How to Repair Broken Glass in the Lower Sash of a Single Hung Window

Prepping the Window

1). Break the remaining glass from the pane. Use pliers to pull stubborn pieces from the old glaze. Save a piece of the glass, with edges taped and wrapped in several layers of paper, for comparison when buying new glass.
2). Scrape the old glazer's putty from all four sides of the interior frame. Use a sharp chisel or paint scraper for this process. Apply heat to soften the old putty. Use a heat gun available in most paint departments at hardware stores. Remove all of the old putty. Sand any roughness by hand.
3). Save the small metal triangles that you find under the putty, which are called points and help to hold the new pane in place until the glazer's compound hardens. You will need at least two for each side of the interior pane for a total of eight. Purchase additional points at the hardware store if needed.
4). Measure the empty opening of your window sash. Measure wood to wood, top to bottom and side to side measurements. Write these on the outside of the paper wrapping around your glass sample, and take them with you to the hardware store.
5). Order a pane of glass based on your opening measurements and the thickness of the glass from the broken pane. Most hardware stores have multiple employees trained to cut glass, and you can wait while it's cut. Typically a 1/8 inch allowance is made for fit, but they will know, based on your measurements, what size to cut your new glass. You can also get what you need from a glass company that sells retail.

1). Set the new pane into the window, and tap the points into place. Start at the top of the window to prevent the pane falling out. Use a chisel or flatblade screwdriver pressed against the top of the points and a hammer to gently tap them into position. Add two on each side of the frame.
2). Seal the new pane in place with latex glazer's compound, which is a special type of caulk designed for this application. Cut your caulking tube to an opening about as thick as a pencil. Run a bead around the edge of the glass to fill any gap between the glass and the frame.
3). Widen the tip cut slightly, and run a thick bead over the edge of the glass and back to the frame, creating a beveled seal all the way around the pane. Smooth the glaze with a dampened finger.
4). Run a bead of glaze around the outside of the pane, and work it smooth with the tip of a dampened finger. Allow the glaze to dry before painting to match.