Old School Effects: The Cloud Tank
Hacker News
February 19, 2026
AI-Generated Deep Dive Summary
The article delves into the fascinating history of the cloud tank, an old-school visual effects technique that has since been overshadowed by computer-generated imagery (CGI). This method, which involves creating organic-looking clouds using saltwater, freshwater, and paint, was a groundbreaking innovation in its time. Though now considered obsolete due to advancements in CGI, the cloud tank played a pivotal role in shaping iconic moments in films like *Close Encounters of the Third Kind* and *Raiders of the Lost Ark*. The technique’s charm lies in its ability to generate unpredictable yet stunningly realistic cloud formations, offering a unique visual texture that was hard to replicate with other methods.
The process begins by filling a large glass tank with saltwater, then layering it with freshwater. A thin plastic sheet is placed on top of the saltwater before adding freshwater to create two distinct layers. Paint is injected at the water’s interface, dispersing and creating cloud-like shapes that respond to lighting and camera speed. This organic approach allowed filmmakers to capture dynamic, atmospheric effects, often combined with live-action footage or model photography for seamless results.
Despite its limitations—such as the inability to precisely control outcomes—the cloud tank delivered unforgettable visual moments. For example, in *Close Encounters*, it created swirling clouds signaling alien arrivals, while in *Raiders of the Lost Ark*, it enhanced dramatic sequences like the parting of clouds for a fiery pillar. Even *Poltergeist* utilized the technique to create eerie, stormy skies, showcasing its versatility across genres.
The cloud tank’s significance lies in its role as an early precursor to modern visual effects. Before CGI dominated the industry, it offered a practical and artistic way to achieve stunning atmospheric effects. While today’s technology renders clouds with unprecedented precision, the cloud tank reminds us of the ingenuity and creativity that laid the foundation for modern filmmaking. For tech enthusiasts and film buffs alike, it highlights how far we’ve come while celebrating the charm of yesteryear’s visual wizardry.
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Originally published on Hacker News on 2/19/2026