Types of glasses:
Crown glass
It is the cheapest quality of glass, used for window panes of small sizes, bottles, electric bulbs, etc.
Sheet glass
For all general engineering purposes the glass used is sheet glass.
Sheet glass is manufactured in thickness of:
2, 2.5, 3.0, 4.0, 5.0, 5.5 and 6.5 mm.
Glass window panes shall be not less than 2 mm thick for panes up to 30 x 30 cm size and 3 mm thick for panes bigger than 30 x 30 cm.
For size above 90 cm use plate glass 6 mm thick or above.
There should be a space of 1.5 mm all round the panes between the edges of the glass and the rebate; a cushion of rubber, felt, or canvas may be given in between to absorb shocks.
Plate glass
It is stronger than sheet glass and also more transparent. Is manufactured in sheets varying from 3/16 in. to 1 in.(usual thickness are 3mm to 32mm). plate glass is superior to sheet glass and is used for large size glass panes for shop fronts, windscreens of motor cars and looking glasses etc.
Wired glass
Wire-netting is embedded in plated glass during rolling. It resists fire better than plate glass, and in case of fracture, the glass does not fall to pieces.
Safety glass or Shatter-proof glass
This is either (i) toughened variety of glass, or (ii) reinforced with wire-mesh, or (iii) a combination of two glass sheets between which a layer of transparent celluloid or any other transparent plastic is sandwitched.
Glass-crete
Glass-crete are small square pieces of glass which are set in steel frames or concrete, for light in the basements. Semi-prisms are made on the underside of the glass pieces which collect light and project it into the basement.
Flint glass or lead glass
Flint glass or lead glass is used for are glass, cut glassware, ratio valves, lenses etc. This glass is clearer than other type of glass and takes a finer polish.
Pyrex glass
Pyrex glass is a proprietory brand of heat resisting glass which is used for making cooking utensils, electric insulators and laboratory apparatus etc.
Anti-actinic or Heat Excluding glass
These glasses when used in windows resist heat passing through without affecting the normal passage of light. Are commonly used for railway coaches.
Rendeing Panes of glass Opaque
White lead 1/2kg. linseed oil 12 grams, varnish 30 grams, mix the whole till becomes plastic. The mixture is applied by tying it up in a piece of linen into balls about 25mm dia. And pressing these balls against the glass with force (i.e tapping). They should not be rubbed over the glass as, if this is done, streaks make their appearance. Ordinary zinc white paint also produces good results when applied with a ball of silk cloth.
Galzier’s putty
Glass panes are secured in place by means of putty or wooden moulds. Rebates should be painted or oiled one coat before glazing. Galzier’s prigs or brads are fixed 75 to 150 mm apart. Rebates should be at least 12 mm.
Putty is made by mixing one part of white lead with three parts of finely powdered chalk and then adding boiled linseed oil to the mixture, to form a stiff paste, which is well kneaded and left for 12 hours covered with a wet cloth and finally worked up in small pieces. A little of varnish is sometimes added to the paste. Quantity of putty is 185 grams per metre of glass perimeter. For glazing in metal lashes, 5 percent red lead should be added. Litharge is sometimes added as a drier. (whiting is absolutely dead stone lime or finally powdered chalk). In metal sashes, 4 glazing clips may be provided per glass pane for a size 30 cm x 60 cm, where glass panes exceed 80 cm x 200 cm, 6 glazing clip are used. Holes for glazing clips have to be dritted prior to fabrication.
Glass panes can be cleaned by
a. Methylated spirit
b. Painting the glass panes with lime wash and leaving it to dry and then washing with clean water
c. Rubbing finally powered chalk
d. Rubbing damp salt for cleaning paint spots
