A Hillhouse student’s eyes widened as he applied grape juice and heat to what appeared to be a blank piece of paper — but instead held a secret message in invisible ink, written as part of a course ...

This isn’t like the invisible ink of our childhood. That’s probably a good thing. We doubt an LED bulb makes enough heat to develop our old secret messages. [Ranomona’s] ink doesn’t use ...

Need to send secret messages? Dr Chris and Dr Xand have a brilliant experiment for spies in training... Create your own invisible ink! Shh! Step 1: Put on your rubber gloves and lab coat (or old ...