GLASS

• Density : 24.3 KN/m3
• Burning temperature : 1400 - 1500*C 
• Natural type of glass : rock crystals 
• Glass is formed by the solidification of molten metallic silicates 
• Glass is a solidified super cooled liquid of various metals having infinite viscosity 
• glass is transparent and good insulator due to the absence of free electron

TYPES OF GLASS 

Soda lime glass 
• Soft glass / commercial glass 
• Sodium silicate + calcium silicate 
• Fuses at low temp 
• Available in pure state 
• Used in pipette, burette 

 Potash lime glass 
• Hard glass / bohemian glass 
• Potassium silicate + calcium silicate 
• Fuses at high temp 
• Used in glass articles which withstand high temperature 

Potash lead glass 
• Flint glass 
• Potassium silicate + lead silicate 
• Fuses very easily 
• Becomes black and opaque in contact with furnace gas 
• Used in lens, prism, gems 

Common glass 
• Bottle glass 
• Sodium silicate + calcium silicates + iron silicates 
• Does not fuse easily 
• Easily affected by acid 
• Used in medicine bottle 
• Brown, green, yellow 

Boro silicate glass
• Pyrax 
• 70 - 80 % silica 
• 7 - 13% boric acid 
• Small amount of alkalis & iron oxide 
• High chemical stability 
• Thermal shock resistant 
• Used in chemical industry, laboratory apparatus, glass fiber

SPECIAL VARIETIES OF GLASS 

1. ALKALI BARIUM SILICATE GLASS : used in TV to filter X rays 

2. ALUMINO SILICATE GLASS 
• 20 % aluminum , remaining silica 
• Can withstand high temperature 
• Used in combustion tube & steal boilers 

3. BULLET PROOF GLASS 
• Several layers of plain glass and vinyl resin plastic is used 
• Thickness of glass : 15 - 75 mm 

4. FIBER GLASS 
• Flexible 
• Fire proof, water proof 
• Used in communication tech 

5. FLOAT GLASS 
• Molten glass allowed to float on molten tin 
• Used in residential, commercial, furniture articles etc 

6. FOAM GLASS 
• Finely ground carbon & glass 
• Thermal insulator 
• Floats on water 
• Used in AC, refrigerator 

7. GLASS BLOCK / BUILDING BLOCK : square building blocks of size 150 x 200 x 300 mm 

8. LEAD CRYSTAL GLASS 
• High lecture 
• Used for making glasswires 

9. HEAT EXCLUDING GLASS ( anti actinic ) 
• Excludes uv rays , infrared rays 
• Used in railway coaches , buildings 

10. PERFORATED GLASS : used in panels of ventilators 

11. GLASS CERAMIC 
• Formed from lithium alumino silicate glass 
• Extremely resistant to thermal shocks 
• Used in cooking wares, missile nose etc. 

12 PATTERNED GLASS / OBSCURED GLASS 
• Transmits light but obstructs vision 

13. PHOTO CHROMATIC GLASS 
• Temporary darkens when exposed to sunlight 
• Silver bromide is present 

14. OPTICAL GLASS : used in specs, micro scopes 

15. SAFETY GLASS / SHATTER PROOF GLASS : celluloid sheets are placed between glass 

16. SEALING GLASS : used for sealing electrical components 

17. SHIELDING GLASS : shields against radiation 

18. SILICA GLASS : bromo silicate variety ( porous type is called vycor glass ) 

19. STRUCTURAL GLASS / GLASS CRETE 
• Square shaped glass reinforced with steel frames 
• Used in partition, lantern lights 

20. SOLUBLE GLASS : soluble in water , used in making acid resistant concrete 

21. UV RAY GLASS 
• Transmits uv rays 
• Used in windows of schools, hospitals etc. 

22. WIRED GLASS 
• Wire mesh is placed during rolling 
• Fire resistant, does not break easily 
• Used in roof, skylights etc.


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