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Physical effects include wind, fog, smoke, rain, snow, fires, explosions, and gunshots. They require hand of a highly trained professional, especially when their use can endanger the safety of the cast and crew. Wind is usually generated by very large fans or aircraft engines and propellers whose speed and direction can be carefully controlled. Fog is often produced by combining smoke, such as from slow burning naphtha or bitumen mixtures, and dry ice, which produces carbon dioxide. Most smoke – producing devices use either oil or water – based smoke fluid, which is heated above the boiling point to produce a gas that looks like smoke. Because all smoke is toxic to some degree, it should only be used in well – ventilated areas.
Rain, like wind and fog, is often used to accentuate a mood and atmosphere. Ground level rain stands and overhead rain heads can be used to produce rain in limited areas, and the surrounding areas can be wetted down before shooting to sustain an illusion of a general rain shower. When rain effects are produced in a sound stage, it is extremely important to waterproof the floor, to have a means of drainage or water collection, and to avoid any contact between water and electrical equipment, such as light, which could cause severe injury or even kill cast and crew members.
Snow can be created indoors or outdoors using a large, almost silent, wooden – bladed fan, which can also be used for rain effects, that is called a Ritter fan. Plastic snow can be dropped in front of the fan, usually from the top of the left side but never from behind (which foul the blades and mechanism), by hand or a snow delivery machine. Polystyrene granules can be added to create a blizzard effect. Outdoors, a variety of materials, in addition to plastic flakes, can and have been used to create snow, including shaved ice, foam machines, gypsum, salt (on windows and window sills), and aerosol shaving cream on slippery surfaces.
Although fire effects can add excitement and visual interest to a scene, they are also extremely dangerous and should only be created by skilled professionals who know how to contain them. It is extremely important to have fire extinguishers on hand that can control all three classes of fire: Class A fires, which burn solid combustibles such as cloth, rubber, wood, paper, and many plastics; Class B fires, which burn flammable liquids and gases; and Class C fires, which involve electrical or electronic equipment.
Explosions and pyrotechnics are the most difficult special effects to perform safely. They need to be set up and supervised by experts who are thoroughly familiar with the setting, detonation, and control of explosions and fires, because they are potentially dangerous to cast and crew members. The U.S. Bureau of Alcohol, Tobacco, and Firearms control explosives and pyrotechnics. A federal license is needed to use explosives, and information concerning their use can be obtained from the bureau upon request. Most explosions and pyrotechnics require remote detonation.
Bullet hits are created by remote detonation of small explosive devices, called squibs, which are positioned over body armor or a hit plate that protects the actor or stuntman. Blood packs, consisting of plastic bags containing corn syrup and red food coloring to simulate blood, and squibs are glued onto the back of the actor’s or stuntman’s shirt. Wires running down the pant legs are attached to the squibs at one end and to the firing box for remote detonation at the other end. Sometimes the wires have breakaway connectors at the ankles so that the actor or stuntman can break free of the wires just after bullet hits have been detonated.
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