Why glass is transparent—and why it can break

Ordinary glass is an amorphous solid whose electronic structure allows much visible light to pass through while its brittle structure limits how it handles cracks.

MaterialsGlass

Editorial review: August 12, 2026 · Julian E. Marston

No long-range crystal lattice

Glass lacks the repeating atomic arrangement of a crystal.

Visible transparency depends on absorption

Many common glasses do not strongly absorb visible wavelengths over typical thicknesses.

Cracks concentrate stress

Small flaws can greatly reduce strength.

Treatments change behaviour

Tempering and laminating can alter how glass carries stress and fails.

This page explains scientific concepts for general learning. It does not replace laboratory safety procedures, professional engineering guidance, or individualized medical advice.