How to Build a Pool of Jello You Can Swim In

TL;DR

A swimmable Jello pool can be made by heating water and gelatin above 160°F, transferring it into the pool in layers, and cooling each layer overnight without freezing it. The finished gelatin is firm enough for belly flops, but movement is difficult, and direct sunlight gradually turns the lower layers into a softer, slimy mixture.

Transcript

This is the world's first ever actual pool of Jello. And while it may look simple, it's actually a very difficult engineering challenge to pull off. As proof, If you Google Jello pool, you will either find bad CGI, or a handful of videos of people who tried to do this, but it really didn't work out. So today we're gonna answer possibly the longest ... Read More

Key Insights

• The gelatin mixture became firm whenever testing raised its temperature above 160°F. This experimental threshold determined how the full-scale batches were prepared and made consistent heating one of the project's central engineering requirements.
• Freezing ruined the gelatin during small-scale experiments. The team therefore needed nights cold enough to provide refrigerator-like cooling but not so cold that the pool would freeze, creating a narrow weather window near the end of April.
• Six 55-gallon drums provided the heating capacity needed for the project. Each drum had a custom propane burner underneath and a welded spigot on its side, allowing large batches to be heated and released into the pool.
• Gravity transferred the hot gelatin mixture from the drums into the pool. The barrels were deliberately positioned above the pool so their potential energy could move the liquid without requiring a separate pumping system.
• Layered filling improved the pool's ability to lose heat. The plan called for adding an average of 10 barrels per day over seven days, exposing each new layer to cold night air before more hot mixture was added.
• Convection cooling accelerated heat removal from the pool's surface. A swamp cooler continuously replaced the warmer boundary layer of air above the gelatin with fresh cold air, similar to blowing across a hot cup of soup.
• Direct sunlight gradually reduced the firmness of the lower gelatin layers. By the middle of the day, the pool had become softer, and repeated belly flops, bowling-ball impacts, and continued use caused further breakdown.
• Swimming in the gelatin was possible but physically difficult. The material entered swimmers' noses and ears, resisted movement, and felt slimy and slippery, while still remaining firm enough initially to support recognizable belly flops.

Questions & Answers

Q: How can you make a swimming pool filled with firm Jello?

A firm gelatin pool can be made by heating water and gelatin powder above 160°F, transferring the hot mixture into a pool, and cooling it without allowing it to freeze. The project used six heated 55-gallon drums and added an average of 10 barrels daily for seven days. Cold night air and a swamp cooler removed heat from each layer until the mixture set.

Q: Why is building a full-size Jello pool difficult?

Building a full-size gelatin pool is difficult because the entire mixture must first become hot enough for the gelatin reaction and then cool enough to set. Boiling and refrigerating a small dish is straightforward, but a pool contains far more heat energy. The project required custom heating drums, layered filling, weather monitoring, convection cooling, and a carefully selected seasonal window.

Q: What temperature does gelatin need to reach to become firm?

The project's small-scale experiments found that the gelatin reliably became firm as long as the mixture became hotter than 160°F. That observation established the heating requirement for the full pool. Six 55-gallon drums with custom propane burners were used to reach the necessary temperature before the hot mixture was released through welded spigots and transferred into the pool.

Q: How was an entire pool of gelatin cooled without refrigeration?

The pool was cooled by combining cold night air, layered filling, and continuous airflow from a swamp cooler. The team added an average of 10 barrels each day for seven days so every layer could release heat overnight. The swamp cooler replaced the warm air directly above the surface with fresh cold air, increasing convection and helping the mixture become firm.

Q: Why did the Jello pool need a specific weather window?

The pool needed nights with refrigerator-like temperatures but no freezing conditions. Small-scale experiments showed that freezing ruined the gelatin, while insufficient cooling would leave too much heat in the pool for it to set. Temperature measurements beginning in January, combined with historical plots, identified a roughly three-week opportunity near the end of April for completing the project.

Q: Can a person actually swim in a pool of Jello?

A person can enter and move through a properly prepared gelatin pool, although the experience is not like normal swimming. Movement is difficult because the material provides resistance, and its texture feels slimy and slippery. The gelatin can also fill the swimmer's nose and ears. Early in the day, the pool was firm enough for people to perform belly flops.

Q: Why did the Jello pool become softer during the day?

Direct sunlight gradually reversed some of the firmness in the pool's lower layers. As the day continued, warmth from the sun softened the gelatin, while hours of belly flops, bowling-ball impacts, and general activity physically broke it down further. The pool remained usable for play, but its texture became much less solid than it had been in the morning.

Q: How could a future Jello pool stay firm for longer?

A future version could use a heat-exchanger pipe system beneath the pool's surface, similar in concept to the system described for freezing indoor ice-skating rinks. Such a system would continue removing heat after the gelatin had set and could reduce softening from sunlight. The creator also suggested possibly adding a little sugar, although the original mixture intentionally contained none.

Summary & Key Takeaways

• The project required six months of planning, small-scale experiments, and careful weather monitoring. Testing showed that the gelatin mixture reliably became firm after exceeding 160°F, while freezing ruined its texture. A three-week period near the end of April offered the required combination of refrigerator-like nights and warmer daytime working conditions.

• Six 55-gallon drums, each fitted with a custom propane burner and welded spigot, heated the water and gelatin. The elevated drums allowed gravity to move each batch into the pool. An average of 10 barrels was added daily for seven days, giving the hot layers time to cool overnight.

• The completed pool supported belly flops and allowed people to move through the gelatin, although swimming felt difficult, slippery, and slimy. Direct sunlight, repeated impacts, and hours of use gradually broke down its firmness. A buried heat-exchanger pipe system could help a future version remain solid for longer.