Use some ‘spy’ science and send secret messages using our invisible ink experiment! Wow your family and friends by tricking them into thinking you have given them a blank piece of paper, and then revealing a secret message underneath. This may look like magic but read right to the end to learn the science behind the magic. invisible ink experiment

You will need:

  • Paper
  • A lemon
  • A knife *adult assistance needed*
  • A bowl
  • Cotton buds
  • An iron *adult assistance needed*


  • Cut the lemon in half and squeeze the juice into the bowlinvisible ink experiment
  • Take a cotton bud and dip one end into the bowl of lemon juice
  • Write a secret message on the paper using the cotton bud dipped in lemon juice
  • Let your message dry
  • Iron over the message and it should become visible!

The science bit:

This invisible ink experiment can help us learn about chemistry too! Lemon juice contains the chemical element carbon. When you heat the lemon juice using the iron it makes some of the chemical bonds in the lemon juice break (chemical bonds hold molecules together). When those bonds break the carbon is released, and when the carbon meets the air it turns brown or black.

Why not try:

  • Using a different citrus fruit, does it work with a lime or orange?
  • Drawing a cool picture – it doesn’t have to be a message!
  • Holding it over a lightbulb (make sure you don’t hold it directly on top as lightbulbs can be very hot) – does your message appear like when you used an iron?

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