This section is from the book "A Practical Treatise On The Joints Made And Used By Builders", by Wyvill J. Christy. Also available from Amazon: Practical treatise on the joints made and used by builders.
Under this head may be named the device for enabling condensed water to run off from the interior of stone windows in churches, chapels, and public rooms. A piece of lead is dressed down over the sill, as shown in Fig. 161, under each light, in a sinking made for it, and the glass is bedded in the grooves so as to leave an opening of about ⅛ in. between its bottom edge and the surface of the lead. Overlapping Joint. - This is another term for lap joint.
All joints made with lead putty or oil cement should be painted, to prevent the oil evaporating, and the edges of sheet-glass require to be painted black before bedding. All wooden sash bars, likewise, must be primed or painted before the squares are stopped in.
After the woodwork is primed the glass is bedded in putty, which is made of four degrees of hardness, but that generally used is a mixture of whiting, white lead, and boiled linseed oil. There is no universal rule as to the composition of the so-called soft, hard, very hard, and hardest putty. The addition of flour or olive oil makes it softer, and so does the omission of white lead and the substitution of raw for boiled oil. White or red lead, sand, and turps add to its hardness: 7 per cent, of tallow conduces to its continued pliability. In glazing, the back putty is first laid on the rebate to bed the square upon, but this is sometimes omitted both with the best and worst descriptions of glass, but never in work of fair quality. After well pressing the square upon the back putty, the stopping is completed with the front putty, which is run along the edge of the rebate and finished off with a bevelled surface in a direction away from the glass. The front putty is usually on the outside and exposed to the weather, excepting in the case of shop windows, which are glazed from the inside for security.
This appellation is especially applicable to those joints now employed on a large scale on extensive roofs, which are formed by slipping the glass into grooves to be retained in place by clips, with or without the pressure of india-rubber attached to a capping on the bars. A contrivance in the shape of small gutters in the vertical bars or perforations in the horizontal ones is provided to allow condensed vapour to run off from the inside. Bundle's "acme" system of glazing without putty can be used with iron bars, thereby dispensing with wood, and presenting peculiar and advantageous features for flat exposed roofs. Fletcher's patent "metal substitute" also gives a secure fixing to glass as well as a neat appearance to roofing without the use of putty.
S-Joint is formed in skylights when the panes overlap and the tail of one pane is connected with the head of another by means of an S-shaped clip.
When the panes are large and heavy the joints between them and the bars are often first sprigged with iron or copper brads or sprigs, which have no heads, and afterwards front-puttied with common or red-lead putty.
Thermo-plastic Putty Joint is formed by adding tallow to glaziers' putty, to enable it to become plastic by the heat of the sun and firm again upon cooling, which quality renders it suitable for securing large panes of glass without the risk of their becoming loose through expansion and contraction.
Wash-leather Joint is made in glazing when large squares in sash-doors, etc, are stopped with plate-glass, in order to lessen the injurious effects of slamming or other sudden concussion. A strip of wash-leather is glued to the inside of the rebate, and another to the inside edge of the bead screwed to the frame or bar to hold the pane in its place. Previous to insertion the edges of the glass must be painted black.