Civil Engg. Subjects 
Materials Engineering 
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Civil Related LinksMANUFACTURE OF GLASS
All the constituents of glass are separately ground, sieved and mixed in desired proportions. The mix is then fused in a tank furnace or in a pot furnace. The former is used for large scale productions and later for smaller productions of superior quality. The charge that is fed at one end of the furnace is continuously taped in molten state at the other end. The molten glass is given the desired shape by any one of the following methods.-
Blowing:
- The operator dip one end of a blow pipe ( 12mm in dia. and 2 m long) in the molten glass and takes it out
- The blow pipe is held vertically on taken it out after a dip
- The sticking molten glass lengthens
- Then the molten glass is blown vigorously the molten glass takes the shape of a hollow ball
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Flat drawing:
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Iron rod is dipped into the molten glass and moved sideways to form a plate of glass which is then passed in rollers to form glass sheets.
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Rolling:
The molten glass is poured over flat iron table which has rollers fixed at one edge. The molten glass is rolled into sheet of glass.
CLASSIFICATION
Glass is usually classified into three main classes
- Soda lime glass
- It is obtained from the fusion of a mixture of silica, lime, soda and alumina.
- Powdered glass too may be added
- This glass is also termed as Soda-ash glass, Soda glass or Soft glass
- It is used for glazing doors, windows and making ordinary glass wares
- Lead glass:
- It is obtained from the fusion of a mixture of silica, lead and potash
- Powdered glass too may be added
- This glass is also termed as Flint glass
- Lead glass has highly shining appearance
- It is not affected by temperature
- Cut glass work, electric bulbs and optical glass are made from it
- Boro-silicate glass:
- It is obtained from the fusion of a mixture of silica, borax, lime, and feldspar.
- Powdered glass too may be added
- This glass withstands high temperature
- Laboratory equipments and kitchen utensils are made out of it
COMMERCIAL FORMS
Glass is marketed in various commercial forms to suit varying field requirements.
- Sheet Glass:
- Most extensively used in engineering works
- Size ► Thickness of 2, 2.5, 3, 4, 5 5.5 and 6.5 mm► sheets up to 175 cm x 110 cm sizes are also available
Ordinary glazing quality: Used for general glazing
Selected glazing quality: Used for better quality works
Special selected quality: Used for superior quality works such as show cases etc
- Plate glass:
- It is made in thickness varying from 3mm to 32 mm and sizes up to 275cm x 90cmm.
- It is stronger and more transparent than the sheet glass
- Tempered plate glass:
- Glass plate is heated and then suddenly cooled to tamper it
- Tempered glass is much stronger than ordinary sheet glass.
- Used for glazing entrance doors, table tops, shelves, counters etc
- Laminated glass:
- Two or more glass plates with intervening layers of transparent plastics are bound under effect of heat and pressure.
- This type of glass is not broken into pieces when it breaks
- Ensures safety at places where glass is liable to shatter
- Glazing windows and doors
- Wired glass:
- It is a rough cast translucent (semi transparent) glass with special steel wire mesh of 0.46 to 0.56 mm dia.
- Wire mesh completely embedded between the layers of glass during manufacture process
- Fire resistant and safe during breakage
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Insulating glass:
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Two layers of glass separated by 6mm to 12mm of air space are sealed to provide heat insulation
- Colored glass:
- By adding oxides of metals to metal glass the finish product get colored
- Used for decoration works in building construction
- Flint glass:
- It is lead glass which shines
- Used for glass work as optical glass, for making electric bulbs.
