Old School Effects: The Cloud Tank


Following my recent rants about computer generated effects (here and here), I thought it would be fun to look into one of the old school visual effect techniques that computers have now rendered obsolete.

Today's subject is... The Cloud Tank.



A cloud tank is basically a big water tank.

It's primarily used to create a wide variety of atmospheric effects, mainly clouds, hence the name. Back in the old days this was a great way of creating organic shapes, which would otherwise have to be done with hand-drawn animation or perhaps smoke.

A cloud tank shot starts with a big glass tank. The tank used on Close Encounters of the Third Kind (1977) was 7 by 7 feet large, with a depth of 4 feet. First the tank is filled salt water. A thin layer of plastic is gently placed on top of this. Then the rest of the tank is filled with fresh water. Once the plastic is removed, and the water has been left to set for a while, you end up with something that looks like a single body of water, but because of the difference in density between salt water and fresh water there's actually two distinct layers in the tank now.

Next, paint would be gently injected into the tank, near the point where the two layers meet. Depending on the light conditions, camera speed, and a few other elements, it will look like billowing clouds when the paint disperses in the water

From what I gather, there are slight variations in the way the technique is used from project to project, but what I've described here is the basic starting point. These cloud elements would then be combined with live-action footage, or model photography, to produce a really cool, very organic looking shot.

The problem with using this technique, however, is that you're never really sure what you're going to get, and it's impossible to control precisely what happens. Basically you just have to keep shooting, and hope to catch something cool on film.

According to Douglas Trumbull on The Making of Close Encounters of the Third Kind Scott Squires was responsible for thinking up the specific setup used on that film. The same tank and a similar setup was also used on Raiders of the Lost Ark (1981), and other subsequent projects at ILM. However, Ken Ralston speculates in Cinefantastique that a similar technique was used all the way back in The Ten Commandments (1956).


Let's look at some classic examples of the cloud tank effect. We'll begin with Close Encounters of the Third Kind (1977).

Throughout the film the arrival of alien ships is often signified by the appearance of massive cloud formations. When the aliens kidnap young Barry from his mother it starts like this:

Later in the film, when the aliens arrive at Devil's Tower, a clear night sky is suddenly covered with clouds that seem to come from nowhere. Very spooky.

Additional animation and lighting effects could be added in post-production, or live during the production of the cloud elements.

The cloud tank was dusted off again for use on Raiders of the Lost Ark (1981), which also called for some angry cloud images. First there's the sequence, where Indy and his men dig through to the Well of Souls.

Hand-drawn lightning effects were added in post-production to enhance the dramatic shots.

Cloud tank elements also played a part during the last moments of the climactic sequence, where The Ark is opened and all hell breaks loose. In one shot the clouds part to make room for a giant pillar of fire.

The cloud element for this iconic image was actually created by Gary Platek, by jumping on the hose that was used to drain the water tank! This sent a burst of water back through the system, and up through the drain in the bottom of the tank, which in turn parted the "clouds" as the shock-wave moved up through the water layers.

A far less aggressive, but no less effective use of the cloud tank came with Poltergeist (1982). Here the technique is initially used simply to create the dark clouds forming on the horizon.

Later, though, when a tornado descends upon the quiet neighbourhood, the cloud tank was once again employed as an "angry weather"-tool.

A slightly more fantastic use for the tank came with the second Star Trek film. The climax of Star Trek: The Wrath of Khan (1982) called for a submarine-like showdown between two spaceships in something called a "nebula".

On this film a white latex rubber solution was injected into the tank. Lights with colored gels illuminated the tank, which produced the otherworldly results that ended up on the screen.

To give a different look to Flash Gordon (1980), and the many different worlds the film explores, a similar use of the cloud tank was employed to produce some very psychedelic images.

For most cloud tank shots the camera would be placed outside the tank, looking up at the bottom of the paint layer, but in Poltergeist II: The Other Side (1986) the camera shot from inside the tank, to create the titular dimension.

Several passes were combined, and heavily manipulated in post-production to create the complex shots.

A more recent film, Independence Day (1996), found use for the cloud tank again. This was during the dramatic arrival of the alien ships. Here the cloud elements were also heavily manipulated, this time with the help of computers, to achieve the final look.

The film was billed as a big budget tent pole film, but it actually used a fair amount of old school effects, such as in-camera shots, even though computers were an established tool.


The use of the cloud tank in visual effects seems to have ended somewhere in the late 90s, with the advances of computer generated effects, and due to the fact that it was such an unwieldy technique. In theory, you could basically set up a cloud tank shot in your own garage, but the reality is a bit different. For example, according to Gary Platek, they used 9 tons of salt during the 6 months it took to produce the cloud tank shots for Raiders!

At the end of the day it's what ends up on the screen that counts, and not how it was achieved, but I can't help but be impressed by some of these old techniques, such as the cloud tank. The amount of effort and ingenuity it took to produce these shots is mind-boggling.

So next time you see a movie from the 80s, with some cool, or strange clouds, spare a thought for the guys who spent months in a darkened room with a tank of water, a mountain of salt and some paint.

They made the heavens move, you know.



