| by Kenneth Chase | 100 comments

Liquid Sand Hot Tub- Fluidized air bed

I’m sitting in a hot tub filled to the brim with solid sand. (laughter) This is one of the coolest things ever! If you take a tub of sand like this and then add air in JUST the right way, it basically becomes a liquefied soup. (music) In science, this is known as a fluidized bed. It’s used in industrial applications such as powder coat painting or in grain silos to make sure that the grain flows smoothly to the outlet. (music) With air on the top surface is nearly frictionless. It’s like an air hockey table. (music continues) And then when you cut off the air, it freezes everything exactly where it’s at. (music continues) So, today I’m going to show you how to make a simple version like this yourself. And then because I became curious what it would feel like to be fully immersed in something like this… We made a hot tub sized version. As you can see from the sixty-year-old video from the Royal Institute of Science, this demo isn’t exactly new. I’ve wanted to build one for a long time, But you can find literally NO information online on how to make one like that. So I started combing through a bunch of patent drawings for massive industrial sized fluid beds, And I noticed that instead of one big inlet, they all had a bunch of small holes to deliver the air. So starting with that in mind, it still took us 25 failed versions before we arrived at this design. As you can see it’s just a bunch of half-inch PVC pipes arranged sort of in a ladder. But the key is to drill two 1 millimeter holes 90 degrees apart from each other and then do a bunch of those spaced to 25 millimeters apart. Then you glue all the pipes together, and just make sure you orient the holes down so that will keep the sand from getting in. And then you just seal off the container with some hot glue. And then fill your container with either fine sand or we found glass beads worked really well. And you can power with a small air compressor like this, or you could just rent a large nitrogen container like this for about 30 bucks, and that’ll give ten minutes of run time. As usual, I will put a link to all of the parts I used the build in the video description. So my buddy Ken can had an old broken Spa on his backyard which we decided to put to good use. (music) (laughter) It just stops, and you’re like locked in place. It’s like a weighted blanket on every surface of your body. (laughter) Ahhh! (music) Now that it was tested and ready, in my ongoing quest to be the favorite uncle… pew pew pew pew, Ahhh!, (screaming) I decided to surprise my nephews with it. (fizzing noise) woah, WOAH! AHHHHHHHHH! (laughter) (music) (laughter and screaming) But before we get to swimming in sand, let’s talk about the science behind a fluidized bed. Wait wait, don’t click away if you think science is boring. If you’re new here, You should know that my approach to science is similar to velociraptor hunting patterns. I try to bring people in with a catchy thumbnail or a cool thing to see, and then when they least expect it… rawr… clever girl, velociraptor shrieks Admittedly, the analogy breaks down a little at the end, but if you promise to hang with me for the next two minutes, I promise to try and walk the delicate line between trying to make things simple to understand, without oversimplifying or being condescending. Fluidization is just when you have enough upward air so that the force of the air pushing on each grain of sand is equal to the downward force of gravity or weight. And when that happens on any individual grain of sand, it hovers in equilibrium like this. You can think of forces acting on an object like a tug of war. If an object is in equilibrium, That means there’s a tie, and it doesn’t accelerate in either direction, just like in a real tug of war if the sides are even. However, if you add Stone Cold Steve Austin to this side that will make it totally unbalanced and will start to move this way, Which is actually what happens if you accidentally turn the air up too high. As a fluidization occurs in that sweet spot where the sand particles hover in equilibrium, Which makes them easy to move around. This is also the reason sometimes you’ll see pools pumped with air to cushion the landing for the divers. Now you notice that some stuff floats in the sand and other stuff sinks. This has to do with the buoyancy force, which is a function of the density of the surrounding fluid and the volume of the object itself. Whenever an object exists in a pressure gradient, there are forces from pressure pushing in on all sides, but they push a little bit harder the deeper that you are. Which is why it hurts more to be the bottom guy in a dog pile, or it hurts your ears more the deeper you dive in the pool. And this makes sense because the deeper you dive the more water there is above you pushing down. And if you add up the size and direction of all those arrows, a bunch of stuff cancels out and you’re left with one net force pointing upwards. THAT is the buoyancy force. And if your buoyancy force happens to be greater than your force from gravity, you float. And if your buoyancy force happens to be less than the force from gravity, you sink. Now, we usually think of buoyancy with water, but you can think of things like helium balloons being buoyant in our atmosphere. So here’s a trick question: which of these has a higher buoyancy force? It’s actually… the rubber ball? Buoyancy force has nothing to do with the density of the object, just the volume. So since the rubber ball takes up more space, it has a higher buoyancy force. But, you might object then why does the rubber ball sink and the balloon floats? Remember, it’s a tug of war. The rubber ball sinks because the force from gravity on the thick rubber skin and the air inside, is bigger than the buoyancy force. But for the balloon, even though it doesn’t have as big of a buoyancy force compared to the ball, It still floats up, because that buoyancy force is bigger than the weight arrow from the helium and the thin rubber shell. And the helium will keep rising like a ball floating up from deep in a lake. And then it will eventually hang out where the density of the atmosphere is roughly equal to the density of the helium of the balloon, Because that’s where the tug-of-war becomes equal. Phew! We made it through! Now back to my nephews. (giggling) (screaming) (laughter) (screaming and laugher) Aw! No, oh no! I can’t get it out! Get it! (Nephew): I can’t! (Other Nephew): Got it! Turn it off! Ok, cut it! AH! (Laughter) Christmas is coming, and with the help of Casper who happened to support this video, I got your back. And with the exception of a Bob Ross chia pet, what could possibly be better than the gift of a good night’s rest? With Casper, you order online, and then they’ll ship it right to your door for free and it shows up in a box like this, And then you open it and it magically expands to actual mattress size! We totally love ours, and with over 20,000 reviews with an average rating of 4.8 stars on sites like Amazon, There’s a pretty good chance you’ll love it, too. And they’re also affordable because you cut out the sweaty price haggling commission based middleman who works at a typical mattress store. And you could try it out for a hundred days, and if at the end of that you’re like meh… They’ll come pick it up for FREE, you get all your money back, no questions asked. So, skip the crowded mall this year and finish your Christmas shopping right now by going to Casper.com/MarkRober and using promo code mark Rover for $50 off any mattress. Merry Christmas! And thanks for watching. (Epic Outro Music)


