How to Fix a Cracked Window in a Metal Frame

Spread a drop cloth or old sheet out just below the window. Use a putty knife or box cutter to cut into the putty surrounding the cracked glass to free the glass in one piece. If the glass shatters, remove it manually one shard at a time.

Remove any remaining putty from the frame using your putty knife or box cutter to scrape the putty free. Avoid digging into the metal or gouging the surface. Blow hot air over the putty with a heat gun or hair dryer, if needed, just ahead of where you are working with the putty knife to remove stubborn pieces.

Slip the corner of your putty knife under the spring clips as they become exposed from under the putty. Remove the clips without bending them and set them aside for later.

Measure the pane space along the inside of the metal frame in height and width. Don’t measure just the open space or your glass will not be large enough to rest inside the frame. Have a piece of glass cut to the size needed at your local home improvement center.

Apply a thin 1/16-inch layer of putty to the inside surface of the frame where the glass will touch. Hold the glass pane to the opening and position it in the frame. Press the glass into the putty to hold it secure. Set at least two spring clips removed earlier along each side and push the clips into place with the putty knife.

Work a relatively dry, dough-like piece of putty in your hands or on a separate piece of glass into a tube-like snake about the size of a pencil. Apply the putty to the back of the glass to cover any exposed edges and clips, working from one corner and around the perimeter of the glass.

Run the back of a plastic spoon or a putty knife down the putty to smooth it in long strokes from one corner to the other at an angle. Remove any excess putty as needed so the putty doesn’t show through the window on the outside. Leave the window undisturbed until the putty is set.