​The Secret Messages That Fooled The Inquisition

Giovanni della Porta was an Italian polymath and scientist back in the 1500s, when agents of the Inquisition were locking people up, including his friends. When he needed to get messages to them, he came up with an ingenious solution that involves writing secret codes inside an egg.

della Porta came up with a method that you can make from kitchen ingredients, although one of those ingredients, alum, is quite rare. Alum is a compound that gets its name from the aluminum in it. It includes potassium, sulfur, and hydrogen, and is used in different forms for many purposes. You can buy potassium alum as a pickling spice, although it has fallen out of favor lately because aluminum compounds have been linked to Alzheimer's disease.

Anyways! Dissolve as much potassium alum as you can in a little bit of vinegar, and paint the mixture on a hardboiled egg. It helps if you leave the mixture under a lightbulb after your painting. Next, wash off the compound, and give the egg to whoever you want to share your secret with. Porta smuggled the eggs past jailors during the Inquisition. When the egg is cracked, the message shows up on the egg white. The vinegar dissolves some of the calcium carbonate in the egg shell, and the alum stains the white.

As for eating the egg? If you use the pickling spice, all the ingredients should be edible. However, if you're concerned about the aluminum, you can still feel good about the fact that you outsmarted the Italian Inquisition.

[Via Ghost Message Egg, Bizarre Labs, The Code Book]