By Alex, 9/5/2018


Secret agent's egg

Experiments | Chemistry | Secret agent's egg
Secret agent

About this science experiment

During the American Revolutionary War, America's first secret agents risked their lives to help win their independence. Early American spies used all sorts of techniques to hide and transfer important, top secret information. You might've already known about invisible ink, but did you know that they even used hard-boiled eggs?

In this demonstration, we're going to see how, with a simple ingredient sometimes used used to make pickles, we can use a chemical reaction to conceal information below the shells of hard-boiled eggs. Hope you brought your appetite for breakfast!


  • A hard boiled egg
  • A bowl
  • Alum
  • Distilled vinegar
  • Cotton swab
  • A teaspoon
  • Water


  1. In the bowl, dissolve the alum into the vinegar.

  2. Dip the cotton swab into the alum-vinegar solution and write a secret message on the eggshell.

  3. Wash the egg with water so that there's no evidence of the secret message inside.

  4. Carefully peel back the shell to reveal the hidden message written into the egg itself.

Analysis and Conclusion

Hmm... it seems nobody's added a conclusion for this experiment yet. You can suggest one here.



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