If your window glass accidentally broke into pieces, replacing it would be a good remedy for it. But it is easier to detach smaller pieces from the window frame than one unbroken piece. You will possibly find that, even after you remove the putty and the points, the window still won’t come out.
Usually, heating the glass with the heat gun around the perimeter will sufficiently soften the old putty to allow you to remove the old glass. If this also fails, then you may have to break the glass to remove it. If the glass does not come out with a light tap or two, it may be glued in place by the old putty that was used to “bed” the glass. This bedding gives a better air seal and allows the glass to seat tightly against the frame when you set the points.
To keep glass fragments from flying everywhere, use duct tape and cover the inside of the glass. If it’s a large pane, duct tape a heavy plastic trash bag before you start breaking it out. Once done, you can use a hammer and nail set to sharply crack the glass into a malleable mass.
Some window frames have a slot in the top of certain panes that the glass slides into. You will generally find this on the upper panes of the lower sash of a double hung window. If this is the case for the pane you are replacing, measure the height of the frame and add 1/8″. There is no need for the glass to slide all the way into the slot.
To bed the glass apply a thin bead of putty to the frame. Then press the glass into it. The idea is to seal the glass against the front of the frame. You should see the putty squeeze between the glass and the frame. If a little squeeze out of the back, that’s fine, you can clean it up later.
Once the glass is tight against the frame, insert the points. Do the same layout as the original. To insert the points, put one against the glass with the point down into the wood. Use your putty knife to wiggle-push the point down until it is seated at a height below the final height of the putty. It takes a knack that you’ll get really fast! If you bought points, you may have gotten an insertion tool packaged with them. Use it if it seems like it will help you. If you use this tool, you can use a hammer instead of the putty knife, but be careful doing any whacking near the glass.
Window replacement is considered necessary when it becomes broken or damaged. Homeowners may worry about the expense or problems associated with replacing the glass, but this actually easy because of the large number of retailers selling types of replacement glass and you can choose from a wide variety of glass type so cost could be reduced.
