How to Make Invisible Ink Using Lemon Juice

Sending and receiving secret messages is fun for kids and encourages imaginative play. Here is a very easy way to write and decode messages using homemade invisible ink.

Things You'll Need

• Toothpick, small paintbrush or feather pen (for the feather pen, you will need a large feather and a sharp penknife)
• Lemon juice
• Paper
• Candle

Instructions

1. 

   Use a toothpick or a small paintbrush or some other thin object to write your secret message using lemon juice as ink. If you would like to make a feather pen to apply the lemon juice, use the picture here as guide for shaping the end of the feather.

2. Let the lemon juice dry completely. As it dries it should become less visible. You may want to experiment with different types of paper to see which ones will produce a more invisible result. If your writing is not as invisible as you would like, try again using less juice.

3. To "decode" the secret message, hold the paper over a candle, allowing the paper to become very hot but not burn. The lemon juice contains carbon atoms that will turn black as the paper is heated. As the writing darkens, you will be able to read it.

4. Write a letter using regular ink as a "decoy" letter. Put your invisible writing between the lines or on the edges. Only the person receiving the letter will know that it contains a secret message. Anyone else coming across the letter will think it is just a regular letter.

Tips & Warnings

• Be careful any time you use an open flame. Follow good fire safety precautions when using the candle. Adult supervision would be advisable.