When an acid comes into contact with baking soda, a chemical reaction occurs and carbon dioxide is formed. This reaction creates many different fun visual effects for kids to explore, but one of them is revealing a secret message made out of invisible ink! Make your very own invisible ink with some baking soda and water and reveal the message with an acidic mixture (we used lemon juice) for a fun craft plus science activity rolled into one!


  • paper
  • baking soda
  • water
  • a Q-tip or paintbrush
  • lemon or lime juice and food coloring (or grape juice concentrate)


    1. Mix 1/4 cup of baking soda with 1/4 cup of water in a small container.

    II Baking Soda Water


    2. In a separate container, mix lemon juice with a little food coloring.

    II Lemon Juice Food Coloring

    3. Using a Q-tip or a thin paintbrush, paint a secret message onto a piece of paper.

    II Paint Ink On

    4. Allow the painted secret message in Invisible Ink to dry completely.

    5. Paint over the invisible ink with the lemon juice mixture and watch as the secret message is revealed!

    II Acid Mix on Top

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