Invisible Ink


Invisible ink, often associated with spies, can be easily made at home with a few simple household ingredients lemon juice and water. Those spies aren't so tricky now are they! George Washington army used the same idea to send messages in the American Revolutionary war. How does a clear liquid become a readable message? Heat triggers oxidation causing a reaction that makes the juice darker in color.


  • 1 tbs of water
  • 1/4 cup of lemon juice
  • White paper
  • Paint brush or Q tip
  • Bowl
  • Heat source (toaster, candle. etc.)
  • spoon


  1. Pour lemon juice into bowl
  2. Pour water into bowl
  3. Mix water and lemon juice with spoon
  4. Write text on white piece of paper with paint brush or Q tip (make sure enough juice is applied)
  5. let paper dry
  6. Take paper and put it next to or in heat source, make sure your paper does not burn
  7. Wait till text starts appearing to take it away from heat source
  8. You have made invisible ink!


As mentioned in the summary the juice goes through a reaction called oxidation. Why did this happen? Carbon based compounds were absorbed in the papers fibers when the juice got painted on. As the paper is heated those chemical bonds break down, freeing the carbon. As soon as it touches the air the carbon goes through oxidation, making the text darker. What is oxidation? The process or result of converting an element into an oxide; combine with oxygen

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