Glass and Glazing

Window glass is sold by the square foot or, in large quantities, by the 100 square feet. Its thickness is indicated by its weight in ounces per square foot. For small panes 15-ounce glass, about fg inch thick, may be used; for large panes it should be 21-ounce, or about -fo inch thick. Where panes are large, and great strength is needed, 26-ounce glass is recommended.

The use of glass of this last gauge in sash windows makes the use of very heavy weights and very strong cords necessary.

Clearing the Rebate

The first step in replacing a broken pane is to remove the old putty thoroughly from the rebate. This operation is usually carried out with a hacking knife, struck on the back with a light hammer to break the putty away from the glass and wood with its tip. An old chisel, ground to an angle of 45°, is useful for removing the front putty.

If the putty is first softened by running a hot iron or soldering bit over it, the putty can be cut away very easily without damaging the sash. But care must be taken not to scorch the wood. Clear away all old putty, cleaning well into the angles, as any left may prevent the new pane being bedded in properly or may cause cracking .

New windows should have the rebates veil primed with red lead paint before being puttied, and old ones will be all the better for a coat.

When the rebates are clear, measure for the new pane. This must be inch smaller in both directions than the opening, to give room for putty between glass and wood all round the edges. A properly inserted pane touches wood nowhere.

A supply of putty should be obtained at the same time as the glass; also a few brads, or zinc glaziers points, for holding the glass in place while the final putty is added.

Applying the Putty

Then press the glass gently into the putty, taking care that it is properly centred, with putty all round it, especially at the bottom.

Work round and round till the glass has tumk evenly into the rebate everywhere and squeezed out putty at all points at the back . The glass is then prevented from being pushed outwards again by any elasticity in the putty by a couple of brads or points along each side, touching the glass, driven into the wood far enough not to project through the front putty when it is applied. While driving, keep the hammer up against the glass.

Making a neat job of the front putty requires some practice, but skill is soon acquired. The putty is laid on by hand all round as evenly as possible, and then smoothed by drawing the putty knife slowly along, with one side pressing on the edge of the rebate, and its point touching the glass.

Do not allow the putty to force the knife out of contact; and hold the knife flat enough to prevent its rear corner roughing the putty. The front putty should not be visible from the inside of the window, so keep its inner edge well within the rebate.

The first attempts may not be very successful. In some places the putty may have been torn away from wood or glass, and in others show hollows, missed by the knife. It must then be gone over again, after a little putty has been added here and there. The corners give most troubla. Finish them with strokes approaching from both directions.

Any excess putty on the glass separated by the knifes tip is brushed off, and that at the back cut off neatly by drawing the knife along the wood. Any hollows in the back putty should be carefully filled in.

Next day, paint the front putty over with a paint matching that on the frame. Besides concealing the putty, the paint prevents it cracking, and helps seal the joint. It should extend to the glass everywhere, but not be carried far enough on to it to be unsightly from the back. So the brush must be used carefully.

Any putty left over should be pressed down into a jam-pot and covered with water, which is protected against evaporation by a piece of glass or wood laid on the top of the pot. Stored in this way, putty will keep soft indefinitely, though it hardens quickly if exposed to air. Hard putty need not, however, be thrown away, as it may be softened by heating and working up in the hands, after the addition of a few drops of linseed – not lubricating – oil.