[benm (OP)]

Charles has an explosive question:

Good day, a freakish thing happened today when a glass coffee table in our office about 1 m sq x 15 mm thick exploded with a terrific loud bang. It exploded outwards we have realized as there was a delicate hour glass on the table which just dropped to the floor and is still intact. Can you possibly explain why this happened?

Anybody got a guess?

[alancalverd]

Toughened glass has a hard outer shell with the inner material under considerable pressure. Tiny scratches or surface defects act as stress multipliers and remarkably small thermal or mechanical stresses can cause the entire sheet  to shatter into surprisingly even fragments. Randomly exploding windscreens were pretty much the norm in the 1970s but most new cars use laminated glass. Toughened glass is OK in a domestic environment because the fragments aren't particularly sharp and it is clearer than laminated material. 

Interesting to have an hourglass in an office. Probably bought with matching quill pens and A4 parchment.