In the first, burning begins at one end of the charge and travels with blinding speed through the entire charge. Complete combustion of a reasonably large charge takes only a few thousandths of a second. Gunpowder explodes in this way. 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.