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Invisible Ink

Here’s a crafty mystery that even Sherlock Holmes wouldn’t be able to crack! How do you make invisible ink with four of the most basic supplies? It’s quite simple, really, but it’s sure to provide you and your students with a lot of excitement and a bit of intrigue. The best part is not only are they practicing their secret agent skills, but your students will also be eager to showcase their handwriting and creative thinking abilities through this simple project.

Invisible Ink

What you will need

  • Lemon juice or milk
  • 1 Toothpick
  • Printer paper
  • a pencil
  • Lighter and/or candle

How to make it

  1. Pour the lemon juice or milk into a small bowl. This will be your ink!
  2. Dip the toothpick into the ink and use it like a pen to write on the paper.
  3. Let the message dry.
  4. This step must be done by an adult! Make sure to have water available just in case the paper catches on fire. Carefully hold the paper up to a heat source (lighter or candle) and watch carefully as the words suddenly appear out of nowhere!
  5. Your kids could create secret messages and practice their reading and writing skills!
Step 1. You'll need some lemon juice! (Or milk.)

Step 1. You'll need some lemon juice! (Or milk.)

Step 2. Dip the toothpick in the lemon juice.

Step 2. Dip the toothpick in the lemon juice.

Step 3. Write your secret message!

Step 3. Write your secret message!

Step 4. Heat up the paper (carefully)...and watch your secret message appear!.

Step 4. Heat up the paper (carefully)...and watch your secret message appear!.

The fun isn’t over yet! Once you have experimented with the milk and lemon juice, ask students why they think it worked as an invisible ink. The explanations are sure to be colorful and creative. If they have exhausted all possibilities, you can explain that there is a chemical reaction that occurs between the paper and the liquid when it is exposed to the heat. The lemon juice and fat in milk both have acidic qualities. When the liquids dry and are then exposed to a heat source, they oxidize to reveal the brown color. In simpler terms, the acids eat away at the paper and leave you with the brown coloration that you see.

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