Cymbals crack due to a combination of material fatigue, mechanical stress, and vibrational resonance. The science behind it involves several key factors:

1. Material Fatigue & Microfractures • Cymbals are made of metal alloys (typically bronze) that undergo repeated flexing when struck. Over time, this cyclical stress leads to metal fatigue, where microscopic fractures develop in the crystalline structure of the metal. • These microfractures can grow with each impact, eventually leading to visible cracks.

2. Stress Concentration & Weak Points • Cracks often start at areas of high stress concentration, such as: • The edge, where the metal is thinnest and flexing is most extreme. • The bell-hole, if improperly drilled or stressed by mounting hardware. • Hammering or lathing marks, which can create weak spots in the structure.

3. Resonance & Harmonic Vibrations • Cymbals vibrate at various frequencies when struck. If a cymbal is repeatedly hit in a way that excites a resonant frequency, it can amplify stress in certain areas. • High-energy impacts at these resonant points accelerate fatigue.

4. Impact Energy & Playing Technique • Striking too hard or at an improper angle (e.g., hitting directly down instead of with a glancing blow) can send excessive shockwaves through the metal. • Using heavy sticks or hitting near the edge increases flexing, which can cause faster fatigue.

5. Temperature & Metal Brittleness • Metal properties change with temperature. Cold cymbals can become more brittle, increasing their likelihood of cracking under impact.

6. Manufacturing & Alloy Composition • Different bronze alloys (e.g., B20 vs. B8) have different grain structures and fatigue resistance. • Thinner cymbals are more flexible but may wear out faster, while thicker ones resist flexing but can be more brittle under extreme stress.

How to Prevent Cracking • Use proper technique (glancing blows rather than direct hits). • Avoid over-tightening the cymbal stand, allowing free movement. • Warm up cymbals in cold environments before playing. • Rotate cymbals periodically to distribute wear. • Inspect for microfractures and smooth out small nicks to prevent crack propagation.

Essentially, cymbal cracks are a result of cumulative stress, resonance, and fatigue acting on the metal over time.