There are many and various causes for damage to bells. Excessive stress leaves its mark on bells.
Clappers: Many historic bells have worn out striking points on the inside of the bell enforced by the clapper, worn out or even missing parts and / or stress cracks. Incorrectly dimensioned clappers place disproportionate stress on the bell bronze and cause premature damage. The effects of different clapper dimensions have been scientifically researched by the European bell project ECC-ProBell®.
Casting defects: During the restoration of some historic bells, it becomes apparent that casting defects such as clay inclusions, porosity and missing bronze material have contributed to the damage.
Suspension iron: In the past, forged suspension irons were cast into the bells to secure the clapper. Severe corrosion can increase the volume of the suspension irons and cause cracks and breakage of bronze parts in the area of the bell crown. Increased wear and tear can lead to weakening of the suspension irons and ultimately to breakage.
Bell crowns: Broken handles and handles with grooves are the result of decades of wear and tear with extensive stress.
Throughout history, war and fire have always been the greatest enemies of bells. Fortunately, some bells have "survived". Inscription on a historic bell "Whoever touches me, the war ist lost to him, already tried twice."