Christmas Citrus Science

by Amy Sullivan (check out her website at

Though creating invisible ink might sound hard, it’s not! Get the ingredients below and follow these steps to make your own secret message. Then make it appear!

What You Need

  • Baking soda
  • Water
  • Measuring cup
  • Dishtowel
  • White paper
  • Two oranges (or your favorite type of citrus fruit!)
  • Two paint brushes
  • Two bowls
  • Damp paper towels for clean up


  1. Mix ¼ cup (60 mL) of warm water and ¼ cup (60 mL) of baking soda in a small bowl. The mixture will be thick. This is your invisible ink.
  2. Think of a secret message. Try writing a single letter or word first. Then, work your way up to a longer message.
  3. Dip the paintbrush in the baking soda mixture. Make sure to get
    lots of it on your paintbrush.
  4. Paint your secret message on the white sheet of paper.
  5. Set the paper aside to dry. This may take up to ten minutes.
  6. Peel the skin off the oranges and squeeze juice from the oranges
    into another bowl.
  7. Gently touch the white paper with the invisible message to see if it is dry.
  8. Place a dishtowel under the white paper.
  9. Grab the clean paintbrush and dip it in the orange juice. Then gently swipe the paintbrush over the page.
  10. Your secret message is now revealed!
  11. Now that you have practiced, try writing a longer message. Maybe write a secret message to someone in your family!

How does this science experiment work?

The invisible message appears because of an acid-base reaction. That means the acidic orange juice reacts with the baking soda, which is a base.


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