Bouncy Ball

The cool thing about this project? It takes a few minutes and a few simple ingredients, and you’ve made a bouncy ball! Downside… it’s not a great bouncy ball. At least I haven’t produced a great one after all my testing.

Here’s my detailed process on this… if you’re just looking for a quick summary of the directions, look at my post on Chemistry Mixtures.

I mostly follow the directions on chemistry.about.com (They credit their source as Meg A. Mole’s Bouncing Ball), plus clues from Science Bob, and Home Science Tools.  I also tested, for comparison, different methods, from Paging Fun Moms and PBS Parents. I’ll comment on those below.

Here’s my current recipe with detailed tips.

• Borax Solution: Pour 2 tablespoons warm water and 1/2 teaspoon borax powder into a cup. Stir the mixture to dissolve the borax. [The water needs to be very warm, and you need to stir a while to be sure it’s all dissolved.]
• Pour 1 tablespoon of glue into cup labeled ‘Ball Mixture’. Add food coloring. [I have used Elmer’s all-purpose school glue which yields opaque pastel balls, and Glitter Glue, where the balls turned out a pale shade of the glue color, with subtle hints of glitter, and clear Elmer’s Glue, which is probably the best option – easiest to pour and mix, best results.]
• Add 1/2 teaspoon of the borax solution you just made and 1 tablespoon of cornstarch to the glue. Do not stir. [Tip: this works best if you use a wide dish where you can spread the glue out a bit – sprinkle the borax solution around over all the glue, then sprinkle the corn starch all over that. If you just dump the solution in one place, you end up with part of the mixture interacting great and turning into a ball and other parts where the reaction never happens, and the ball just won’t form correctly. We learned to use a paper snack tray to mix in as cleaning up a dish after making these takes a LOT of scrubbing – it’s easier to throw away a snack tray.]
• Allow ingredients to interact on their own for 15 seconds (the video on about.com says 15 minutes, but it’s really seconds), then stir them together to fully mix. Once the mixture becomes impossible to stir, dust your palms with cornstarch, and take your ball out of the cup.
• Knead the ball by rolling it around in your palms like play-dough. It’s VERY sticky at first. [As you keep rolling it, you’ll feel it start to pull together into a ball. If it’s still really sticky, sprinkle a little more corn starch onto it and keep rolling.]
• Once it’s solidified, bounce it.
• When you’re done playing with it, put it in a Baggie – write name on the baggie!

 

The ball in the close-up picture was made using this recipe, as was the green one in this picture. The one above used glitter glue. The one below used clear glue.

You can see from the photos that the balls aren’t perfectly round, and they’re a little cracked looking. They’ve got a decent amount of elasticity to them, and will bounce about 4 – 8 inches up when dropped on a table. If left to sit overnight, they will flatten out on one side… you can kind of re-roll it, but it won’t be quite as round.

I tested a few alternate methods.

So, the method above is: 1) mix borax & water, 2) mix glue and color; 3) layer glue then borax solution, then corn starch

The red ball / blob in the picture above was from the Paging Fun Moms recipe. It was 1) combine water and borax. 2) combine glue, cornstarch, food color. 3) mix those together. This was a complete fail for me, as you can see from the picture. I was not able to spread the water around enough to come into contact with all the glue / cornstarch goo right away, so it bonded some parts, but not others and failed to form a homogeneous ball. (Note: Kids’ Activities Blog recommends a similar method, but half as much cornstarch. I didn’t bother to test it.)

The blue ball was from the PBS parents recipe. It had way more water and cornstarch than any other recipe. Steps: 1) water, borax and cornstarch, 2) glue and food coloring, 3) mix together. Results: a very elastic, bouncy, semi-translucent ball – most satisfying bouncy ball. BUT it left behind about 4 tablespoons of leftover liquid – waste of ingredients. Also, it did not maintain its shape as well as the other recipe, flattening out a lot.

For the yellow ball, I followed the PBS parents recipe, but with the same ingredient proportions as all the other recipes. Made a good ball, it seemed, but it flattened as soon as you set it down. I left the blue ball and yellow ball the same bag overnight, and they mushed completely, blending into each other, and had to be thrown away the next day.

When we follow the recipe I describe in detail above, you get an OK ball. I think it can be a successful class experiment if you set expectations appropriately. If you tell kids they can make the best bouncy ball ever, they’ll be disappointed in their results. If you ask “what would happen if you combined glue, this powder and this liquid? Did you know you can make a ball that bounces??? Isn’t that crazy?” then they might think the results were cool just for the fact that it makes a ball at all.

We will continue to use this activity, even though it’s not perfect, because it IS interesting.

Make your own silly putty.

Sources I used for ideas: http://www.sciencekids.co.nz/experiments/crazyputty.html  http://www.wikihow.com/Make-Silly-Putty http://www.pbs.org/parents/crafts-for-kids/homemade-silly-putty/.

Supplies: Elmer’s Multi-Purpose Glue (apparently Elmer’s school glue does not work); food coloring, liquid starch (Sta-Flo – apparently Niagara doesn’t work); tablespoon, spoon, dish to mix in, plastic eggs.

1. Put two tablespoons of  glue in a dish.
2. Add food coloring. Mix.
3. Add one tablespoon liquid starch. Stir.
4. Let sit for five minutes.
5. Knead for five to ten minutes.

Note: The recipes I saw often recommend one part glue and one part liquid starch. That led to a handful of liquidy goo that was not kneadable. I added a bunch more glue to my hand and kneaded that in. So, I recommend you start with two tablespoons. When you first start working with this, it’s goo. It takes several minutes of kneading to turn into silly putty. But, in the end, it was a pretty satisfying imitation of silly putty.

But… we decided not to use this in class. Having to wait five minutes mid-process, then having to knead for 10 – 15 was too much to ask our little kids. Plus, the recipe results in silly putty, and many parents can tell you awful stories of silly putty in their carpet or upholstery, and we decided not to send our families home with a product they’d later resent us for.