Balloon Pen Gun

This instructible will show you how to make a surprisingly powerful pen gun made from only a balloon, a rubberband, and a pen.

Lets get started!

a pen similar to the one shown
a balloon
a rubberband

thats all you need!

First, disassemble the pen. It should look like the picture.
Put the balloon on the end of the pen barrel, and make sure the balloon is not very tight against the pen. 
Secure the balloon with the rubberband.

To fire the pen gun, put the ink cartridge into the barrel