There are some devices, referred to as
"initiating explosives" , which transmit signals from one place to another
using electrical or chemical (non-electric) energy, in order to obtain the
of explosive charges at a controlled time.
Initiation sequences can be controlled by using electrical timing systems or chemical delay
elements. Initiating explosives systems incorporate various explosive and
inert components which may be wholly or partly consumed in the blast.
Non-electric initiation systems utilise chemical reactions, which can range
from rapid burning to violent detonation, to initiate explosive charges
either directly or via non-electric detonators. Electric initiation
systems require a device which can generate or store electrical energy
that is transmitted to electric detonators by a circuit of insulated
conductors. A combination of electric and non-electric initiating
explosives can be also used to initiate blasts.
Non-electric systems cause little disruption to surroundings as they
function and provide a high level of safety against accidental initiation
by static electricity, stray electrical currents and radio frequency
One of the key components in non-electric initiating systems is
non-electric tubing - plastic tubing coated on the inside with a reactive
powder. Non-electric tubing or signal tube is commonly attached at one end
to a non-electric detonator to form a "detonating assembly". Signal tube
has the particular advantage that it cannot be initiated by flame,
friction or impact normally encountered in mining operations.
Another commonly used initiating explosive device utilised in blasting is
the non-electric primer. A non-electric primer is formed when the
non-electric detonator of a detonator assembly is located within a
It is also known to use a cartridge of packaged explosives as a primer.
Packaged explosives consist of a paper cylinder or plastic film tube which
is filled with soft explosive composition. When used as a primer, a slit
is made in the paper or plastic and a detonator inserted.
Primer is an initiation device which consists of a container, which holds the explosive, and a cap received on the open end of the container.
The container has two lateral opposing cord tunnels which run the length of the container. The cord tunnels protect
the fuse cord on the inside of the primer. The cap has two apertures which align with cord tunnels in the container.
The cap has capwell for receiving the detonator. The capwell is pierceable so that a detonator can be inserted through
the capwell and embedded directly in the explosive composition inside the container. In addition, the primer contains grooves
in the bottom of the container and in the cap. The grooves communicate with the apertures and the recess in the cap and the cord
tunnels to create a continuous conduit so that a fuse cord can be threaded therethrough to secure the cord to the primer and selectively
position the primer in a borehole at the blast site.
A detonator 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,
or tetryl in military detonators and
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
as the primary,
and it was often mixed with potassium chlorate to yield better performance.
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.
Non-electric detonators usually take the form of an ignition-based explosive. Whilst they are mainly used in commercial
operations, non-electric 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 i.e. Conventional Munitions Disposal.
In an explosive, pyrotechnic device or military munition, a fuse (or fuze) is the part of the device that initiates function.
In common usage, the word fuse is used indiscriminately. However, when being specific (and in particular in a military context),
the term fuse describes a simple pyrotechnic detonating device, like the cord on a firecracker, whereas the term fuze is
used to indicate a more sophisticated ignition device incorporating mechanical and/or electronic components e.g. a proximity fuze
for an M107 artillery shell, magnetic/acoustic fuze on a sea mine, spring-loaded grenade fuze, pencil detonator or anti-handling device.
Modern day safety fuses are often used in mining and military operations, to provide a time-delay before ignition,
and they more often than not are used to initiate an explosive detonator, thereby starting an explosive chain reaction to detonate
a larger more stable main charge. Safety fuses are typically colored black (military) or fluorescent orange (commercial) to distinguish
them from detonating cords such as Primacord, which are brightly colored or transparent.
Fuses are found in fireworks, model cannons, matchlock firearms, some improvised explosive devices and many forms of pyrotechnics.
- A slow match is a very slow-burning fuse consisting of a hemp or cotton rope saturated with an oxidizer such as potassium nitrate.
Slow matches are used as a source of fire for manually lighting other devices, such as matchlock guns, or fuses on black powder cannons.
Before percussion caps, slow matches were most suitable for use around black powder weapons because it could be roughly handled without going out,
and only presented a small glowing tip instead of a large flame that risked igniting powder supplies nearby.
- A black match is a type of fuse consisting of cotton string coated with a dried slurry of black powder and glue. This acts as a simple pass-fire,
and was used to fire ancient cannons. They are used today in fireworks construction.
- A quick match or piped match is a type of black powder fuse that burns very quickly, some hundreds of feet per second. They consist of black matche
covered with a loose paper wrap (pipe). When lit, the flame propagates quickly down the paper pipe from the hot gases produced by the burning powder.
Quick matches are used in professional fireworks displays to pass fire nearly instantly between devices that must be physically separated while firing
simultaneously, such as a finale rack. Devices which should fire in sequence can be branched from a single master fuse, consisting of quick match spliced
onto Visco fuses of various length for time delays.
- A visco fuse has a core of black powder with one or more textile overwraps, The outer layers may be coated with wax or
nitrocellulose lacquer for water
resistance. These fuses are widely used in modern pyrotechnics because they burn at a uniform rate, with an easily visible external flame.
Depending on their outer treatment, visco fuses are water resistant and the better quality can burn reliably underwater once lit, since the
black powder core provides both its own fuel and oxidant.
- A safety fuse consists of a black powder core in a textile tube, covered with asphaltum or other waterproofing agent, and having an outer
wrapper of tough textile or plastic. They are made in a standard diameter designed to be crimped into blasting caps. Once ignited, safety
fuses will burn underwater, and have no external flame that might ignite methane or other fuels such as might be found in mines or other
industrial environments. Safety fuses are manufactured with specified burn times per 30 cm, e.g. 60 seconds, which means that a length of fuse 30 cm
long will take 60 seconds to burn. Manufacturers warn that although every effort is made to insure uniform burn times, safety fuses are subject to
variation depending on conditions and should be used with adequate safety margins.
- An Igniter Safety Fuse Electric (ISFE) lights a main fuse or device when activated by an electrical current. They typically consist of a pair
of wires leading to a thin resistance wire that heats when current is applied. The resistance wire is covered by a bit of pyrotechnic composition
that ignites from the wire heating, providing enough fire to reliably ignite the main fuse via a mechanical connection, or the device directly.
Estes model rocket motors are lit by a type of electric match. Large fireworks displays are launched with complex timing sequences using a computer
that energizes electric matches connected to the individual device fuses.
- A flying fish fuse (bumblebees) is an unusual type of component for fireworks. It is made like Visco fuse, but contains a metallic spark composition
or other effect instead of black powder. Flying fish can thus perform as a main effect instead of just an initiator. For example, simply lighting a
short piece of flying fish on the ground makes it fly through the air, seeming to swim in random directions, while emitting sparks and noise.
A aerial shell loaded with many such pieces results in a beautiful myriad of pieces flying and sparking high in the air.
- A spoolette is a delay fuse consisting of a hollow wooden dowel rammed full of black powder. A spoolette is glued into the wall of a fireworks shell
and ignited by the lift charge that launches the shell into the air. The spoolette, after a delay that allows the shell to reach its top of trajectory,
ignites the shell's main effect(s). The tough wood construction ensures that the fuse burns reliably despite the explosive force and acceleration of the
- The saucisson was an early form of fuse.