How to Write an Invisible Message

This is a fun little activity that you can amaze your children with. Introduce them to invisible ink, and they'll probably think you're a genius. Show them how to write an invisible message or draw a map to secret treasure using milk or lemon juice. This experiment works because milk and lemon juice are mildly acidic organic materials that remain embedded in the paper after they dry. The dried acids turn dark when they're heated. While the kids probably won't care much about such scientific blather, they'll probably spend the entire afternoon writing and deciphering invisible messages.

Things You'll Need

• 1/4 cup milk or lemon juice
• Cotton swab or paint brush
• White paper
• Heat source such as a 100-watt bulb, candle or toaster

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Instructions

1. • 1

     Pour milk or lemon juice into a small container.

   • 2

     Dip a cotton swab or paintbrush into the liquid.

   • 3

     Write a secret message or draw a map on a piece of plain white paper.

   • 4

     Set the paper on the counter to air dry completely.

   • 5

     Hold the backside of the paper near a heat source such as a 100-watt bulb, lit candle or operating toaster. Don't touch the paper directly to the heat source. Your invisible message will quickly appear as a permanent dark brown stain.