Going out with a bang

One of the great chemical inventions is the detonator – a small explosive device which sets off a big one. The idea seems to have been started about 1800, when the Scottish clergyman Alexander Forsyth devised his ‘percussion cap’ for hand guns. Previously, most hand guns had been ‘flintlocks’: when you pulled the trigger, a piece of steel struck a flint and the resultant spark set off a pan of gunpowder. From here, a tube carrying the powder conveyed the flame to the firing charge. Quite often this system went wrong; if the ignition failed to follow the gunpowder down the tube you merely got ‘a flash in the pan’.