# Deflating inflating balloon

There are two balloons, one is big and the other is small.

With special means, the smaller one is inserted in the bigger one in such a way that the openings of both the balloons are available to inflate them with air.

Then the smaller one, which is literally inside the bigger one is inflated. Later the bigger one is inflated with air and the openings of both the balloons are sealed in such a manner that the smaller one is entirely detached from the bigger one and can move freely around inside the bigger one.

So, at this stage, we have two balloons which are inflated with air and one inside the other (the smaller one being inside the bigger one).

Then the question is - how can we deflate/puncture the inner one without deflating the bigger one (that means the bigger one / outer one should be intact in its shape and size)?

You may use whatever instruments / accessories are needed to achieve this.

There are TWO different solutions possible, depending on the circumstances. Perhaps more solutions can be possible too!

Hint:

During a night / rainy day or anytime for that matter, common house-hold articles particularly stationery articles would come to help.

• The first 5 paragraphs can be reduced to something like, "A balloon is inflated inside a bigger inflated balloon. How do you pop the inner balloon, while not popping the outer balloon?" Aug 27, 2017 at 8:31
• You can just use a 4 dimensional needle. Everyone got one of those lying around. Aug 29, 2017 at 8:25

Here is my take on it:

You could add some clear tape to the outer balloon, and then stick a long needle through both. As long as the needle is in the outer balloon, it will remain inflated. The inner one will pop, since it doesn't have the tape.

• Probably would not need to be clear. Aug 27, 2017 at 2:49
• @PeregrineRook I assume jacoblaw means scotch tape as opposed to, say, duct tape Aug 27, 2017 at 3:03
• Well, that’s my point. Wouldn’t duct tape work just as well as scotch tape? Aug 27, 2017 at 3:07

One way is to

use a magnifying glass and focus intense light on the surface of the inner balloon until it bursts. The outer balloon, if well inflated, may allow enough light to pass through so that the focused light will burn the inner one first. On a clear day may use the Sun, else a strong light source.

• well got the one of the possible answers correct. Good. That covers one of the possible circumstances. How about achieving it during a night / rainy day ?! :-) Aug 26, 2017 at 3:26
• Updated to give what in general is needed in those circumstances - without specific instrument name.
– Tom
Aug 26, 2017 at 3:37
• any common house-hold articles would do. Well I add what type articles as a hint to this question. Aug 26, 2017 at 3:42

One solution, assuming the balloons are different colors

Say the outer balloon is red and the inner balloon is blue. Shine a powerful red laser into the balloon. It should pass through the red balloon, and pop the blue one. Some light will reflect off the red balloon, but enough should be able to get through to pop the blue one.

• Good thought indeed. Not sure if such colored laser helps here. Aug 26, 2017 at 3:41
• the laser trick would work, but powerful lasers are not a common household item. Aug 26, 2017 at 7:12
• I actually did this at a party ½ year ago... Aug 26, 2017 at 13:56
• But the bit about common house-hold articles is only a hint.  The puzzle proper says “You may use whatever instruments / accessories are needed to achieve this.” (emphasis added) Aug 27, 2017 at 2:47

jacoblaw has already given the answer I was going to, so here is a minor variation.

Take a long needle (sharp, smooth, possibly lightly oiled). On the outer balloon, select a spot very near the knotted opening which is where the rubber is least stretched. If you stick the pin through there, it will not pop the balloon, and you can then use the needle to pop the inner balloon.

This should work:

Use a extracorporeal shock wave lithotripsy machine. This pulverizes kidney stones by placing them at the second foci of an ellipse where there first foci is a source of high-intensity acoustic pulses. Arrange things so that a point on the surface of the inner balloon is where the kidney stone ordinarily is. In their unfocused state, the sound-waves will pass safely through the outer balloon but (if carefully calibrated) have enough energy at the focus to pop the inner balloon. (Disclaimer: I don't seem the have an ESWL machine lying around my house, so I have been unable to actually test this. It is at least possible that the focused acoustical pulses would just sort of push around the inner balloon without popping hit).

One way is to

Put a needle carefully inside the smaller balloon before inflating. Inflate both balloons carefully so the needle do not stick the small balloon. After inflating both balloons, shock the balloons hardly, the needle inside the small balloon will stick the balloon and pop it.

• Good, but that alters the pre-conditions of the problem. A nice variant in answers. Also, shaking balloons may not gurantee that the inner balloon gets popped. Aug 26, 2017 at 6:26

This should work as it doesn't deflate the outer balloon.

There are actually balloon stuffing machines that would allow you to do this rather easily. They work by creating a near vacuum in a sealed container which the bigger balloon is in pulling the balloon to the sides of the container. The big balloon is inflated by the air coming in to fill the void created by the vacuum. You can then fill a smaller balloon and seal it and drop it in and tie off the bigger balloon to seal it.
Then if you do not open the container and break the seal destroying the vacuum around the bigger balloon, oh can untie the bigger balloon and it will remain inflated due to the vacuum around it and reach in with your hand and pop the smaller balloon with a sharp object.

• Thanks @rubio couldn't get the spoiler markdown to work off my phone. Aug 27, 2017 at 8:20