A classic project for those rainy sundays – the two most common approaches to making invisible ink in the kitchen:

  • Write a message with lemon juice or, then heat with a lamp/oven/iron to decode (but not burn!) as seen above.
    or

  • Write your message with baking soda + water mixture, allow to dry, and decode by applying grape juice – this text then fades away resulting in a sort of “self-destruct” feature.

Modern data encryption isn’t nearly as fun to demonstrate.

btw – The UK’s MI5 seem to endorse the lemon juice/heat method :D

Related:
Secretmessageglove
Secret Message Glove

In the Maker Shed:
Homechem Crop
Illustrated Guide to Home Chemistry Experiments