Magic Sand at Steve Spangler Science. Random But Cool: How to Make Bouncy Balls from Common Household Items! I realize that this how-to strays a bit from our normal fare, but goshdarnit, it's too cool not to share!
Maybe it's the overgrown kid inside me or my love of science (have I told y'all I was in the science club in high school?? Geek to the max.), but the idea of making bouncy balls--from scratch--out of regular ol' household items totally intrigues me. Make a Bouncing Polymer Ball - Experiment with Polymers. Introduction Balls have been toys practically forever, but the bouncing ball is a more recent innovation.
Bouncing balls were originally made of natural rubber, though now bouncing balls can be made of plastics and other polymers or even treated leather. You can use chemistry to make your own bouncing ball.