How to Make Invisible Ink With Milk and Lemon Juice

Written by casandra maier
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  • Introduction

    How to Make Invisible Ink With Milk and Lemon Juice

    Whether you are teaching an elementary science class, or you are simply looking for a fun activity to experiment with, making invisible ink is simple and entertaining for both children and adults. You can use invisible ink to exchange secret messages and explore the way elements react with paper, chemicals and heat. Using basic household items, write a message that will remain invisible as it dries and will not reappear until the proper reaction occurs. Use milk or lemon juice to make an invisible ink that reappears when heated.

    Milk or lemon juice can be used to make invisible ink. (Container of milk. Plastic milk bottle image by L. Shat from

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    Pour a small amount of milk or lemon juice into a small bowl. You can use fresh squeezed lemon juice or store-bought lemon juice.

    You can use bottled lemon juice or fresh squeezed lemon juice to make invisible ink. (impressing lemon's juice image by Maria Brzostowska from

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    Lightly dip the end of a cotton swab into the milk or lemon juice. Write a message on a piece of paper using the dipped cotten swab. Do not over-saturate the paper, as the paper will wrinkle.

    Use the end of a cotton swab to write your message. (Cotton swab image by lefebvre_jonathan from

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    Allow the paper to dry completely. At this point the message will be invisible.

    Once dry, the message will not be visible on the paper. (paper image by max blain from

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    Hold the paper with the invisible message over a 100 watt light bulb. Do not rest the paper directly on the bulb. The message in milk or lemon juice will reappear in brown. If you used lemon juice to write your message, you can make the message reappear by lightly spraying the paper with red cabbage water, because red cabbage water is an indicator for acids.

    The message will reappear when the milk or lemon juice reacts with the heat from the light bulb. (light bulb image by jovica antoski from

  • Checklist

    Things you will need

    • Small bowl
    • Milk
    • Lemon juice
    • Cotton swab
    • Paper
    • 100 watt light bulb
    • Red cabbage water
    • Spray bottle
  • More information

    Tips and warnings

    To make your own red cabbage water, chop one red cabbage into small pieces. Simmer the pieces in a pot of water until the water turns a deep purple colour. Always have an adult assist with reappearing ink to avoid burns.

    Never use halogen lamps when trying to make the message reappear, as it can potentially start a fire.

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