3. The role of glass surface and structure

3.1 Glass surface and mechanical properties

Contrary to popular belief, glass is, in theory at least, mechanically very strong. What's more, its surface appears very hard, only scratchable by harder materials such as diamond. However, this surface is glass's Achilles heel. The breaking strength of an ideal glass would be of the order of 10 ¹⁰ N/m ² , a value obtained by theoretical calculation. In practice, however, observed values are 100 to 1,000 times lower, and glass is considered brittle and fragile. Why is this? It's because tiny cracks, known as Griffith faults, appear on the surface of the glass itself, named after the man who first postulated their existence in 1920. These cracks can...