sapphire isn't the second strongest material. most steels and fiberglass are stronger. it is the second HARDEST known material, but that's a different property. ultimate tensile strength of steel is higher because it is more resistant to plastic deformation. sapphire, on the other hand, is not and enters plastic deformation with much less deflection, hence the term brittle. 🙂 (see mom, i did learn something from engineering school!) regardless, the flexibility of the glass in the video is what is amazing. any glass with an elastic zone that large is probably really scratch resistant.