The final step is both functional and aesthetic: creating the sloped putty seal that sheds water and secures the pane. Roll a portion of fresh glazing putty between your palms into a rope about the thickness of a pencil. Press this rope firmly into the corner where the glass meets the frame, running it continuously around the entire perimeter. Now, take a clean putty knife and, holding it at a consistent 45-degree angle, smooth the putty into a neat, sloping bevel. The tool should ride along the glass and the frame simultaneously. Wipe away any excess putty from the glass surface with a rag slightly dampened with mineral spirits. Allow the putty to cure for at least 7 to 14 days before painting—this curing time is non-negotiable for a durable finish. During this period, protect the window from rain and extreme temperatures.
Before touching a single shard of glass, safety must be the absolute priority. Put on a pair of heavy-duty work gloves and safety glasses to protect your hands and eyes from sharp edges. Begin by carefully removing any loose glass from the frame, placing the pieces directly into a cardboard box or a doubled-up paper bag for disposal. Use a stiff putty knife and a pair of needle-nose pliers to extract any remaining glass shards still gripped by the glazing putty. Once the large pieces are gone, lay a drop cloth or old newspaper on the floor below the window to catch any falling debris. Take a moment to measure the opening precisely: measure the height and width of the rabbet (the inner ledge of the frame) in three places each, using the smallest measurement to ensure a proper fit. Then, subtract 1/8 inch from both dimensions to allow a slight expansion gap for the new glass. Have this glass cut to size at a local hardware store. how to replace a broken window pane