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Liquid Sand Hot Tub- Fluidized air bed

Mark Rober · 151.3M views · 2017-11-28 · 9:09

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Overview

Mark Rober builds a hot tub filled with sand fluidized by air blown from below, so that the sand behaves like a liquid. He explains how fluidized beds work and shows people swimming in them.

On Hacker News

HN mentions it as the famous, kid-delighting demo of fluidization, especially in sand battery and industrial process threads.

Recommended by 2 HN people across 2 months · HN mentions 2018–2025

Topics

Everyday physics & science demos3D printing, CNC & maker projects
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fluidized bedmark roberliquid sandphysics demodiy build

What people said

isoprophlex · 2022-11 · Recommendation

No in fact this is a bloody brilliant design: they turn it into a huge fluidized bed reactor and extract the heat with air! See this fun fluidized sand-filled jacuzzi if you're not grokking my too brief explanation: [VIDEO]

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reconbot · 2018-12 · Recommendation

Faked and discovered to include fake reactions that were then removed, are different situations. Mark has been producing high quality educational and entertaining videos that encourage kids to get into science. I have personally watched kids go nuts over his Fluidized air bed experiments, and convince their parents to try it out. [VIDEO] It sucks there was fake content in there, but the device was real and the fake actions removed.

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d--b · 2025-09 · Reference

They probably use the trick where they blow air in the sand to give it "liquid" properties where they need the sand to flow. For those who haven't seen it there is a famous Mark Rober video: [VIDEO]

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Sources

Video by Mark Rober, played through YouTube.

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