Sparks and Flashes
Requirements for flashes range from a bolt of lightning in the sky to a flash that illuminates the scene below. Sparks occur in electrical malfunctions, safe-cutting and across huge terminals in Frankensteinian laboratories.
Because sparks suggest danger they can occasionally be used to imply something menacing. For example, a close-up of an egg in a nest would imply nothing more than an everyday object – benign and wholesome. But if that same egg were to have tiny blue sparks erupting from its shell we would presume it to be evil.
The spark coil
High-voltage spark coils manufactured for laboratory use can be employed for TV and movie effects. These coils produce bright blue sparks across their terminals (as much as 6in (152mm) apart) which, when superimposed over the main picture, can look highly dramatic.
Discharged between different shaped electrodes the sparks can be made to produce different patterns. One example is a circular cathode with a central anode. This produces a random pattern of sparks radiating like the spokes of a wheel.
Practical sparks such as these must be recorded in front of a black background. If a number of them are pre-recorded and superimposed over each other, complex interacting patterns can be built up.
Computer-enhanced sparks can be fattened and their colours altered. Computer graphics will also produce those crackling arcs that travel slowly up sci-fielectrical installations.
The scissors
The scissors, a device used by studio electricians, comprises two wooden handles hinged in the middle. At their ends they have carbon rods which, when brought together, induce an intensely bright arc. Scissors are used to simulate lightning flashes and night-time battlefield effects.
On a smaller scale an electric arc welder will produce a repertoire of sparks and flashes. A hacksaw blade connected to one lead drawn across a metal strip connected to the other will produce a shower of bright sparks.
Video camera damage
It is easy to assume that very bright light could damage a video camera, but this is not necessarily so. Most video cameras have at some time been inadvertently pointed at the sun without ill effect and there is little evidence that filming a welder at work has caused damage. If in doubt, check with the manufacturer.
SPARKS AND FLASHES
A welding transformer can be coupled up to various props which need to spark intermittently.
1. A screwdriver connected to one terminal of the welder can be thrust into switchgear connected to the other terminal.
2. An electic motor can be wired to a welder so that sparks come from the casing when the motor is rotated.
3. An electrified fence can be seen to be alive when the wires are moved.