To replace a window glass, remove the putty, and take out the old glass and metal glazing points. Remove old paint and the rest of the putty by sanding the grooves, and apply sealer to the grooves. Coat the grooves with glazing compound, and set the new glass in place. Put new glazing points in place, making sure not to push them in. Add another layer of glazing compound, and paint the frame.
You may have to remove newer windows to replace the glass. To do this, release the channel pins by applying gentle pressure to the flexible vinyl channels. You can usually replace glass in older windows without taking them out.
Newer widows usually feature putty in the form of vinyl glazing strips that are easy to pull out. To remove traditional glazing, first soften the putty using a heat gun or torch. After the putty softens, remove it with a putty knife. Make sure not to damage the wood when removing the putty.
When applying glazing compound for the second time, make sure to apply the same amount of pressure to the tube to get an even line of glazing. Keep the tip close to the edge of the glass, and use a wet finger or cloth to make the glazing layer look smoother and shinier. If you are using latex glazing, you can paint the window frame on the same day.