These substances are utilized in explosives preparation and necessary to provide a sudden burst of flame to ignite an initial detonating agent, a propellant, a fuse powder or a pyrotechnic material. They are used in blasting caps, fuses, primers for small arms and artillery weapons, rocket igniters, incendiary devices, fireworks and signaling devices such as flares.
Priming compositions are ignited by friction, impact or flame. Many of these consist of mixtures of one or more initial detonating agents with oxidizing agents, fuels, sensitizers, and binding agents. Some contain additives which serve more than one purpose. An example of such an ingredient is gum arabic which can work as both a fuel and binding agent. Additives may dilute the initial detonating agent so much that its decomposition becomes a rapid combustion rather than a detonation. Earlier priming compositions used mercury fulminate as its main explosive agent and have since been largely replaced by compositions based on lead azide and other substances.