If you break a window and cannot get replacement glass immediately, as a temporary measure fix a sheet of polythene to the inside of the window. With a wood frame either fix the polythene with adhesive tape or, for a stronger fixing, secure the top of the polythene to the window with drawing pins, nail a batten along the top and then secure each side and bottom edge with battens. Stretch the polythene to smooth out wrinkles as you work. Use heavy duty polythene secured with strong adhesive tape for a metal frame.
Wood frames
Clear up the glass left on the ground and remove the fragments in the frame. These should pull away easily; you may have to remove the holding material. Take out the glass from the top of the frame, then work down the sides and along the bottom edge. To remove stubborn pieces run a glass-cutter round the perimeter of the glass and close to the rebates. Tap out the pieces with the handle of a light hammer, holding each piece until it is free. If the holding material is putty chop away with a hacking knife or old chisel. This will reveal a series of small headless nails (sprigs) which do the real job of holding the glass. Carefully remove the sprigs with pincers. If they are still straight, you can re-use them; if not, buy new ones 16mm long. Sometimes the glass will have been secured by wood beading fixed with panel pins. Prise away the beading and remove the pins. Take care when removing since the beading will have mitred ends to form neat corner joints and if you damage these you will have to buy more beading and shape the mitres yourself.
Brush out all the dust from the rebates and rub the timber smooth with medium coarse glasspaper. Apply a coat of wood primer and leave to dry.
Measuring up
Accurate measuring for the new sheet of glass is vital. Measure the full width of the opening between the side rebates at the top, centre and bottom of the frame. These should be the same, but if there is a slight difference work on the smallest measurement. Next measure between the other two rebates, top to bottom, again if necessary noting the smallest measurements. Deduct 3mm from these dimensions (this is to allow for the glass expanding and contracting in the frame). These are the dimensions to use when ordering your glass. If your window frame is badly out of square or an awkward shape, such as curved, make a template (pattern) of the frame from card or stiff paper so the glass can be cut to the exact size. For normal domestic use you will need 3mm sheet glass. Take some old newspapers to wrap round the glass or wear gloves to protect your hands from the edges when carrying it.
Fitting the glass
Hold the new glass up to the frame to check it is the right size. Knead some linseed oil putty into a ball in your hands to make it soft and pliable and if necessary add a little linseed oil to make the putty more workable. (Putty has an irritating habit of clinging to dry surfaces when you do not want it to, so keep both hands and the putty knife wet.) Run a continuous layer of putty about 3mm thick round the rebates and press well in with your thumb. Carefully lift the glass into position, allowing for the 3mm expansion gap, and press it into the layer of putty pushing only on the edge of the glass, never in the middle. Refit the sprigs, spacing them at intervals of about 150mm around the glass. They must be flat against the glass to hold it securely, so tap them in carefully. The flat edge of a wide chisel could be used for this. Run another layer of putty around the front of the glass, pressing it in with your thumb. With a putty knife smooth out the layer, shaping it to match the angle on your other windows, and form mitres at the corners . Use the edge of the knife to trim off surplus putty from the glass.