Joan Hiatt Harlow

How to Send a Secret Messae in Invisible Ink


Have you read MIDNIGHT RIDER? Remember the stationery with no words? If so, you may wonder how Mrs. Gage was able to send invisible messages.

You can make an easy invisible ink by doing this!


Important! Have a teacher or parent help.

What you’ll need:

  1. Real lemon juice – either from a lemon or from a bottle.
  2. A tea saucer or bowl
  3. A small clean paintbrush or toothpick
  4. Blank paper


Pour a small amount of lemon juice into the saucer.

Dip your brush (or toothpick) into the juice.

Now begin writing your secret message on the blank paper.  Be sure to dip often into the lemon juice.

Let your message dry.


To reveal the message:

Have a parent or teacher hold the paper on which you wrote your message, near a light bulb or radiator – just for a short time. (Fluorescent lights won’t work) Don’t let the paper touch the bulb. And BE CAREFUL NOT TO CATCH THE PAPER ON FIRE.

Watch as the heat brings out the message in brown letters.

How does this work?

Lemon juice contains a mild acid, which remains in the paper after the juice has dried.  When you heat the paper, the acid letters turn brown.