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.20170519_165110

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.


In the first test tube is vinegar. In the second test tube is water. In the last test tube is borax. Each test tube has 2 drops of phenolphthalein.



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