Cyper Nexus

Oct 10, 2019, 8:17 pm Reply

Forbidden milk

My Memes Dank

Oct 10, 2019, 11:15 pm Reply

Sooo quick sand?

My Memes Dank

Oct 10, 2019, 11:18 pm Reply



Oct 10, 2019, 11:46 pm Reply

Yoooooo. I want an uncle like that ?

Fuzion & Snipezz

Oct 10, 2019, 11:51 pm Reply

I wish this guy was my uncle?

Amazing Plays

Oct 10, 2019, 12:03 am Reply

Who thinks this reminds you of air hockey


Oct 10, 2019, 3:01 am Reply

0:37 looks like the hand to my furry costume (I’m a Scorpion)


Oct 10, 2019, 5:14 am Reply

Nephews other Uncles: I got yall some gum
Mark Rober: Hey guys wanna play in sand pit that is like a pool
Nephews: Yay!!!!
Other Uncle: (╯°□°)╯︵ ┻━┻

Sarotin Sahir

Oct 10, 2019, 12:30 pm Reply


Unknown:clever girl…..

Me : dangit.. Fricking science


Oct 10, 2019, 6:42 pm Reply

What would happen if you did it on the beach

Akasha Dream

Oct 10, 2019, 10:35 pm Reply

So Great! 😀


Oct 10, 2019, 2:00 am Reply

Now if a spa can make money off it.

cacapoop poopy

Oct 10, 2019, 2:32 am Reply

1:46 playing wwe be like

gnom ed

Oct 10, 2019, 2:51 am Reply

Unbalanced forces and balances forces is what he saying i I think


Oct 10, 2019, 4:20 am Reply

Imagine it breaking while ur inside it :O

pro EYE

Oct 10, 2019, 5:23 am Reply

Why do I have the same hair dryer as him


Oct 10, 2019, 8:18 am Reply

this dude is just making sure that hes the best uncle ?. love it

Grant Fuerst

Oct 10, 2019, 8:53 am Reply

If your dog is annoying than. Make this and put it in and stop it so it sufocantes ?

Umaraniya Jaimin

Oct 10, 2019, 9:19 am Reply

You are in you have been warned I watch ed

Unbeatble TV

Oct 10, 2019, 10:29 am Reply

What if you do it in the beach?

