At-Home STEM Activities: Make Your Own Bouncy Ball
Make your own bouncy ball with this easy at-home recipe
A fun all-ages activity, with adult supervision required for younger learners (mess potential!)
Materials (amounts for one ball—multiply to make more balls):
4 ounces of warm water
2 tablespoons Borax (can be found in laundry detergent aisle of most grocery stores)
1 tablespoon cornstarch
1 tablespoon Elmer’s glue
Food coloring (optional but recommended)
2 cups (paper is best, for easy clean-up)
2 spoons or stirrers (we used popsicle sticks, for easy clean-up)
Procedure:
Note: each ball requires 2 cups—you see lots of cups in our photos because we made 4 different balls!
In one cup, mix Borax into warm water until it completely dissolves
In the other cup, mix together glue and a few drops of food coloring
Add the cornstarch and 1/2 teaspoon of your Borax solution to the cup containing glue and food coloring.
Stir the ingredients until well-mixed. They will start to thicken and clump together.
When the ingredients are well blended, and the mixture becomes difficult to stir, pull the entire mixture out of the cup.
Knead and roll the putty mixture in your hands for at least five minutes. We recommend doing this over a sink, because it can be messy!
Note: The putty will be very sticky at first. The more you handle it, the more it will solidify. Removing the moisture helps this process, so you can try squeezing out excess water with your hands or a paper towel.
When the putty starts to feel firm and rubbery, roll it in your hands until it forms a smooth ball. You’re all done!
What’s happening?
This activity relies on a chemical reaction between Borax and Elmer’s glue. Boric acid (B-OH) groups on the Borax molecules form chemical bonds with acetate groups on the glue (polyvinyl acetate) molecules, such that two glue molecules are held together by one Borax molecule. This process is called polymer cross-linking. It makes a long chain of molecules which stick together when handled and have flexible, rubbery properties. The cornstarch helps to bind the molecules together so that they hold their shape better.
Tips
Keep in mind that your homemade ball will not be as bouncy as a manufactured rubber ball—the fun of this activity is more in the process than in the end result
Play around with the proportions of Borax, water, glue, and cornstarch in your mixture. What happens when you add more of one and less of another? A “drier” mixture will result in a more “rubbery” ball
If there is excess liquid in the bottom of the cup when you have mixed all the ingredients together, don’t try to integrate this into the putty. Pour out or dispose of the liquid, and only knead together the ingredients that have linked together into a solid mass
Try putting your putty in the freezer for 15 minutes and then rolling into a ball; this can make it easier to work with
Your ball will only remain solid temporarily. As your ball sits, it will collapse or “melt” into a flat pancake shape. Make sure you do not leave the putty on carpet, upholstered furniture, clothing, or other soft materials!
Prolong the lifespan of your ball by storing it in wax paper, a sealed Tupperware dish, or a plastic “Easter egg” with two halves…anything to keep it from drying out. Even if the ball collapses, you can pull your putty out and knead it into a ball again and again!
