Secret Spy Messages

  • Lemon Juice
  • Paper
  • Paintbrush/Cottonswab
  • Hairdryer/Iron

This is a simple activity that can be used to communicate top secret messages to your friends! You can even post them to your camp friends that are too far away for you to see this summer!

  • Squeeze lemon juice into a bowl
  • Dip a utensil like a thin paint brush or cotton swab into the lemon juice and paint your picture or write your top secret message onto a piece of paper
  • Allow the lemon juice to dry into the paper so no trace can be seen
  • When fully dried use a hairdryer to heat up the page and reveal the secret message

Note: it is also possible to use an iron to reveal the message but a parent must be present for this part. It is also advised to not use the steam setting and rather the dry heat.  

There is no hurry to reveal the message - this works due to science as the lemon juice is acidic and heat causes the particles of lemon juice to break up and oxidise! Oxidation causes things to change colour such as a bike chain that turns rusty and brown!)

This activity is brought to you by Camp Northland, an overnight camp based in Haliburton, Ontario with a 100+ year tradition of creating memorable summer experiences for children and teenagers from Southern Ontario.

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