Video Explosives & Blasting Caps: "Demolition: Electric Priming" 1957 US Army Training Film

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Demolition: Part II: Electric Priming "Most of the demolition work accomplished in today's Army is done by means of insensitive-type explosives. In order to detonate them, you need a small explosive charge powerful enough to set off the main charge. This smaller charge is the blasting cap..."

US Army Training Film TF5-3787

Public domain film from the US National Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).

http://creativecommons.org/licenses/by-sa/3.0/
https://en.wikipedia.org/wiki/Detonator

A detonator, frequently a blasting cap, is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the latter two being the most common.

The commercial use of explosives uses electrical detonators or the capped fuse which is a length of safety fuse to which an ordinary detonator has been crimped. Many detonators' primary explosive is a material called ASA compound. This compound is formed from lead azide, lead styphnate and aluminium and is pressed into place above the base charge, usually TNT or tetryl in military detonators and PETN in commercial detonators.

Other materials such as DDNP (diazo dinitro phenol) are also used as the primary charge to reduce the amount of lead emitted into the atmosphere by mining and quarrying operations. Old detonators used mercury fulminate as the primary, often mixed with potassium chlorate to yield better performance.

A blasting cap is a small sensitive primary explosive device generally used to detonate a larger, more powerful and less sensitive secondary explosive such as TNT, dynamite, or plastic explosive.

Blasting caps come in a variety of types, including non-electric caps, electric caps, and fuse caps. They are used in commercial mining, excavation, and demolition. Electric types are set off by a short burst of current conducted from a blasting machine by a long wire to the cap to ensure safety. Traditional fuse caps have a fuse which is ignited by a flame source, such as a match or a lighter...

Need for detonators

The need for detonators such as blasting caps came from the development of safer explosives. Different explosives require different amounts of energy (their activation energy) to detonate. Most commercial explosives are formulated with a high activation energy, to make them stable and safe to handle so they will not explode if accidentally dropped, mishandled, or exposed to fire. These are called secondary explosives. However they are correspondingly difficult to detonate intentionally, and require a small initiating explosion. This is provided by a detonator.

A detonator contains an easy-to-ignite primary explosive that provides the initial activation energy to start the detonation in the main charge. Explosives commonly used in detonators include mercury fulminate, lead azide, lead styphnate and tetryl and DDNP. Blasting caps and some detonators are stored separately and not inserted into the main explosive charge until just before use, keeping the main charge safe.

Detonators are hazardous for untrained personnel to handle since they contain primary explosive. They are sometimes not recognized as explosives due to their appearance, leading to injuries.

Types

Ordinary detonators

Ordinary detonators usually take the form of ignition-based explosives. Whilst they are mainly used in commercial operations, ordinary detonators are still used in military operations. This form of detonator is most commonly initiated using safety fuse, and used in non time-critical detonations e.g. conventional munitions disposal. Well known detonators are lead azide, Pb(N3)2, silver azide (AgN3) and mercury fulminate [Hg(ONC)2].

Electrical detonators

There are three categories of electrical detonators: instantaneous electrical detonators (IED), short period delay detonators (SPD) and long period delay detonators (LPD). SPDs are measured in milliseconds and LPDs are measured in seconds. In situations where nanosecond accuracy is required, specifically in the implosion charges in nuclear weapons, exploding-bridgewire detonators are employed. The initial shock wave is created by vaporizing a length of a thin wire by an electric discharge. A new development is a slapper detonator, which uses thin plates accelerated by an electrically exploded wire or foil to deliver the initial shock. It is in use in some modern weapon systems. A variant of this concept is used in mining operations, when the foil is exploded by a laser pulse delivered to the foil by optical fiber...