A detonation explosion occurs when the material receives a sudden shock or jar. A shock wave passes through the material. All particles break down together, and the explosion is complete in a few millionths of a second. Detonating explosives are usually subdivided into two categories, primary and secondary. Primary explosives detonate by ignition from some source such as flame, spark, impact, or other means that will produce heat of sufficient magnitude.
Secondary explosives require a detonator and, in some cases, a supplementary booster.
A few explosives can be both primary and secondary depending on application. Dynamite explodes by detonation. Smokeless powder set off by a flame burns rapidly but not violently. If, however, a cap, or primer, or a fuse of some detonating substance such as mercury fulminate is set off in contact with the guncotton, the latter will be detonated. A stick of dynamite can be set on fire with a match without great danger but will explode with shattering force in response to a fulminate cap.