In Australia, the Central Intelligence Agency recently declassified six World War I documents, the oldest held by the agency. Their contents? The ingredients used to create invisible ink.
The ingredients, it seems, are a little more complicated than the ones used in the (seemingly) awesome toys we played with in the 80s. The formulas date from 1917 to 1918, and the documents containing all the information have always been too sensitive to release right up until now. And there were more than one recipe as well: combinations of iron sulphate and potassium cyanide, or rice starch mixed with ink and water were both used. Water, potassium iodate, and tartaric acid were all used to reveal the message.
The documents also reveal more scandalous tidbits: one piece written in 1914 in French exposes a German formula for making secret ink, which suggest French spies had hacked the German’s code. Another document, written by someone in California, suggests using invisible ink to paint messages on bodies and even toenails. Kinda like an oldschool tattoo.
We, however, believe in the old method of tried and true invisible inks…the kind that only requires a few minutes of your time. Plus isn’t it just more romantic to send home encrypted letters while you’re on the road? Nothing says “love” like working hard to read the news from someone overseas.
What you need:
-Swab (i.e. Q-Tip)
-Heat source (i.e. light bulb)
-A sense of humor
1. Mix equal parts water and baking soda.
2. Using the Q-Tip (or swab of choice), use the mixture to write a message on white paper.
3. Let ink dry.
4. To read the message, hold the paper up to the heat source. The writing will turn brown, or catch fire. If writing catches fire, start over.
BONUS: paint over the paper with purple grape juice! The ink will turn a different color.
Take that, CIA. You didn’t need all that fancy chemistry after all and we could have saved you thousands of dollars in sending letters overseas. We found the perfect solution.