Introduction: Tennis Balls in a Bottle (How-to!)

Picture of Tennis Balls in a Bottle (How-to!)

I love a good puzzle.

Some of my favorite kinds are strictly conceptual, meaning that once created, these objects require you to simply look and think about them. You can hold them, shake them, examine them . . . but you can't physically disassemble the completed object.

I have several such items at my house that just sit on a shelf and cause visitors to scratch their heads and say ". . . wait . . . how did you . . ?"

Spoiler Alert:

In this instructable, I'm showing how I put two standard tennis balls into a completely unaltered bottle.

For any readers that enjoy puzzles and are up for a challenge: stop reading, examine the photo above, and try to duplicate it on your own. To you brave souls, I bid you good luck and happy problem-solving; come back when you've got it and let me know how it went!

For everyone else, read on to see how I did this.

Step 1: Bottle and Balls

Picture of Bottle and Balls

The bottle I'm using is a carafe I got at a local thrift store for 50 cents. The narrowest internal part of the neck is about 1 5/8" (4.1 cm) in diameter.

The balls are standard tennis balls and are about 2 5/8" (6.6 cm) in diameter.

Step 2: Considerations

Picture of Considerations

I encountered some funny things as a result of the fact that I used generic Walmart tennis balls for this.

From whatever manufacturing process is used to make these tennis balls, they're left with these little flaps on the rubber seams which distract people into thinking something is amiss where there really isn't. Also, the lack of any branding or logos leads people to think these tennis balls are "trick balls" or something, which they are not.

Because of this, I recommend using higher quality tennis balls for the sake of presentation. Whatever tennis balls you use will work exactly the same, however.

Step 3: Cut

Picture of Cut

Use a sharp hobby knife to make a 1/4" incision in each ball.

Note that when you press the ball a certain way it opens up. When you release, the cut disappears.

Step 4: Fold

Picture of Fold

On the opposite side of the ball from the incision, press that half of the ball inward to create a bowl shape.

Then fold the ball in half as shown. It's critical that the cut be facing outward at this point.

This may take some effort and ninja-like grip strength.

Step 5: Wedge

Picture of Wedge

The ball is now wedged into the bottle.

Compress the ball as much as possible before you begin to wedge it in. With a moderate amount of pressure the ball should plop down into the bottle.

If you're concerned that the bottle neck may break from the outward pressure of the compressed ball, you might want to wear gloves, long sleeves, and goggles. (I did not do this, but the thought certainly crossed my mind.)

Step 6: Wait

Picture of Wait

Because the cut is on the outside of the folded ball, it is being somewhat held open which allows air to return into the ball.

If you wait a few seconds the ball will re-inflate by itself.

If it does not, you can prod it a little with a long dowel until it does.

Step 7: Fluff

Picture of Fluff

If upon close inspection the incision is visible, use a long wire with a bend on the end to fluff up the fibers around the cut to mask it.

This little implement was made from a straightened piece of wire with a couple of L bends on either end.

It is useful for many things.

Now just repeat the process for the second tennis ball.

Step 8: Done!

Picture of Done!

That's it!

It's seems simple and obvious . . . once you've seen how it was done. Can you think of another way you could do this, perhaps with a bottle with a smaller neck?

If you're up for a tougher challenge, check out my Deck of Cards in a Bottle instructable.

Thanks for reading!


LuiSousa made it! (author)2017-08-30

Já executei ...

NiftyNiffler (author)2017-07-17

How do you get the tennis balls out again?

seamster (author)NiftyNiffler2017-07-17

You'd have to break the bottle :)

NiftyNiffler (author)seamster2017-07-19

Ok... So I shouldn't use any old, valuable museum vases then!

(not that I was planning to...)

Caironater (author)NiftyNiffler2017-07-29

Alternatively, just set them on fire, mwuahahaha. Of course, this may break your museum-grade vase anyway, but at least you'd get some pyrotechnical fun out of it.

NiftyNiffler (author)Caironater2017-07-30


seamster (author)NiftyNiffler2017-07-19

Definitely not! : )

Thanks for the quick reply!

How cool is this project.... SO FUNNY!!!

; D

JorjaSue13 (author)2016-12-04


Wirelessgeo14 (author)JorjaSue132017-04-04

yeah it is

Wirelessgeo14 (author)2017-04-04

this is pretty good. I'm going to do it

flaming robot (author)2016-12-01

cool! where did you get the bottle?

seamster (author)flaming robot2016-12-01

The bottle I used is a carafe I got at a local thrift store for 50 cents.

SophiesFoodieFiles (author)2016-10-20

hahahahahaha! A fun project! Cool!

KarenK116 (author)2016-09-29

I love it :)

macsigo (author)2016-09-12


Niii Pawww (author)2016-09-06

Nice trick!

GabrielK32 (author)2016-08-23

Why not raising the pressure to ~5 atmospheres? You would not need to cut the ball.. :)

earaiz (author)GabrielK322016-08-23

You can take the ball and the bottle for a dive to a depth of near 30m and down there you could easily insert the ball into the bottle. This is exactly what my diving instructor used to show me the effects of high pressure under water; he took a tennis ball with him and showed it to me at the bottom. When you return to the surface the ball recovers the original shape.

