If your windows are leaking when it rains or letting in drafts, it may be time to put in new putty. Putty, also known as glazing compound, seals the joint between the glass pane and the wood frame of the window. To put putty into the frame, you will need to clean out the old putty, take out the glass, add new putty and replace the glass. You will need to wear safety glasses and gloves throughout the process.
Use a heat gun to soften the existing putty. Set the heat to a moderate temperature on the heat gun and apply the heat to the putty, scraping the putty away from the window with a 2.5 cm (1 inch) putty knife as it softens. Increase heat slightly if the putty isn't getting soft enough to scrape away from the window.
Use a lifting motion with the putty knife to pull the putty away from the window as you make your way around the frame. As you encounter the glazing points, small metal triangles that hold the glass in place, remove these and keep in a safe place. Glazing points are pushed into the wood; you can lift them out with the tip of the putty knife.
Carefully lift the glass from the frame. Wrap the glass in bubble wrap or other protective covering and set aside.
Prepare the putty for installation. Putty is stiff when first taken out of the package and should be kneaded to make it more malleable. Use a little linseed oil and gently rub it into the putty as you knead it. Do not add too much oil, as this will make the putty tacky.
Roll a small portion of putty between your palms, forming a pencil thin length. Apply this rolled putty to the frame, gently but firmly pushing it into the frame. Use your fingers or the flat end of the putty knife to smooth the putty.
Reinstall the glass pane. Once the frame has been puttied, gently fit the glass into position within the frame. Reinstall the glazing points, making sure the window is held steady while you push the points back in. If necessary, use a small tap hammer to drive the points into the frame.
Apply a thin layer of putty around the window where it meets the frame, pushing it into the frame as you go. Smooth out the exposed putty and remove excess with a scraper or putty knife.
Apply tape to the window in a large X to provide stability when you remove it.