Making invisible ink with lemon

If your child has ever seen the film ‘National Treasure’ with Nicholas Cage and Diane Kruger, they will have seen a coded, unseen map on the Declaration of Independence. To reveal its secrets, they used lemons and heat to unveil the code. It was really cool! The secret code was made with invisible ink. You and your child could make your own invisible ink and write your own hidden codes and messages to each other. Here is how to make invisible ink with lemon:

What you will need:

  • Half a lemon
  • Water
  • Cotton buds (alternatively, you could use a paintbrush, toothpick, or feather)
  • A lamp or candle (or a hairdryer will work)

First, squeeze the lemon juice into a bowl, add a few drops of water and stir. Get a cotton bud (or one of the alternatives) and dip it into the lemon and water mixture and write a message on a piece of white paper. Allow the invisible ink to dry, and you will notice your message disappear.

Once dry, take your paper and place it over a lamp bulb or candle. From the heat of the bulb or flame, your message will reappear. Be careful if using a candle that the paper doesn’t get too close to start a fire.

It’s as simple and as quick as that! You have made invisible ink with lemon.

If you want to think of some ways to engage your child in something fun at home, use this invisible ink method to create a treasure map. Create your invisible riddles and clues that they must find around the house with a prize at the end.

Our ‘Science up your Sleeve’ box has many fun little science projects, from making water disappear, turning milk into plastic, vanishing flames and more! All the things you will need for these little science experiments are included in the box. So have some fun and learn some cool tricks along the way.

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