No holes needed! :)

SteveH24 (author)earaiz2016-08-23

You should see what happens when you something to the bottom of the ocean. Our crew on a research vessel would send down all sorts of stuff to be miniaturized by the pressure. None of it returned to its original shape at the surface; a mile of ocean creates a great deal of pressure :)

richardvannoy (author)SteveH242016-08-23

When I was aboard a submarine, there was a large barrel shaped container (with holes in it) that was used to store our mooring line. The funniest result from putting stuff in there was a standard styrafoam cup. After one cruise, it looked like a thimble.

cas46per (author)richardvannoy2016-09-03

That would be cool to see

Rehcaet (author)richardvannoy2016-08-24

What sub were you on and when? I was swapped for a Week in 1972 From the USS Cone, (Distroyer) to the USS Daniel Webster what a difference from seeing the sky at anytime I wanted to not seeing it for seven days. We made a deep dive I don't know how deep, although they put a can of coke in some kind of hatch then flooded it and pumped the water out. What can was left, a very small disc of aluminum. The pull top blew out and the can crushed flat. Wow.

FunLife3315 (author)Rehcaet2016-09-01

full or empty? full is impossible to crush. (nearly)

They have low mass, so they compress easily. Try balloons. Just wait for the Ka-Blump/Boom.

FunLife3315 (author)SteveH242016-09-01

mmm yeah. a bit annoying if you drop something accidentally

itsmescotty (author)SteveH242016-08-29

the neoprene hood on my KMB-10 is totally flat from repeated deep air and gas diving, used to be 1/4".

StephenM206 (author)earaiz2016-08-27

very good!

seamster (author)earaiz2016-08-23

That's pretty cool! Alas, I don't scuba dive and all I had was an xacto knife ;)

For anyone that does dive, though, that would be a cool object to make and have.

SteveJ113 (author)earaiz2016-08-23

That's what I was thinking... When I saw the picture, I didn't really care to make the puzzle, but I thought "Cool - He's going to show me how to make a quick and easy pressure chamber to shrink those balls!" :-)

FunLife3315 (author)GabrielK322016-09-01

the egg in a bottle trick.... if you use a vacuum cleaner, it could work. (not with the non-robust egg. same principle though)

JRDUKIE (author)2016-08-31

That is really cool! Nice trick.

EthelS7 (author)2016-08-31

Have you ever heard of Harry Eng? Go to He put some phenomenal things into bottles.

seamster (author)EthelS72016-08-31

Yes, he certainly made some amazing things. In my decks of cards instructable (linked in last step), I did a whole step about Harry Eng and impossible bottles, and actually shared that same link.

richardvannoy (author)2016-08-28

I was stationed on 4 submarines:
SS340 was where we experimented with objects being crushed on deep dives.

Probably every sub that has gone to design depth after commissioning or yard period had a string party where a string is attached across the diameter of the boats interior and the crew newbies are amazed at how much slack is generated. I was on 640 class boats then built LA class at EB

sbelectrics (author)2016-08-23

Rather than squeeze the ball, could you not suck the air out with a hypodermic needle and a vacuum pump? The ball should collapse under atmospheric pressure to ease insertion. The blemish would then be completely invisible and the ball would be fully usable if removed from the bottle.

ksexton1 (author)sbelectrics2016-08-23

the problem then would be, would the ball reinflate on it's own? In any case, the ball, which was pre-pressurized when new would not have the bounce it started with.

MadCraftwoman (author)ksexton12016-08-28

If the needle were long enough, in theory, you could insert the needle, suck out the air while squeezing the ball to collapse it. Work the ball into the bottle with the needle still inserted, then reinflate the ball through the needle before pulling it out.

mona.blake1 (author)sbelectrics2016-08-23

Great idea!

halegd (author)2016-08-23

I've seen a hard cooked, peeled egg get pulled inside a bottle that is more scientific than this. You get a bottle with a mouth just smaller than the egg. Drop a lit match inside the bottle then put the egg on top. When the match goes out, it has taken all the air out of the bottle, the lower pressure inside the bottle and the air pressure around the egg pushes the egg into the bottle.

TJLee089 (author)halegd2016-08-26

Not hardly! Air is 78% nitrogen, which doesn't change. The oxygen (21%) combines with carbon and/or sulfur to form CO2 and/or SO2. No change in the moles of gas. If this works, it is likely because the air is heated, allowing some gas to vent. When it begins cooling, the egg likely forms a seal, allowing a vacuum to form in the bottle, pulling in the egg.

MadCraftwoman (author)TJLee0892016-08-28

It does work, but yes, for the reason you explained, not because of any change in mass.

kepeb (author)2016-08-27

Two things I don't understand.

Why did you want the balls in the glass?

And how do you get them out?

MadCraftwoman (author)kepeb2016-08-28

1. To make people wonder how you got the balls in the carafe.

2. You don't. That's not the point of the project. See 1, above.

iceng (author)2016-08-28

Take them underwater to 90 feet deep that's about 3 atmospheres to collapse the balls enough to enter the bottle through the neck.

BTW tennis balls are pressurized to 14 PSI and com in a 14 PSI container.

Freezing a ball would harden the ball and it would crack the rubber if aggressed upon.

Micronathan (author)2016-08-23

Just wondering.. suppose I freeze the balls ( tennis that is ) would it not help to contract the air inside and help squeeze them in the bottle ?

wcamammoths (author)Micronathan2016-08-27

It wouldn't work. To calculate expansion/compression, you must use the kelvin temperature scale. Room temperature is about 300k and your freezer is about 270k, so the ball would only be 10 percent smaller.

KiaW2 (author)wcamammoths2016-08-28

I ❤ scientific thinkers! I kinda figured it wouldn't work but didn't know how to explain why. Given the size decrease was more drastic, wouldn't that distort the ball when/if it expands to its normal size?

About This Instructable



Bio: I got an old sewing machine when I was just a kid, and I've been hooked on making stuff ever since. My name is ... More »
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