During the American Revolutionary War, the first US spy ring was created, the Culper Spy Ring. Early American secret agents used all sorts of techniques to hide and transfer secret information. You might've already known about invisible ink, but did you know that early spies also used hard-boiled eggs?

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