Need to pass along an important message on paper without having it accidentally discovered by your archenemy? Using very common household products, you can easily whip up an invisible ink recipe and write out your secret message with the solution. All the recipient needs to do is heat up the paper using a stovetop of light bulb, or brush the surface of the paper with a simple iodine mixture to read the message.
Illustrated below are three simple methods for making your own invisible ink. Spy glasses not included.
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