Repairing a cracked or shattered window pane is an easy repair, especially if the broken pane is relatively small.For large panes or dual glazing (or other high-performance glass), it’s usually smarter to call a glass dealer. In most cases, a special pane will have to be ordered—you will want to have the replacement on hand before your remove the old pane.

The first thing to do is remove the broken glass. Tape the cracked pane with a cross-hatch of duct tape to prevent glass shards from falling out as you work. Be sure to wear safety glasses and heavy gloves when working with glass.

When replacing a window pane, try to buy the same kind of glass originally installed in the window so it will match the glass in the other panes or other windows in the room (this may not always be possible if you have an older home). Take a shard to your hardwarestore and ask your dealer to match any coatings or other features.

Also pad the glass with newspaper when you take it to or from the store. Dispose of fragments in your regular trash; window glass usually can’t be recycled.

After removing the broken glass, chisel out the old putty (if it’s hard, you may need to soak it with linseed oil or soften it with a heat gun). Remove the old glazier’s points with long-nose pliers. Clean and sand the wood, and coat it with wood sealer.

To replace glass secured with rubber seals

Unscrew the two sash halves and remove the inside one. Brush out glass fragments, set a new pane against one sash half, replace the other half of the sash, and secure the sash parts with screws.

If the glass sits on a continuous rubber gasket 

Remove the screws from a vertical end of the sash, and pull the end away from the sash. Clean out the old glass, and then pull the gasket around the new pane; slide the pane into the sash, and secure the end.

To replace glass in a sash with snap-out moldings

Loosen one end of a piece of molding by inserting the tip of a putty knife where two ends meet. Pry gently, using the frame for leverage. Pull out the loosened strip of molding. When you have replaced the pane, push each molding piece into place with your hands. Pieces damaged during removal should be replaced.