Home >> Science & Nature >> Animals & Science

How to Send Secret Messages

Sending secret messages can be an entertaining, exciting activity or hobby for kids in elementary and middle school. While it is simple to do at home, writing and sending secret messages can also tie into school lessons involving spy techniques in history. Using acidic substances such as lemon juice or vinegar to write on paper weakens the paper. The acid is left behind when the liquid dries and becomes readable when held up to a hot light bulb.

Things You'll Need

Lemon juice or vinegar
Thin, white paper
Cotton swab or toothpick
Small bowl
Envelope
Pen
Required postage

Instructions

- 1
  Fill a small bowl with lemon juice or vinegar. Set out a piece of thin, white paper to write your secret message on.
- 2
  Dip a toothpick or cotton swab into the "invisible ink" and write the secret message on the paper. Let the lemon juice or vinegar dry completely.
- 3
  Fold the paper up and insert it into an appropriately-sized envelope.
- 4
  Send the secret message to the recipient by mail. Alternatively, have a friend deliver the secret message to the recipient or leave it somewhere for the recipient to find.
- 5
  Include a note instructing the recipient how to read the secret message, if desired. The secret message can be revealed by holding the paper up to a heat source, such as a light bulb. The sugars from the invisible ink will turn brown, allowing the recipient to read the message.

Animals & Science