When the putty on your windows starts to dry out and crack, it will cease to function properly. The glazing putty on the window creates an airtight seal that keeps wind from blowing in and heat from escaping. When this putty starts to deteriorate, the water and cold air can leak through, and the occasional pest can gain entry. A do-it-yourself homeowner can easily replace this putty on their windows with a few simple tools.
Step 1 - Remove Old Putty on Windows
Before putting more putty on windows you will need to remove the old putty that is already there. Use a putty knife to break the existing putty up into smaller pieces. Scrape away until you have removed what you can without going too hard. This will probably be the larger pieces.
Step 2 - Heat Putty with Heat Gun
Trying to remove all of the putty with the putty knife will only result in gashes in the wood frame and scratches on the window pane. Once you have removed all that you can with the putty knife, use a heat gun to soften up the remaining putty. Hold the heat gun about eight to 10 inches away from the wood and continually move it back and forth across the section with putty. Don't hold it too close—too much heat will crack the window. Work at the soft putty with a plastic scraper or small putty knife. Make sure it's all removed.
Step 3 - Remove Window Pane
Carefully remove the glass from the window pane. Once most of the putty is removed, the glass should come out easily. Press from the opposite side of the window. If you don't think you can carry the window yourself without breaking it, get someone to help you with this step.
Step 4 - Remove Remaining Putty
Once the window glass is out you will then be able to remove the remaining putty from the frame and the glass. Wipe the glass down once the putty has been removed.
Step 5 - Apply Linseed Oil
After the frame is clean of all putty, rub some linseed oil over the area where the new putty will be applied. The linseed oil will help keep the wood from drying the putty out too quickly. Use a clean rag and wipe off the excess oil from the frame.
Step 6 - Apply Putty to Windows
Take an amount of putty in your hands and knead it into a small rope. Place the putty in the groove where the window pane will be placed. If the glazing points came out and there is no groove, then replace the points before you put the glass in.
Step 7 - Reinstall Window Pane
Press the window back into position and hold it firmly onto the putty.
Step 8 - Smooth out Putty
After the window has been pressed into the putty, recheck to make sure that there is an even distribution of the putty around the window. If not, then apply more putty in those areas. Place a small rounded ball of putty at the location and press down with the glazing tool. Once the putty is universal around the window, smooth it out with the glazing tool. Hold the tool at a 45-degree angle and gently smooth out the putty. There should not be any more than ¼-inch of putty on the window pane itself.
Step 9 - Paint Putty
After the putty dries, apply some paint so that it is the same color as the frame or window treatment. Depending on which kind of putty you used, this may mean coming back to paint it several weeks later (glazing putty has been known to take 30 days to dry to the point where you can paint it).