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 clothes) because turmeric can ...
Once her words had dried, they became invisible. But, to ensure her professor didn't put the essay in the bin, she left a note in normal ink saying "heat the paper". The professor, Yuji Yamada ...