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    Home » Invisible Ink

    Invisible Ink

    July 2, 2011 By Emma Vanstone 4 Comments

    This week we are playing detective (In special agent OSO style) and making secret messages with DIY invisible ink.

    You can write messages or draw pictures to each other in secret ink and then make them appear to see what they say!

    (Note: it does require heat to reveal the messages so they would need to be supervised if young!)

    How to make invisible ink

    What you need

    • Half a lemon
    • Water
    • Spoon
    • Bowl
    • Cotton bud
    • White paper
    • Hair dryer

    1. Squeeze the lemon into a bowl. Add just ⅔ drops of water to dilute. This is just to make it clearer on the paper! Your invisible ink is now ready.

    2. Take your invisible pen (your cotton bud) and dip into the ink. Write or draw your message.

    3. Leave to dry.

    4. When you want to reveal your message, you need to apply a heat source. Either hold it near a lamp, iron it or place in the oven. (I found the oven worked best). You do need to watch it carefully to ensure the paper does not scorch.

    5. Admire your message!

    The science of invisible ink

    Lemon juice oxidises (which means it reacts with oxygen) and turns brown when heated.  

    Diluting the lemon juice in water makes it harder to notice the invisible message on the paper.

    invisible ink made from limes

    Other substance to try

    Orange juice

    Lime juice

    Milk

    Vinegar

    Fizzy drinks

    More fun science for kids

    This activity is also part of my Playful Science series, which is full of simple play based science activities for kids.

    Image for a Playful Science series of fun, simple science for kids

    Make a magnifying glass, create your own code and try some more detective based science experiments.

    Red Ted Art also has some great ideas for how to write secret messages!

    image of lemon juice based invisible ink

    Last Updated on March 1, 2022 by Emma Vanstone

    « Magic Milk Investigation
    Adventures with Nature »

    Safety Notice

    Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

    These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

    Reader Interactions

    Comments

    1. Helen R

      July 03, 2011 at 4:48 pm

      This is brill! My toddler is cutting down her nursery days from tomorrow so great to have some simple ideas for educational entertainment!

      Reply
      • Amanda C

        October 02, 2013 at 2:57 pm

        Where does the hair dryer come in at, as a heat source to see or to just dry the paper?

        Reply

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