You will need:

• Lemon juice
• Paintbrushes
• Art paper
• Iodine solution (dilute a few drops of iodine in some water)

What to do:

1. Write your secret message on some paper using lemon juice.
2. Let your message dry. It will be invisible!
3. When you want to reveal your secret message, paint over the paper with Iodine solution.

How does it work?

Paper has starch in it. Starch reacts with Iodine to form a blue complex. However, the vitamin C in the lemon juice blocks this reaction. This means that your message stays white while the rest of your paper turns blue.

Try writing your message in other juices to see if there is Iodine present in them. You can try orange juice, apple juice, milk and even dissolved food. Some foods, like lemons, naturally contain Vitamin C. Others have Vitamin C added to them. To find out if your food contains Vitamin C, check the label on the back. Vitamin C can also be called ascorbic acid.

Don't forget to take some pictures of your Invisible Ink pictures and send them into us to be in with a chance of winning some great prizes.

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.

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