Replacing a broken pane is not difficult. Just measure the opening and buy a piece of glass cut 1/8 inch smaller in width and length. You’ll also need work gloves, a chisel, a heat gun or hair dryer, pliers, boiled linseed oil, a putty knife, glazing compound (also called window putty), and metal glazing points with extending “ears.”
1. Wearing gloves, carefully remove the broken glass.
Then use a chisel to chip out all the old compound around the
opening, being careful not to damage the wood. Use a hair dryer or
heat gun to soften stubborn chunks. As you work, pull out the original metal glazing points with pliers.
2. Coat the exposed wood in the opening with linseed oil
and let it soak in well. Then line the opening with a thin bead of
compound, and press the new piece of glass into place.
3. Use a putty knife to push new glazing points into place
against the glass every 4 inches around the perimeter. Don’t use
the old holes.
4. Apply more compound over the glazing points and around
the exposed edges of the glass, occasionally dipping the putty
knife in linseed oil to keep it from sticking to the compound. Let the
compound cure for about a week before repainting.