If you are out purchasing window pane replacements, the glass has to be a little distant from the dimensions of sash. In case the sash proves to be truly straight and square, the clearance allowed between the dimension of glass and that of the sash has to be equal to or more than 1/8th of an inch. If you find the sash a bit questionable, be sure to maintain nearly half of the ledge width, against which the glass gets to rest.
If it is doable for you, go ahead and get the sash of window removed from the frame, but in case doing this seems too complex, it is perfectly possible to do the entire work into one place. All the old glazing points and compounds need to be chipped out and pulled out respectively after the cracked glass is detached from your window. Have the frame of the window cleaned thoroughly, and use oil-based paint to paint the same, so as to make sure that old compounds and paints do not continue to exist in the frame groove.
You have to get little amount of glazing compounds warmed, by simply rolling between the palms of your hands. Work the same into rope of small size, and the ledge in which the glass rests, press it. This particular step is known as “bedding”, and demands quite low amount of glazing compounds. Note that the “bed” in which the glass is rested has to be pretty thin.
With utter care, push or gently press the glass pane, making sure that there is total contact between the glass and the bedding. Press glazier’s points inside the sash using a putty knife, pressing in as well as down simultaneously. Forcing the glass thoroughly into the bedding is a good idea; however, applying heavy amount of force may have the pane cracked in no time. If a window is large, put glazier’s points after every 4 inches, however, for medium or small windows, 2 glazier’s points on each of the sides can be enough.
Turning over the sash, remove or clean the glazing compounds that exist in the sash or glass. The next part consists of utilizing the sash edge as some kind of visual guide with a view to shaping the glazing compound. Cutting straight lines becomes truly simple when sash edge can be seen with clarity.
Have some more of the compound warmed, and work the same into the corner shaped by the glass and the frame of the sash. Position the putty knife in such a way that its point seems to line up with the frame of the sash located opposite to the glass. The blade should rest against the frame of the sash. You may find there is a triangle shaped by the sash, the glass and the knife, and when you pull your knife, the compound that is outside this particular triangle will get cut nicely.
You should observe a clear line emerged between the excess compound, and the window seal shaped newly. The finished seal should have the excess away, for which you need to use the knife.
Have the steps repeated for other window panes, and for a few weeks, let the glazing compound rest. After this period, you may go ahead and apply your final paint.