Scenes: Storm clouds approach Cuesta Verde and a tornado attacks the Freeling residence.
How They Were Done: A “cloud tank” was used for some of the effects shots. A 7×5 tank was built with 2 1/2in thick glass, which is half-filled with salt water with a peice of plastic rolled onto the surface, which is then covered with fresh water, filling the entire tank. The plastic is then removed, creating a soft, flat layer. Paint is then squirted into the tank and softly flows into the water. A device sometimes called “the atomic arm” is used to manipulate the paint into cloud shapes. The effect was used for several other films, such as Close Encounters of the Third Kind and Child’s Play, in the pre-CGI era.
For the shot of Robbie watching the clouds approach the suburbs, a composite shot of cloud tank footage and a matte painting of Cuesta Verde was used. The clouds were designed by Gary Platek and Garry Walker. Platek had previously generated cloud effects for Raiders of the Lost Ark, from which two of these shots were lifted for sky plates in the tornado sequence. Platek and Walker created the shots in two weeks, using blue and orange colored shots. Some touch ups, such as the base of the cloud and the shadows on the hillside, had to be made to shot via matte painting to make the shots blend better.
For the establishing view of the tornado, the tank was once again used, but this time with a sock , with air bubble, via a high speed impeller and bubble generator used to give the vortex its form. Gary Platek talked about the effect in Cinefex Magazine (#10):
“What we finally decided upon was a rotor impeller that we placed in the bottom of the tank, with a drive shaft linkage that connected to a one-horsepower motor. Interestingly, there’s a pulley you can stick into a breaker that stirs itself and is known to make a vortex. So we copied that and made our own vortex, which at full force measured about two feet high.”
But that wasn’t enough. The effect was too smooth and was clearly made up of water, so a bubble wand (a device that uses compressed air to create hundreds of tiny bubbles) was attached to “the atomic arm” to make the funnel more convincing. Each shot had to be done quickly, as the process had a would eventually fogging up the whole tank as a result.
For the shot in which we get a glimpse of the tornado’s innards as the tree is sucked into the funnel, a spinning cotton cone was formed and mirrors were used to photograph the proper angle. The miniature tree, shot against blue screen using motion control technology, was then composited into the shot.
