Send Secret Messages

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In this activity, learners write a secret message in "invisible ink" and then use chemistry to view the writing. Learners will write a message using vinegar or lemon juice as ink and then pass the paper over the lit flame of a candle. The heat from the flame will cause a chemical change in the dried ink allowing learners to read the secret message. Since this activity involves an open flame, adult supervision is required. [Activity is publicly available through a web crawler capture on]

Quick Guide

Preparation Time:
Under 5 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:
1 cent - $1 per student

Age Range:
Ages 8 - 14

Resource Types:
Activity, Demonstration, Experiment/Lab Activity


Materials List (per student)

  • vinegar or lemon juice for ink
  • a toothpick or paintbrush to write with
  • a piece of paper
  • a candle in a holder
  • matches


  • Physical Sciences
    • Heat and Thermodynamics
      • Heat and Temperature
    • Chemistry
      • Chemical Reactions
      • Acids and Bases
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations

Informal Categories

  • Crime Science


To use this activity, learners need to:

  • see
  • see color
  • read
  • touch

Learning styles supported:

  • Involves hands-on or lab activities


This resource is part of:

Access Rights:

  • Free access



  • All rights reserved, Ontario Science Centre, 2011