One way to tell your stained glass is damaged is by looking out for signs of corrosion. If the metal surrounding the glass appears rust or deteriorated, then most likely, your window panels will also appear brownish or crusty. You can also observe whether your window or door has bulging and flaking panels, broken wires, or loose putty. Dull or loose fixtures can lead to cracks and breakages, so call for a Tasker immediately.