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Have you looked at the glazing putty around your windows lately? If so, chances are you noticed some cracked, broken or entirely missing strips of putty. The fact is, all single-pane windows need reglazing periodically. Replacing cracked putty will save energy and prevent rot from invading your windows. 

Start your glazing project by removing any screen, storm or combination window that might be in place. Then look to the most deteriorated strip of putty and start chipping it away with a rigid, chisel-edge putty knife. Old, rock-hard putty may first require heat to soften it. Use an electric heat gun, rather than a torch to reduce the risk of fire. 

Once the putty is out, remove the half-dozen glazer’s points that lock the pane against the sash frame. These will either be diamond-shaped metal points or formed metal clips. Use a needle-nose pliers or screwdriver to unseat them. 

To remove the glass, go indoors and press evenly against the bottom of the glass pane. When the glass is pushed just past the bottom rail of the sash, go back outside, grasp the pane (with heavy gloves) and pull down steadily.  

Because glass is usually seated firmly in a slot in the top rail of the sash, you may need to twist and tweak it a bit, until it breaks free. If the pane is broken, remove the loose pieces first. 

When the glass pulls free, brush the L-shaped recess with a wire brush and wipe away loose particles. Then use a utility knife to pry the remaining putty from the top slot of the sash. 

To install new glass, slide the pane from below into its upper slot and gently press the bottom against the sash.  

If the pane won’t slide into its recess at the bottom, slip a putty knife into the recess and gently pry the glass until it clears the recess edge. Then secure the pane with glazier’s points. Press the points into the frame with a screwdriver or a putty knife. 

Install a bead of putty all around the window. Soften the putty, if necessary, before  

using it by rolling a glob of it in your hands.  

Smooth the putty by drawing a clean knife along the joint. Carefully trim away any excess when finished. 

In most cases, you’ll want to paint the glazing when it’s had a few hours to skin over. Don’t worry about getting paint on the glass. Overpainting makes painting easier and also helps seal the joint and picks up the oily film left on the glass by the putty. The paint dries in a few hours, so just scrape the glass clean with a single edge razor blade.