When explosives are initiated their energy is liberated by one of two processes, burning or detonation. Most explosives are capable of either process, depending on the mode of initiation and the conditions under which it occurs. In practice these factors are so regulated as to ensure that the explosive behaves in the desired manner.

Virtually all explosives burn vigorously when ignited in a dry unconfined state. Burning can also occur in a confined state, since explosives do not rely on an external supply of oxygen for their combustion. Burning comprises a series of chemical reactions which take place at or just above the surface of the explosive. When the solid material is being converted into gases its surface, provided it is non-porous, can be regarded as receding layer by layer. The temp of each layer is brought in turn to the ignition point, and the heat necessary to do this is radiated and conducted from the reaction zone(s) into the solid material. Some heat is also evolved by the slow decomposition of the explosive before it reaches ignition point.