- 1). Remove the old glass carefully, wearing gloves and safety goggles. If the pane isn't broken, carefully chip out old glazing (putty used to seal each pane of glass to the frame) and glazing points (small metal anchors used to hold the glass in place until it's glazed) with a small chisel until you can remove the glass. Soften the glazing with a heat gun or even a blow dryer on a high heat setting to help ease this process.
- 2). Measure the opening, then subtract 1/8 to 3/16 inch from the vertical and horizontal measurements. You don't want the glass to be jammed tightly in the opening.
- 3). Purchase new glass with the appropriate dimensions. Any glass shop and many hardware stores and lumberyards can cut the glass to the size you need.
- 4). Set your new glass in place, and use at least two glazing points on each side (more if the opening is larger than 12 inches square). Don't press too hard against the glass, or you may break it.
- 5). Work the glazing against the glass and the window frame. Smooth it down with a putty knife or a glazing knife, which looks like a putty knife with a bent end.
- 6). Let the window set for 24 hours before opening it.
- 7). Paint the glazing to protect it, following the directions the glazing came with. Some manufacturers suggest waiting for several days or even longer before painting.
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