Always wear thick gloves and safety goggles when reglazing or repairing a damaged window containing broken glass. A broken window is both a security risk and a safety hazard.
Using putty
Putty is a pliable material which provides a waterproof bedding for the glass in the frame. When
putty is exposed to the air, it hardens during the first few weeks. If you need putty for metal
frames, ask for metal-casement putty, as linseed oil putty does not bond to metal.
There is also
a dual-purpose putty available which is suitable for both types of frames. Measure the dimensions
of the frame in order to know how much putty to buy. Putty does not keep for very long before
becoming too hard to use. Check the weight on the tub, but as a general rule, approximately:
1 foot length needs 4.5 ounces equivalent to 300mm length needs 125 grams
5 feet length needs 22.5 ounces equivalent to 1.5m length needs 625 grams
8 feet length needs 35 ounces (just over 2 lb) equivalent to 2.4m needs 1 kg
Mould the putty, by kneading a palm sized ball in your hands until it becomes pliable and does
not contain any lumps. If the putty is too difficult to mould into shape, use a little linseed
oil to soften. If, on the other hand, the putty is too sticky, wrap it in newspaper to remove
some of the excess oil. It should be possible to roll it smoothly into long cylinders-sausages.
Press the putty into the rebates all round, judging a sufficient thickness to bed the glass in,
and spread to the edges of the rebate.
Self-adhesive plastic foam
Alternatively, instead of using bedding putty, there is a self-adhesive plastic foam available
which can be used. This is applied all round the back of the rebate. Try to use it as a continuous
strip, start applying at the top and take it all round the frame. Place the glass into position
and press all round the edge, not in the centre of the pane. Check that there is a thin bed of
putty between the glass and the inside of the frame. Secure the glass with sprigs before
continuing with ordinary putty as with normal method.
Replacing the pane of glass
Press in the glass, by working with the fingers around the edges. Do not press at the centre of
the glass. Remember that the point where it is bedded down on the putty will be visible, so try
to get an even thickness behind it. Tap in sprigs in the case of a wooden frame or fit wire clips
if the frame is metal. Space the sprigs along the edges approximately 20cm (8 inches) apart. The
sprigs do not have to go in very far and may be tapped in by sliding the edge of a chisel or a
light hammer across some card over the glass.
More putty can be added from the outside with the fingers, but it will have to be pressed in
and smoothed with a putty knife. One with a diagonal cut across its end is suitable. Try to angle
the putty outside, to an angle of approximately 45° - making a triangular fillet, as this will
help the rain to run away from the frame in wet weather.
Press the putty down so that it bonds with that already in the rebate and draw the knife along so
the surface is beveled to come just below the rebate seen through the other side. If the putty sticks to
the knife wet the blade first. Use the straight edge of the knife to make neat mitres at the corners.
Surplus putty can be cut away with the knife from both sides of the glass.
Wipe around the putty lightly with a damp brush and leave the putty to harden for about at least
a week. Clean the glass with methylated spirit and paint over the putty and the frame. Carrying
the paint line a very short distance onto the glass will create a weather seal which will prevent
water getting behind the putty and loosening it.
Window Frames
Wood expands and contracts according to its moisture content and this depends on the weather for
outside woodwork. Wooden window frames set in brick may develop gaps where water has entered and
this causes rot. Do not fill these cracks with concrete, mortar or putty, as these set hard and
do not allow movement.
Buy a mastic sealer from a builders' merchant - see Builders Merchants. This may come in a tube, so that you squeeze the
sealer through its nozzle, or it may be in a gun with a lever action. Squeeze this into the gaps.
If necessary, press further with a putty knife, which should be kept wet to prevent sticking. The
mastic will set sufficiently hard to take the paint, but it remains elastic so that gaps will not
form.
