What happens when you put a pin in a balloon?
We have a trick that allows us to put a pin in a balloon and still have the un-burstable balloon.
How does this work?
When a pin normally goes into a balloon, the rubber next to the pin pulls away and the balloon bursts.
We put strips of sticky tape on the balloon and then we stuck the pin into the balloon just where the tape was.
The rubber under the tape couldn't pull away so the balloon didn't burst, and in fact we could push the pin in and out of the balloon where it acted like a stopper. When the pin was taken out a little air could escape through the hole, but when the pin was pushed back in the air stayed in the balloon.