Invisible ink

Invisible ink

We know that phenolphthalein will turn pink if you drip 2-3 drops into a chemical that is base. That gave me an idea of how to make invisible ink.

Things you’ll need: phenolphthalein solution, white paper, Q-tip, and ammonia-based glass cleaner (like Windex)

1. Put a few drops of phenolphthalein onto a Q-tip. Use the Q-tip as your pen to write a simple message (like “hello”).
2. Let the paper dry. You cannot see the message.
3. Once the paper is dry, spray it with a few squirts of glass cleaner. The message will appear again in purple.

Phenolphthalein is a PH indicator that is pink in the presence of bases. Since the window cleaner is a base, it reacted with your phenolphthalein writing to change color and appear visible. Look at this picture below.