Tools and materials
Screwdriver, small hammer, pliers, spatula, small headless nails, glass cutter, chisel, strips of wood, putty or silicon. And don't forget the safety goggles and gloves.Setting a pane of glass in a wood-frame window used to be done with special putty that hardened with time. It is now outdated. The most common technique is to set them with silicon and, for a more decorative touch, wooden strips that you can later paint or leave their natural color.

 

Removing the old glass
If it is broken or you simply want to replace the existing pane, you have to remove the old one. If the former case, remove all the glass the remains in the frame. Do it by hand, wearing heavy gloves, or with pliers. Remove the wooden strip with a chisel or the tip of a screwdriver. If the pane was set in place with putty or silicon, use the chisel and hammer to clean the groove fully until you hit wood.

 

Taking measurements
Measure the surface, both height and width, and order glass a few millimeters smaller (2 mm per side should be enough) so later you won't have trouble getting the pane of glass into the frame or to compensate for the wood expanding. As a precaution measure the frame in several spots because there can be miniscule differences that will affect how the pane fits in. Be careful with old windows because the mullions and crosspieces may not be exactly parallel. Calculate possible irregularities before buying the new glass or cutting glass and do a test fitting.

 

Cutting
You can avoid this by having the glass shop do it for you, in the size, texture, color and thickness you want. If you do want to do the cutting yourself, place the glass on a totally flat board that you have covered with felt or some similar material. This way the glass will be less likely to slide around. With a felt-tipped pen mark the lines along which you want to cut, and with a T-square to guide pass the blade of the glasscutter along those lines. Make just one, firm cut. Use a yardstick or bar long enough for this purpose. If you have no experience in this, practice on a piece of glass you are going to throw away, or on the broken one you are replacing. Sliding part of the glass off the edge of the board, gently tap upward with the handle of the glasscutter. Or, with the yardstick underneath, press with both hands until the glass separates along the line. Smooth away jagged points or rough edges with the pliers.

 

Putting the new pane of glass in
With the edges of the frame good and clean (don't forget to remove old nails), insert the new pane of glass, making sure it does not fall. If you want, beforehand apply a string of silicon that will help you set the window in place and serve as insulation. Place the wooden strips in place again, knocking the nails in parallel to the glass. Use a claw hammer for headless nails so they are not visible.

 

Most important of all
You must be very careful when nailing in the wooden strip. This is the most important part of the job. Even a slight blow can break the pane. Also make sure the nails do not graze the glass. You can use a glasscutter's hammer, which are small and have fine points, but a cabinetmaker's hammer should do, as long as you hammer parallel to the glass. You will find that if you graze it, the glass does not break easily. But it can crack with a single perpendicular blow. As a general rule, the larger the windowpane, the thicker the glass should be, assuming the window frame can accommodate it.