This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol2", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
The effect of fire is similar to that on plate glass; but, while the plate glass falls out and is dangerous, the wired glass, although cracked, remains in position. The renewals of wired glass are more expensive than those of plate.
Glass Slates and Tiles are useful where a small amount of light is required. They are made of rough rolled plate 1/8, 3/10, 1/4, and 3/8 inch in thickness, and secured to the battens with wooden pegs or copper clips.
Putty is made from raw linseed oil, and whiting ground to a fine powder. The oil is added to the whiting, and the mixture kneaded into a stiff paste and left for twelve hours, when it is afterwards worked up in small pieces till quite smooth.
Where the rebate is small a little white or red lead may be added to make the putty more adhesive.
Soft putty is made as follows:-10 lbs. of whiting and 1 lb. of white lead are mixed with a half gill of the best salad oil, and an admixture of linseed oil to bring it to the proper consistency.
Thermoplastic putty is similar to that stated above, with the addition of tallow, which makes it pliable, so that it will stand the expansion of large panes of glass.
In glazing in wooden sashes or frames, care should be taken that the glass is cut slightly less than the distance between the rebates. These are back puttied, i.e. a layer of putty is spread over the narrow part of the rebate, and on this the glass is bedded. The remaining part of the rebate is stopped by a triangular piece of putty which holds the glass in position.
The waste putty squeezed out by the glass should not be cut off for at least a week after the glass has been stopped in. Large sheets should be sprigged in addition.
Plate glass in doors, and other places where it is liable to concussion, is frequently bedded on vulcanised indiarubber, or washleather, one piece of which is glued to the inside of the rebate and the other placed on the reverse side of the glass. It is maintained by some that this becomes hard, owing to the weather or moisture, and that the glass cracks, but on examination it will probably be found, in such a case, that in fixing the beads a screw has been placed too near the edge of the glass, which causes it to fracture.
In large skylights where there are no transverse bars the glass has to overlap. In that case the two sheets should be hung together with copper clips. The slope of the roof will govern the lap, but as a general rule 1 1/2 inch will be found sufficient.
The woodwork to be glazed should be first primed to assist the adhesion of the putty (if putty is used), or the glass is secured by wood fillets in rebates without putty, and the rebates are placed inside instead of out. Brass screws and cups should be used, and a little lead putty for the bedding.
This system of glazing without putty is now extensively used for large factory, station, and conservatory roofs. There are many systems in use at the present time, each of which claims some special advantage.
A successful system should have the following characteristics:-
1. Simplicity of construction, enabling it to be easily repaired, and broken glass replaced by ordinary workmen.
2. It should possess sufficient strength to permit of workmen crawling over it to execute repairs.
3. It should allow of the expansion and contraction of the roof (if iron) without breaking the glass.
4. The sash bars should not be so heavy as to materially obstruct the light.
5. Metal parts and fastenings should be so arranged as to protect them from corrosion from the weather.
The following illustrations show some of the systems at present in use:-
This patent glazing is used for greenhouses, conservatories, and small skylights, and consists of fixing strips of lead nailed to wooden bars. The bars should be about 15 inches apart centre to centre, with a flat top from 1 1/2 to 1 3/4 inch wide, and grooved as shown.
The lead strips are fastened down the centre of the rafter, leaving the grooves clear, and are secured to same with 3/4-inch copper tacks 8-inch pitch (4 inches apart on alternate sides of the flange). Where the glazing is on movable parts the nailing should be half that distance. For thick glass, and where the roof is steep, copper clips should be used at the foot of each pane.
Fig. 228 shows the various sections of the bars and their application and fitting.
Hope's Glazing has been largely used for railway stations. Fig. 229 shows a section of the bar.
The lead is cast to the shape indicated, and fitted into the groove in the top of bar, being afterwards turned down on to the glass. It will be noticed that condensation channels of ample width are provided.
Rendle's "Invincible" Glazing has also been extensively used, especially for railway station roofs. Fig. 230 shows the method of fixing. For lengths up to 4 feet, the bar as shown in black, either in copper or zinc, can be used. For lengths above 4 feet, wood bars, or steel tees, as shown by dotted lines, must be used.
Mellow's "Eclipse" Glazing. - Fig. 231 shows the various bars and fixings. The bars may be either of wood or steel, the fixing of the glass being a tinned lead metal cover, soldered at both ends. It is claimed that no breakage of glass from expansion and contraction can take place.