Saniya Ammar

Oct 10, 2019, 10:35 am Reply


ZJ Gaming

Oct 10, 2019, 1:00 pm Reply

No one:
Mark's cousin: i peed


Oct 10, 2019, 2:07 pm Reply

Oh how much I would love to have you as my uncle and/or be an uncle like you!

Oscar Marley Hopes

Oct 10, 2019, 7:05 pm Reply

dang so satisfying

timothy tran

Oct 10, 2019, 8:47 pm Reply

1:35 I saw a rainbow ?

Kelvin Dang

Oct 10, 2019, 11:41 pm Reply

It’s quick sand bruh

Kelvin Dang

Oct 10, 2019, 11:41 pm Reply


Kelvin Dang

Oct 10, 2019, 11:41 pm Reply


Kelvin Dang

Oct 10, 2019, 11:41 pm Reply

And it’s a bath

chirag agrawal

Oct 10, 2019, 5:15 am Reply

The choice of your beats are sick

Brody Dodgin

Oct 10, 2019, 6:37 am Reply

I didn't know this was a try not to get satisfied challenge?


Oct 10, 2019, 7:58 am Reply

Boo how!


Oct 10, 2019, 11:21 am Reply

Looks so satisfying

Ankit Dhiman

Oct 10, 2019, 1:27 pm Reply

Bhajjjj bhosdi KK

Matthee Tjem

Oct 10, 2019, 2:54 pm Reply

I just see a rainbow

our crew

Oct 10, 2019, 6:49 pm Reply

Who saw the rainbow at the side of the screen at 1:36 pls wait you WILL see it! (◍•ᴗ•◍)

Opwz Stuckey

Oct 10, 2019, 12:00 am Reply



Oct 10, 2019, 2:02 am Reply

Can u sell it and make more

Giorgi Tvalmixelashvili

Oct 10, 2019, 2:44 am Reply

Loooool about the science part

Kade Anderson

Oct 10, 2019, 6:20 am Reply

Rip that bird


Oct 10, 2019, 11:26 am Reply

*turns off heat while I'm still under the sand*

Starberrymilk suffocated in a wall

A Typical Dino

Oct 10, 2019, 12:43 pm Reply

My parents like mark rober because he teaches us yay

Stefanie Smith

Oct 10, 2019, 1:01 pm Reply

Did you see the rainbow? 1:35

Vincinho 8

Oct 10, 2019, 2:37 pm Reply

What would happen, if you mix water in it?

Queen Gang

Oct 10, 2019, 3:02 pm Reply

Why is this so satisfying ??

Joni da gamer

Oct 10, 2019, 5:43 pm Reply


Dad of the Roblox owner

Oct 10, 2019, 7:17 pm Reply

Thats my paradise

Duck Robot

Oct 10, 2019, 9:57 pm Reply

He is definitely the favorite uncle now

••ControllerTheNightDragon•• .-.

Oct 10, 2019, 12:06 am Reply

Can we get an F for that pigeon that was drowned in grain at 0:55

Jake Munoz

Oct 10, 2019, 2:22 am Reply

So cool I wanna try that

W Jy

Oct 10, 2019, 8:56 am Reply

Oh no it's physics ;-;

Dhae Zaky

Oct 10, 2019, 1:00 pm Reply

Is that how the sandworm swims?

Liam At Play

Oct 10, 2019, 1:12 pm Reply

LOL ???????

The Infinity Channel

Oct 10, 2019, 4:23 pm Reply

5:11 Mark watches studio C


Oct 10, 2019, 4:36 pm Reply

Sand turns into water when you add air.
Aight imma head out.

Akio Kuro

Oct 10, 2019, 5:06 pm Reply



Oct 10, 2019, 5:16 pm Reply

No ones talking about how all that sand probably got in the kids mouth…

evan choper Benard

Oct 10, 2019, 5:28 pm Reply

Did any one see the rainbow on 1:35

evan choper Benard

Oct 10, 2019, 5:31 pm Reply

Is his hand the ball 3:40

evan choper Benard

Oct 10, 2019, 5:33 pm Reply

That's scary on 4:38

Bendo The ink demon

Oct 10, 2019, 8:11 pm Reply

So quick sand

Logan Reid

Oct 10, 2019, 9:39 pm Reply

Who else saw Eggs!??? Mmmm

Det hedder Negerboller

Oct 10, 2019, 12:09 am Reply

Omg so cool

Rexy Boi 727

Oct 10, 2019, 12:18 am Reply

“ It basically becomes a liquified soup”

Isn’t soup already liquified??

