Make Invisible Ink Using Milk

Easy Invisible Ink from the Kitchen

You can use milk as an invisible ink to write secret messages.
You can use milk as an invisible ink to write secret messages. Photodisc, Getty Images
By
Anne Marie Helmenstine, Ph.D.
Anne Marie Helmenstine, Ph.D.
Chemistry Expert
  • Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
  • B.A., Physics and Mathematics, Hastings College
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
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Updated on January 10, 2020

Milk is an effective and readily available form of invisible ink. Write the message with milk, let it dry, and watch it disappear. Here's how to use milk as invisible ink to write and reveal secret messages. Also included is an explanation of how milk works as an invisible ink.

Iodine solution revealing an invisible ink message
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How to Make Your Own Invisible Ink
By Anne Marie Helmenstine, Ph.D.
  1. Dip a paintbrush, toothpick or stick into milk and write your message on paper. You'll be able to see the damp message, but it will disappear once the paper dries.
  2. Reveal the invisible message by holding the paper over a lit light bulb or other heat source.

How It Works

The substances in milk weaken the paper and also may be more susceptible to heat than the paper, so although the message dries clear, the paper weakens and darkens where the milk was applied. Other common kitchen ingredients you can use for invisible ink include lemon juice, baking soda, and even urine.

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Your Citation
Helmenstine, Anne Marie, Ph.D. "Make Invisible Ink Using Milk." ThoughtCo, Apr. 5, 2023, thoughtco.com/invisible-ink-using-milk-607935. Helmenstine, Anne Marie, Ph.D. (2023, April 5). Make Invisible Ink Using Milk. Retrieved from https://www.thoughtco.com/invisible-ink-using-milk-607935 Helmenstine, Anne Marie, Ph.D. "Make Invisible Ink Using Milk." ThoughtCo. https://www.thoughtco.com/invisible-ink-using-milk-607935 (accessed April 26, 2024).