lass is any substance or mixture of substances that has solidified from the liquid state without crystallization.
Glass may be defined as a hard, transparent or translucent (allowing light, but not detailed images, to pass through) material chiefly compound of silica, combined with varying proportions of oxides of sodium, potassium, calcium, magnesia, iron, and other minerals.
Structure of glass: The glass is a random arrangement of molecules, the great majority of which are oxygen ions bounded together with the network forming ions of silicon, boron or phosphorous.
Glass
Obtained from fusion of silica, chalk (lime) and potash or soda at over 1000°C
Silica – main constituent which fuses at high temperature so alkaline admixture added to lower down fusion temperature
Potash – gives fire resistant properties to glass
Soda – quickens fusion of glass
Lime – imparts durability and toughness
Lead oxide – provides color
Cullet – broken glass of the type to be made to bring down cost of production
Properties of glass
No definite crystalline structure
No sharp melting point
Absorbs, refracts or transmits light
Affected by alkalies
Extremely brittle
Available in beautiful colors
Not affected by water or air
(substance or compound that is added to a system in order to bring about a chemical reaction or is added to see if a reaction occurs)
Glass Manufacturing
All constituents separately ground, sieved and mixed in definite proportions
Mix fused in tank furnace or pot furnace
Charge fed at one end and molten glass tapped at other end continuously
Molten glass shaped by following methods
Blowing – articles of various shapes by blowing pipe
Flat drawing – plate of glass pressed between rollers to form sheet glass
Rolling – molten glass poured over flat iron table rolled into sheet
Compression molding – irregular shape articles using molds
Spinning – glass fibers produced by spinning action
Soda lime glass
Fusion of silica, lime, soda and alumina mixture.
Also called soda-ash glass, soda glass or soft glass.
Used for glazing doors, windows, common glassware
Lead glass
Fusion of silica, lead and potash
Also called flint glass
Boro-silicate glass
Fusion of silica, borax, lime and feldspar
Withstands high temperature
Lab equipment and cookware made with it
Sheet glass
Ordinary glazing quality – general glazing
Selected glazing quality – better quality work
Special selected quality – show cases and cabinets
Available in thickness of 2.0 to 12.0 mm
Plate glass
Ground and polished
Available in thickness of 3.0 to 32.0 mm
GG quality – cabinets, show cases, shelves, counters, etc
SG quality – mirrors
SQ quality – superior quality for high class work
Tempered plate glass
Glass plate is heated and suddenly cooled to give it a temper
Much stronger than ordinary glass
Laminated Glass
Used for glazing windows and doors of buildings and land transport
Wired glass
translucent glass with special steel wire mesh embedded between layers of glass during manufacture
Fire retardant and provides safety
Special annealing process gives additional resistance to breakage
Used where light and safety are both required
Insulating glass
Two or more glass layers with 6 to 12 mm intervening layers of dehydrated air hermetically sealed
Used for glazing windows and doors of buildings where heat insulation and light transmission are both needed
Colored glass
Various metal oxides are added to molten glass to provide desired color
Used for decoration work in buildings
Heat absorbing glass
Glass of bluish green tinge that cuts off ultra violet rays of sun
Flint glass
Lead glass which shines and takes up polish
Used for cut glass work, as optical glass, electric bulbs,, etc
Ground glass
One face of sheet glass made rough and translucent by grinding
Used for privacy
Block glass
Hollow sealed glass blocks of various sizes
Squares, ribs, flutes, prisms, etc cast as such
Used to provide heat and sound proof partitions
Bullet poof Glass
Steps For EFFLORESCENCE test
NIL – When there is not perceptible deposit of efflorescence. (b) SLIGHT- Not more than 10% area of the brick covered with a thin deposit of salt. (c) MODERATE- Covering upto 50% area of the brick. (d) HEAVY- Covering 50% or more but unaccompanied by powdering or flacking of the brick surface. (e) SERIOUS- When, there is a heavy deposit of salts accompanied by powdering and/or flacking of the exposed surfaces.
REMEDIES FOR EFFLORESCENCE: 1. Well fired bricks should be used in construction. 2. Sand should be tested for its salt content. 3. Proper D.P.C. should be provided in the building. 4. Efflorescence on brick work traceable to salts in the materials can be removed by dry brushing and washing repeatedly. Such efflorescence may re-appear in dry season but usually are less
Miscellaneous Clay Products
Terracotta. Ornamental, impervious, hard clay
Porous terracotta. Clay plus sawdust or cork
Polished terracotta. Glazed architectural clay
Porcelain. High grade, white, zero water absorption and glazed material of clay, kaolin, quartz and feldspar
Soft porcelain
Hard porcelain
Stoneware. Colored porcelain with silica and alumina. Flooring tiles
Earthenware. Drain pipes, lavatory fittings, light partition walls
Majolica. Italian earthenware coated with opaque white enamel, ornamented with metallic colors
Glazing
Transparent glazing. Sodium chloride used while burning
Lead glazing. Burned items dipped in lead oxide solution
Opaque glazing. Borax, kaolin, chalk, color, feldspar and lead oxide fired. Resulting molten glass poured in water to give shattered look