ColonCapitalD _

Oct 10, 2019, 12:26 am Reply

What if your in it for 10 minutes and you forget to refill the canister and it runs out while your under

Fishingsports YT

Oct 10, 2019, 12:44 am Reply


Pandaisdunb 35

Oct 10, 2019, 1:10 am Reply

Someone:Why you make a mess?
Mark Rober:I was testing.

Payne860/ Geomaster20

Oct 10, 2019, 1:22 am Reply

4:28 I dont care. You would make a good science teacher.

Little Scientist Ujwal

Oct 10, 2019, 1:24 pm Reply

Congratulations you got chance in "YOU HAVE BEEN WARNED"

Cameron Butterfield

Oct 10, 2019, 1:58 pm Reply

U not boring

Mineslof Cat

Oct 10, 2019, 2:57 pm Reply

Do you want your soup crunchy, pr soupy?

the_dudete 123

Oct 10, 2019, 9:16 pm Reply

This is the real way sandman was created.


Oct 10, 2019, 9:34 pm Reply

Every one of his videos are try not to get satisfied challenge

Nilachal Vaidaya

Oct 10, 2019, 10:33 pm Reply

Who saw rainbow at 1:35?

Like if you did

Christian Rendon

Oct 10, 2019, 11:20 pm Reply

Who saw a rainbow on the left at 1:35

Bryson Berent

Oct 10, 2019, 11:55 pm Reply

Enter Sandman intensifies

chris .,

Oct 10, 2019, 2:09 am Reply

well,…. that's sand in your shorts(!)

TheBackup ONE

Oct 10, 2019, 2:14 am Reply

It looks like milk


Oct 10, 2019, 4:23 am Reply

So it’s quick sand than

Death Dodger

Oct 10, 2019, 6:04 am Reply

Is sand wet?


Oct 10, 2019, 7:57 am Reply

A rainbow appear at


Oct 10, 2019, 12:01 pm Reply

The science part makes me think of that one part of the Wasp Factory …
Please use this… Science you speak of to determine how thst woyld go in real life?!

Spice _61

Oct 10, 2019, 2:41 pm Reply

Look to the left of your screen you can see a rainbow! w

Gavin McAfee

Oct 10, 2019, 3:26 pm Reply

1:35 RAINBOW !!!!!!!!!!!!!!!!!!!!!!!!!!!

Hope Veal

Oct 10, 2019, 9:20 pm Reply

They’ll have sand in places they didn’t know they had!


Oct 10, 2019, 9:24 pm Reply

To old still love it


Oct 10, 2019, 12:08 am Reply

I can’t imagine how much fun this would be.
I’m so jealous.
If I you agree,
Click dere

SealyPlayZ xxX

Oct 10, 2019, 12:10 am Reply

Liquid sand

XuanMai Nguyen

Oct 10, 2019, 12:39 am Reply

The objects who in the liquid sand
Their playing


Oct 10, 2019, 8:25 pm Reply

1:34 I see a rainbow

Alvane Playz

Oct 10, 2019, 11:41 pm Reply

So many sand wasted


Oct 10, 2019, 12:19 am Reply

Something very cool is the rainbow like water but sand and it makes a rainbow please like so mark can see

Anna Davis

Oct 10, 2019, 12:41 am Reply

Who else wants to feel that sand


Oct 10, 2019, 8:17 am Reply

Is it just me or does anyone else care about the bird that went under?

Tanisa Samaddar

Oct 10, 2019, 6:49 pm Reply

Is no one going to talk about the bird

El MariaJIN El MariaJIN

Oct 10, 2019, 12:18 am Reply

Yo that is satisfying to the BRIM


Oct 10, 2019, 12:40 am Reply

To everyone wanting to be his nephew I can be your Uncle ( ͡° ͜ʖ ͡°)

len the lion

Oct 10, 2019, 4:27 am Reply

At 4:45 I noticed that he had a studio c sticker and wondered why and then I remembered that he was featured on one of there vids and can someone reply the link for people reading I’m on a phone so I can’t copy and paste

Devan Steinke

Oct 10, 2019, 5:48 am Reply

How are you so smart

Alexe Jade Official

Oct 10, 2019, 6:13 am Reply

I'm googling it after this but what is quick sand lol

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