Not your annual Easter Egg dying project; today’s Science Saturday will show you how to make a Naked Egg.

egg-poke

A “naked egg” is an egg that has no shell. Right, an egg with no shell. This is not something you normally run across and even when folks are shown a naked egg  they often times  just don’t get the idea that the shell is gone – yet the egg stays intact. You might want to check out the anatomy of an egg to get an idea what we are dealing with.

The shell of an egg (typically a chicken egg) is made up of primarily calcium carbonate. If you soak this egg shell in vinegar (which is about 5% acetic acid), you start a chemical reaction that dissolves the calcium carbonate shell. The acetic acid reacts with the calcium carbonate in the egg shell and releases carbon dioxide gas that you see as bubbles on the shell. The egg insides remain intact and are held together by the two fragile membranes just inside the shell.

Here’s what you need

Let’s get to the fun stuff. In order to make a Naked Egg you will need the following items:

  • Vinegar (at least 16 ounces)
  • A couple of glasses or cups
  • Raw eggs

The process is really very simple. Carefully place the egg in a cup and fill the cup with vinegar so that the egg is completely covered. Don’t worry if the egg floats a bit. Just get enough vinegar in the cup to mostly cover the egg.

An egg soaking in vinegar with part of it’s shell dissolved.

Now the hard part – you will have to wait as the acetic acid in the vinegar begins to react with the calcium in the egg shell. In just a short while, you should see some bubbles appearing on the outside of the egg. These are bubbles of carbon dioxide gas from the reaction. It can take 12-24 hours before a good portion of the shell is removed. A good sign of progress is a white frothy scummy layer on the top of the surface of the vinegar.

After a day of soaking you can carefully remove the egg from the vinegar. I would suggest pouring the liquid into another cup and catching the egg in your hand. Using a spoon to fish the egg out might seem like a good idea, but I’ve seen a few eggs break or get damaged when using a spoon to remove them.

At this point you may be able to literally rub the shell off the egg with your fingers. It will rub off as a white powdery substance. Give it try, just be very careful, you don’t want to break the egg, it’s getting more fragile as the shell is slowly dissolved. Depending on your particular egg, you may already have a naked egg. However, it is best if you fill a cup with fresh vinegar and soak the egg for at least one more day.

After two days of soaking you should have a pretty cool Naked Egg. Notice that the egg is a bit bigger than when you first started. This is because some of the vinegar (and some of the  water in the vinegar) has moved through the membranes to the inside of the egg. The membranes are semi-permeable and allow water to move through them.

You have now had a lesson in osmosis from Imagination Station.

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