The putty between your wood windows and the glass is called glazing. It keeps your windows in place and provides an airtight seal. When your glazing becomes old and weathered, it can begin to crack and fall out. It is important to replace missing glazing to stop warm or cold air from escaping or entering your home through your windows. In addition, replacing your glazing will lower the cost of your utility bills.
Remove all loose and cracked putty or glazing from around your windows. Slide the tip of your screwdriver into a crack in the putty and pry up. Loose putty will easily come out.
Remove the rest of the putty. Place the tip of your screwdriver at the exposed edge of the putty. Lightly strike the handle of your screwdriver to break the putty loose from your window frame. Make sure that the tip of you screwdriver is facing to your left or to your right. You do not want the tip of your screwdriver pointing toward your glass. Continue this step until you have removed all of your putty on your wood windows.
Brush out all loose particles around your window frame and glass with a paintbrush. Clearing away loose particles will improve adhesion of your new putty.
Scoop out a quarter-size amount of putty or glazing with your putty knife. Place the tip of your putty knife against your glass at the point where your glass and window frame come together, beginning at the lower left corner of your window. Press the putty into your window frame and pull your putty knife down at a 45-degree angle, away from your window. Continue working your way around your window until you have filled your frame with putty.
Moisten your rag with paint thinner and wipe your putty knife clean. Hold your putty knife with the blade facing to your left. Tilt your putty knife at a 45-degree angle. The high point should be closest to your glass. Lightly drag your putty knife across the putty to smooth it out.
Use the tip of your putty knife to carefully remove excess putty on your glass. A small line of putty will get on your glass while you are smoothing the putty across your frame.
Wait two to four weeks before you paint your putty. It will take at least this long before it is fully cured.