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05 Feb '16

Make Your Own Invisible Ink

Posted by Casey McNeil


What we are going to work on today is an experiment where we start with a lemon, add a little science, and get to write in disappearing ink just like we are secret agents!

It may not sound like a lemon would be useful to a secret agent, but with a little bit of science, a lot can happen!  

With a lemon and a few other ingredients, we are going to be able to write hidden messages. All we need are some basic household items and the secret power of lemon juice. First, we will need:

  1. Water
  2. Half of a lemon
  3. Spoon
  4. Small bowl
  5. Single cotton ball
  6. A light bulb
  7. Paper


To write a hidden message, we will:


  • Squeeze some of the lemon juice out into the ball and then add a couple of drops of the water.
  • dip the cotton into the mixture of water and lemon and use it to write a message on the paper Center once the juice becomes dry, it will be completely invisible.
  • once you are ready to read the hidden message comma you can hold it close to a lightbulb and you will see the hidden message appear!


Let's talk about what's Happening Here

When lemon juice is heated, it begins to turn brown because it is an organic substance. If we added straight lemon juice, and didn't dilute it with some water, it would be a bit too dark and still be visible. We had a little bit of water to make it a bit harder to see. 
This way, after adding the water and waiting for it to dry, you wouldn't even know if it was there!  There are other things that you can use to make invisible ink, too. Try talking with your parent and coming up with some different things to experiment with!