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How to Read a Message Written in Invisible Ink

Invisible ink works in different ways depending on the method used to make the ink. Some spies use baking soda, milk or vinegar to make invisible ink. You can also try other liquids that are high in acid, such as lemon juice, white wine, orange juice or apple juice. The ways to reveal the hidden ink will depend on the method used to encrypt the message. Heating up the paper the message was written on will often display the invisible ink.

Things You'll Need

Iron
100-watt lightbulb

Instructions

- 1
  Heat up the paper the message was written on. To do this, carefully iron the paper with a warm iron or hold the message over a 100-watt lightbulb. This strategy works with invisible ink that was written with milk or juice with a high acid content.
- 2
  Dip a paintbrush or sponge in grape juice concentrate. Paint the concentrate across the page with the invisible ink on it. The message will be revealed if the sleuth used baking soda for the invisible ink.
- 3
  Color over the message with a wax crayon.This will work if the invisible ink was lemon juice or another high-acid juice.
- 4
  Sprinkle salt on the paper with the invisible message. Wait 60 seconds before wiping the salt away. If the invisible ink was written in lemon, orange, or apple juice, the hidden letters will become clear.

Insects & Science