[Si Coe]

I studied chemistry at uni. In labs we made picric acid - which for those that don't know is an explosive. When its wet its totally safe, but dry its extremely unstable and slight amounts of friction can set it off. Its used in those little 'throw down' bangers kids sometimes have.

Anyway, one of our 'colleagues' (friend is the wrong term for 'annoying person that nobody likes but hangs around anyhow') was away for a few days and his flat was empty. We filled a water pistol with wet picric acid and sprayed his hall carpet through the letter box. When he returned it had dried. One foot in the door and the whole carpet went boom!

It wasn't dangerous as such - not enough to cause any damage to him or the flat (except some burn marks on the carpet) but we hadn't considered that the loud noise in a confined hallway meant he had some ringing in his ears for about a week.......