Invisible Ink with Lemon Juice

Write secret messages to your friends and family and then let them decode it with any source of heat - like a candle or an incandescent light bulb!

  1. Ages: 5 - 16

  2. <30 minutes

  3. Messy

  4. Grownup needed


Materials you'll need

Step-by-step tutorial

  • Step 1

    Gather your materials!

    Photo reference of how to complete step 1

  • Step 2

    Squeeze the juice of the lemon into a small bowl.

    Photo reference of how to complete step 2

  • Tip

    Some seeds may fall in, but you don’t need to fish them out.

  • Step 3

    Using the cotton swab as a pencil, write a secret message on the paper. Then, let the paper dry completely.

    Photo reference of how to complete step 3

  • Step 4

    Bring your heat source close to the paper and watch as your secret message magically begins to appear!

    Photo reference of how to complete step 4

  • Learn moremagnifying icon graphic

    Lemon juice is mostly made of a variety of sugars, acids, and water. Normally, lemon juice is mostly clear, so when you dilute it even further in water, and paint that mixture onto some paper, you can't see it. However, heating up lemon juice causes some of its sugars to react with oxygen in the air (oxidation), which turns these sugars brown. Acids in the lemon juice can also react with fibers in the paper to make more sugars, which again turn brown in the heat. Your invisible ink might seem like magic, but really, it's all just chemistry.

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