Fun Project Idea: Be a secret agent, write with an invisible ink!

February 25th, 2013 : No Comments

Fun Project Idea - e-learning for kids

Fun Project Idea Invisible Ink - e-learning for kids

Make your own invisible ink with Lemon Juice!

Let’s make your very own invisible ink, so that you can pretend to be a secret agent and write secret letters where others can’t read. It’s easy to make invisible ink! All you need is some simple household objects and the secret power of lemon juice.

What you’ll need:

  • Half a lemon
  • Water
  • Spoon
  • Bowl
  • Cotton bud
  • White paper
  • Light bulb


  • Firstly, squeeze some lemon juice into the bowl and add a few drops of water.
  • Next, mix the lemon juice and water with the spoon.
  • Take the cotton bud and dip it into the mixture. Use it to write a message onto the white paper.
  • Wait for the juice to dry so it becomes completely invisible.
  • When you want to read your secret message or show it to someone else, heat the paper by holding it close to a light bulb.

What’s happening?

Lemon juice changes when combined with oxygen and turns brown when heated. Adding water to lemon juice makes it hard to notice when you write it on the paper, no one will know its presence until the paper is heated, then the secret letter is revealed. You can also try this experiment using other substances like orange juice, milk, onion juice, vinegar and honey.

Tags: ,