As a secret agent, you may need to send messages. But how can you keep your message hidden? Of course, Inge and Magne have the solution.
You need:
• Phenolphthalein: an indicator that is colorless in acidic and neutral solutions, and pink in basic solutions
• A large sheet
• A basic solution, such as lye beads (NaOH)
• A brush or spray bottle
Recipe:
1. Dissolve 0.1 gram of phenolphthalein in 100 ml of alcohol
2. Write a secret message on a large white sheet and let it dry
3. Spray the sheet with an alkaline solution. We used a teaspoon of lye beads (NaOH) in a liter of water
4. The secret message becomes visible in pink
An easier way to make secret writing is to write with lemon juice, let it dry, and then heat it up, either with an iron or in the oven.
Good luck and Merry Christmas!
