“A box without hinges, key, or lid; yet golden treasure inside is hid.” This is perhaps my favorite riddle from The Hobbit by J.R.R. Tolkien. The answer is, of course, an egg — the largest cell in the world. Fun Fact: The ostrich holds that record.

So what can we do with an egg that is science-like and fun? Why, dissolve the shell with a mild acid and turn the innards to a rubbery substance, of course. The perfect concoction for any prankster to try!

Materials

• An egg (either cooked or raw… depends on how brave you’re feeling)
• A tall drinking glass
• White vinegar

Procedure 

1. Put your egg into a tall drinking glass.
2. Pour vinegar into the glass until the egg is covered.
3. Put the glass aside so no one drinks from or spills it. It will smell a bit, as vinegar has a strong odor.
4. Let the egg soak overnight. Make
5.  Wait 6 days. That’s a long time, but do it; you don’t want a half pickled egg on your hands.
6. At the end of this time, rinse off the egg and pick it up.
7. You should notice that it feels slightly different than when you started…most noticeably, it is missing the shell and has a weird rubbery feel to it. Shake it. Gently squeeze it.
8. Test out your new creation in the sink by dropping it from a few inches, and then from a few more…
9. You now have a cool creation that can astound your friends and family. Place it back in the egg tray for some hilarity. The possibilities are endless.

Explanation

A chicken’s egg is covered with a shell made of calcium carbonate. That’s a complex arrangement of carbons, calcium, and oxygen. Regular vinegar is made of acetic acid. As you may know, when you mix vinegar and baking soda, you get a strong reaction. The shell is made of the same “carbonate” and will react much like soda, only much less extreme. The little bubbles you see in the water are made of carbon dioxide gas; just like the bubbles from your vinegar and baking soda volcano.

Once the shell is gone, the vinegar will cross over the semi-permeable membrane (through a process called “osmosis”) and slightly inflate the egg. This process also “pickles” the egg, by hardening it up. The toughening of that membrane is what lets you bounce it on the counter, roll it along the floor, and whatever trickery (I mean science) you want to do with it!

Experiment further 

As with all science, the real experimenting takes place after you see the trick. Now that you know how to do this to an egg, what can you change about the experiment? Do all eggs take the same time? Do they all get as bouncy? What about brown eggs versus white ones? Free-range organic versus cage raised … are they different? Does the type of vinegar matter? Keep experimenting!

If you have questions about the rubber egg, or need tips about science fair ideas, visit www.stevedavala.com.