Invisible Ink

This project is half art, half science, and all fun! Just write a message or draw a picture in lemon juice or baking soda invisible ink, then reveal the hidden message by rubbing the paper with flowers.

  1. Ages: 3 - 11

  2. <30 minutes

  3. A little messy

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Materials you'll need

Step-by-step tutorial

  • Step 1

    Gather the materials to make your secret flower messages.

    Photo reference of how to complete step 1

  • Step 2

    Start by making your secret message juice. In one small bowl, pour a little bit of lemon juice. In another small bowl, mix up a big scoop of baking soda with just enough water to make it a liquid. You want a lot of baking soda to get a good color-changing effect.

    Photo reference of how to complete step 2

  • Step 3

    Using a paintbrush or cotton swab, paint your secret message or drawing on the paper. You can just draw a picture, or write a secret note. Or, write a riddle in pen, and then write the answer in the invisible ink.

    Photo reference of how to complete step 3

  • Tip

    You can use both the lemon juice and the baking soda in the same drawing if you like. The lemon juice and baking soda will turn different colors.

  • Step 4

    Let the paper dry for at least an hour or so, until all the water has evaporated and your message is invisible.

    Photo reference of how to complete step 4

  • Step 5

    When you're ready to reveal your secret, rub a flower over the surface of the paper. The smudge will change colors wherever you painted with the lemon juice or baking soda.

    Photo reference of how to complete step 5

  • Step 6

    Rub over all your painted papers with the flowers to reveal your messages and drawings.

    Photo reference of how to complete step 6

  • Tip

    Lemon juice and baking soda aren't the only liquids that work. Test out other liquids (like vinegar) and see what you can find.

  • Learn moremagnifying icon graphic

    The secret here is that the flowers act as pH indicators, changing color in an acid or a base. By using both an acid (lemon juice) and a base (baking soda), you can create a painting that reveals two different colors when you rub the flowers over it. We had a great time experimenting with our flowers, since different flowers create different color changes. Definitely worth the sacrifice of a bouquet!

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