The deterioration of stained glass panels is normally down to four main aspects – age, weather, inappropriate protection and vandalism. It is advisable to periodically check stained and leaded glass windows for deterioration or damage. The signs that you should look for are:

• Bulging or buckling of lead
• Damaged areas of lead and glass or cracks in glass
• panels that have become detached from the strengthening bars
• Leakages
• Areas of condensation between protective glazing and stained
  or leaded glass windows
• Loss of glass paint

 

You should retain any found sections of glass that have become detached from the window. These broken segments, however small, are invaluable during the conservation of the stained or leaded glass window.