Articles used for reference include:

Raider of the Lost Ark: The Wrath of God . . . and Other Illusions, by Don Shay
- Cinefex No. 6, October 1981

Poltergeist: Stilling the Restless Animus, by Paul Mandell
- Cinefex No. 10, October 1982

Poltergeist II: To Hell and Back, by Nora Lee and Janine Pourroy
- Cinefex No. 26, May 1986

Independence Day: Fireworks, by Tim Prokop
- Cinefex No. 67, September 1996

Star Trek: The Wrath of Khan, by Kay Anderson
- Cinefantastique, Vol. 12 No. 5 & 6

Special Features from the following DVDs were used for reference:

Close Encounters of the Third Kind, 30th Anniversary Ultimate Edition
- Released by Sony

Star Trek: The Wrath of Khan, Director's Edition
- Released by Paramount


Scott Squires' site


  1. This is a pretty great list that you have compiled here. I do agree with you that VFX can be overdone and come off as being cheesy but if used properly it can really enhance a project. I loved the FX in Kick Ass or X Men 1. The Bottom line for me is to put the emphasis on a strong script and then when needed, add in some VFX to enhance the over all movie watching experience. I work for Boogie Studio, we are a boutique style studio that specializes in high end effects for the advertising industry. Please check out some of our work and my blog and comment on it at:


  2. @Dale
    You're absolutely right: Story is king, and you bring up some great movies. I also loved stuff like District 9, and of course Inception was epic cool. Sometimes, though, the small studios make more impressive stuff than the big guys. I will definitely check out your site!

  3. Great article, I love old-school vfx and it's great to see someone who appreciates them so much! Ken Ralston is probably right about that type of cloud tank (i.e. different water density layers) going back to The Ten Commandments. However, cloud tanks in general go back further. A precursor to it could be seen in The Good Earth (1937) in which long shots of a swarm of locusts were apparently achieved with tea leaves poured into a water tank. Later, we see an unambiguous cloud tank in The Beginning or The End (1947), a drama-documentary about the Manhattan Project. Head of vfx A Arnold Gillespie found that usable film of A-bomb explosions was hard to come by. Whilst puzzling over how to simulate the A-bomb mushroom cloud, he remembered scenes in old pre-war Tarzan films he'd worked on in which the eponymous jungle-man fought with rubber crocodiles underwater; the stabbed blood-sacs released clouds which formed interesting patterns under water. So Gillespie set up a water tank and after much experimentation managed to convincingly simulate the A-bomb cloud over Hiroshima. At the end of the rather humdrum sci-fi film Satellite in the Sky (1956) an A-bomb explodes in space, an effect clearly achieved with a cloud tank, and Toho's vfx supremo Eiji Tsuburaya got in on the act in 1961 in The Last War; the H-bomb explosion over Tokyo appears to use a combination of techniques, including a cloud tank and animation.

  4. @McToddd wait wait wait... Stop mentioning titles I have to get! No, seriously thanx for the info. I'm gonna try to check these out. Old school efffects are pure magic!

  5. Ha ha, the Curse of the Internet, it makes you go out and buy stuff! If you get the double-DVD set of Rodan and War of the Gargantuas, there's a smashing documentary extra called Bringing Godzilla Down To Size in which a bunch of old-time, and current, Japanese vfx guys get together and show how they did an erupting oceanic volcano from Latitude Zero (1969) using a big water tank and pots of different coloured paints (red, brown and two shades of grey) tipped into the water which they shoot on video with the tank in front of a greenscreen; they then flip the picture vertically so the paint, which is dropping down into the water, looks like smoke shooting up into the sky; the boundary between the water and air looks just like the surface of the ocean even though shot from underneath!

  6. Sounds fantastic! I'm gonna get my hands on that! Thanx McTodd!

  7. Disney's used the tank idea in the Rite of Spring segment of Fantasia for the lava sequence in the beginning and as a wipe from one period of time to another under the water when life is forming. They didn't use salt but poured the paint into the tank through black tubes and filmed them upside down to create the plumes of smoke rising up.

  8. Fascinating and informative post. The eerie clouds throughout Poltergeist, especially in the first third of the film, really worked very well in constructing an atmosphere of, if not the supernatural, at least the preternatural. You can feel it watching those clouds that are not *quite* right. There's something unwholesome in the skies above Cuesta Verde, hinting at the horrors beneath it. The technique seemed to provide that chaotic or unnatural look that made them so memorable.

    I love the clouds in Poltergeist II as well, especially that ghostly white one that billows out from a black sky above the house.

    Correct me if I am wrong, but this technique was used in The NeverEnding Story, too, yes? It worked so well for depicting the Nothing, if in fact that's what they used.

    Great post. Great blog! Thank you.

    1. This is exactly why I googled "How'd they make cloud effects on older movies."

      The cloud effects in Neverending Story were amazing and I always wondered how it was done since it was before the ample use of CGI.

  9. On "Ghostbusters" and "2010" we worked some loooong days, and far into the night. I remember crawling under the cloud tank sometimes, stretching out on salt bags, catching a short snooze.

    1. Hahah, sounds like a nice, quiet moment in the middle of what must have have been a horrible mess. Can't imagine working with these tanks and all that salt. Still, the results are unmatched, even by today's standards.

  10. Love the effects and production design from the earlier years. Those cloud tank effects are authentic and eerily brilliant! We're testing the waters on doing it at Imagination Workshop Studio but would love some help from the pro's that did them in my favorite pictures.