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!
1. Mix 1/4 cup of baking soda with 1/4 cup of water in a small container.
2. In a separate container, mix lemon juice with a little food coloring.
3. Using a Q-tip or a thin paintbrush, paint a secret message onto a piece of paper.
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!
Source: PBS Parents