How can a tiny shard of ceramic from a spark plug shatter car glass?

Tempered automotive glass used for side windows has internal stresses created during the manufacturing process.

These stresses make the glass extremely strong in bending and tensile strength, but also sensitive to pitting.

When a sharp ceramic shard hits the glass, it concentrates the full force of the impact into a tiny area, overcoming the internal stresses and causing instant destruction.

Ceramics are highly hard, and when struck in a small area, a tremendous force is generated that shatters the glass at that exact point.

This process is known as the “point impact effect” and it allows a small shard to shatter a massive surface that would normally withstand significant stresses.

This phenomenon has been described in both technical sources and criminological studies.