We made our first bouncy balls from a store bought kit. They've turned out pretty well. They bounce without falling apart which was something I was a little worried about. My kids managed to make them without creating a huge mess, another thing I was worried about. The crystals come in several fun colors and come with resealable plastic baggies plus two different molds so you can make all kinds of different concoctions. There are supposed to be enough supplies to make 21 different bouncy balls which is enough to make it worth the $10 I spent for the kit IF the supplies stretch that far. We'll have to wait and see.
Next up on the project list is a more involved bouncy ball project found here. Then we will make our own slime. As the household cleaning lady, I'm kind of dreading that experiment. And then last, but certainly not least, we will try making our own silly putty. Part of the idea here is to help the kids realize just how many different things in their world are polymers and help them identify which things are not polymers like metal or brick.