACTERISTICS OF GLASS:
- It is a Solid and hard material
- It Has a Disordered and amorphous structure
- Fragile and easily breakable into sharp pieces
- Transparent to visible light
- It is inert and biologically inactive material.
Glass is 100% recyclable and one of the safest packaging materials due to its composition and properties
Glass is used for architecture application, illumination, electrical transmission, instruments for scientific research, optical instruments, domestic tools and even textiles.
Glass does not deteriorate, corrode, stain or fade and therefore it is one of the safest packaging materials.
Glass is a very good thermal as well as sound insulating material.
SODA GLASS :
It is the cheapest & most common glass. It is prepared by fusing soda ash, sand and limestone. It is also called soft glass. It fuses at comparatively low temperatures. The major disadvantage of using this glass is that it is brittle & breaks easily. It cracks when subjected to sudden changes of temperature it is used for the manufacture of window glass, mirrors, common glassware etc. It is easily attacked by chemicals.
HARD GLASS :
It is obtained by fusing potassium carbonate & limestone. It is used for making hard glass apparatus. It is more resistant to the action of acids.
FLOAT GLASS :
It is a sheet of glass made by floating molten glass on a bed of molten tin.
This method gives the sheet uniform thickness and very flat surfaces.
Modern windows are made from float glass.
It is widely used for residential buildings, commercial complexes, furniture articles etc.