Invisible Ink

  • Due No due date
  • Points _
  • Questions 4
  • Time Limit None


Send secret messages to your friends using just lemon juice and heat!

Your Instructor: College of Science 

Difficulty: Easy

Length of Activity: 15 Minutes 

Parental Warnings: To reveal the message in the end you must get the paper fairly hot. This can be very dangerous so children should not perform this step or get too close. Do not use an open flame to heat up the message or the paper may catch on fire. 


  • Paper
  • Lemon juice
  • Q-tip
  • Heat gun, bare light bulb, or other heat source (not an open flame)
  • Small dish or bowl for the lemon juice

Follow Along Below

Written Instructions (Printable PDF)

  1. Place your lemon juice in the small dish where it can easily be dipped into.
  2. Using a cotton swab as a paintbrush, dip it into the lemon juice and write or draw your message on the paper. Make sure to use enough lemon juice to get the paper wet but not too much that you completely soak the paper.
  3. Let your message dry all the way.
  4. When you want the message or picture revealed, ask an adult to use a heat gun or hot naked light bulb to heat up your paper and reveal the message.