Supersaturate borax in water and then pour off the water into a large-ish cup. Start pouring in some gluePour in lots of glue...the more glue, the bigger the rubber ball.
Enjoy! It was lots of fun and super easy. They don't last forever, but you can bounce them and play with them for a day or two.
Dominic had a blast with these. He was surprised the next morning when his ball was flat as a pancake..... =) He says he loves science! This is our next project!