Science Experiments for Kids: Invisible Ink

Jill Holtz

November 10, 2011

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In our series of fun science experiments for kids to try at home, kindly provided by The School of Chemistry at NUI Galway, try this Invisible Ink experiment and have some fun with secret letters!

invisible ink

You will need:

  • Lemon Juice
  • Paintbrushes
  • Containers to hold liquids
  • Art paper
  • Iodine solution

What to do:

  1. Paint a picture or write a secret message on the art paper with lemon juice.
  2. Once dry, typically an hour, brush over your painting using the Iodine solution to reveal the picture or message in white with a blue background.

How does it work?

Paper has starch in it, which reacts with iodine to form a blue complex. The vitamin C in lemon juice blocks this reaction, so areas of the paper coated in lemon juice remain white. Scientists use iodine as an indicator to tell whether or not vitamin C is present. If they measure carefully, they can even find out how much vitamin C is present.

You can also use your iodine vitamin C indicator to find out if other juices contain vitamin C. Just paint a patch of liquid onto paper as you did the lemon juice, and coat the paper with iodine solution to see if the patch remains white.

You might want to try milk, white vinegar, and dissolved solid foods as well. Some foods naturally contain vitamin C, and sometimes vitamin C is added to food. To find out if vitamin C has been added, check the ingredient list (note: vitamin C is also called ascorbic acid).

The School of Chemistry at NUI Galway advise that adult supervision is needed for all experiments. The portions of materials used in the experiments should not be increased from that described and mixtures prepared should not be ingested. The full text should be read before starting any experiment.

Did you have a go at making Invisible Ink?  How did it go? Tell us in the comments below!

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Published On: November 10th, 2011 / Categories: School, Things To Do / Last Updated: April 3rd, 2021 / Tags: /

About the Author: Jill Holtz

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Jill is one of the co-founders of Mykidstime and a mum of 2 girls

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