Constituents Of glass:
Na2O, CaO, K2O, PbO, B2O3, Fe2O3
Raw Materials:
Sodium as (Na2CO3)
Potassium as K2CO3
Calcium as Limestone, Chalk etc
Lead as litharge or red lead.
Silica as Quartz
Zinc as Zno
Borate as borax or borix acid.
Cullets (broken glass pieces to increase fusibility)
Colours (e.g. Yellow-ferric Salt, Purple - Manganese dioxide)
Manufacturing Steps:
- Melting
- Forming & Shaping
- Annealing
- Finishing
1:- Melting:
i) Pot furnace: a) Regeneretive
b) Recuperative
ii) Tank Furnace: a) Regenerative
b) Recuperative
The reactions taking places are given bellow-
For soda Glass : (Batch Na2CO3, CaCO3,SiO2)
Na2CO3 + SiO2 - - > Na2SiO3 + CO2
CaCO3 - - > CaO + CO2
CaO + SiO2 - - > CaSiO3
Na2CO3 + CaCO3 + 5SiO2 - - > Na2O.CaO.6SiO2 + 2CO2
Flint Glass: (Batch – Pb3O4, K2CO3.Sio2)
Pb3O4 - - > 3PbO + O
PbO + SiO2 - - > PbSiO3
K2CO3 + SiO2 - - > K2SiO3 + CO2
2:- Shaping: Moltan glass is moduled to desired shapes.
3:- Annealing: The process of slow cooling of glass articles to reduce the strain is known as annealing.
4: Finishing: Cutting, Polishing, Coloring, shaping etc.
