It's magic!  It's mystery!  No - It's science.  Teachers and students write secret messages with disappearing ink and then use chemistry to develop and transmit the messages.  Students learn about the properties of characteristic acid-base indicator and extend their understanding of pH and acid - base concepts.  

Concepts:  Acids and bases, pH, indicators

Time Required:  20-30 minutes

Chemicals Needed:  Thymolphthalein indicator solution and sodium 

                                     hydroxide solution