If you saw the Mr. Culpeper (106) episode of TURN (now called Washington’s Spies) you will recognize the subject of this post: Steganographic eggs! These were a tactic used to pass information between Revolutionary War-era spies. “Ghost Message” eggs, as they are commonly called, are very cool and can be made with just a few simple household items! The “Ghost Message” technique was first described in 1558 by Giambattista della Porta in his book entitled Magia Naturalis. After seeing this on the show and reading about it on the show’s blog, we decided that we had to give it a try ourselves. Armed with a carton of eggs and a bottle of vinegar, we set off on our exciting adventure as a secret, secret squirrel!
The first thing that you need to do isn’t really all THAT exciting.
1. Fill a pot with water and boil it.
2. Add the eggs to the boiling water, cover and let cook for 20-25 minutes.
3. With a metal spoon, mix up a solution of equal parts alum (hydrated potassium aluminium sulfate) and white distilled vinegar, both are available at your local grocery store.
4. When the eggs are finished being boiled, remove them from the water (be careful of hot water, pans and steam), allowing them to dry before the next step. (As you can see, two of our eggs gave their lives in brave service to this blog, and we salute them for their sacrifice).
5. Dip a paintbrush, q-tip, toothpick, etc. into your “ink” solution and write your secret message on the egg shell, then let it dry.
6. I’d like to make a note here that the method used in the show of holding the egg up to a low burning fire for 10 seconds with your bare hand DOES NOT WORK. This requires intense heat and/or light to make it work correctly. Using a long pair of tongs to hold the egg over a direct flame or a light source with at LEAST a 200wt bulb for no less than 10 minutes is required. Whichever way you choose to expose the egg to the heat/light, be careful!!! The eggs will be very hot when your 10 minutes is up!
7. Once the egg has cooled to a temperature that allows you to touch it without burning yourself, crack it open and look for the message! We tried several batches and were only able to make ONE EGG work the way that it should have. What happens during the chemical reaction is that the vinegar is basically disintegrating the shell. When the shell starts to go away (but not enough for you to notice it outwardly) the alum leaks through and leaves the word impressed on the inner egg white.
This is a really cool trick and I think children would love to do this little activity. I feel it’s obvious, but I’m sure for legal reasons I should say it: ALWAYS supervise children around things that are HOT! Do not allow them to put their little hands or faces in or next to a fire! Also, DO NOT EAT THESE EGGS, they are bad for you! If you would like to try another cool egg trick, submerge and uncooked egg in a glass of white vinegar for a few days, then remove it. The shell will be completely gone, but the inner membrane will be intact and you will be able to hold the egg in your hand and to see inside of it (sort of) without it breaking!