Science Smarts: A simple ‘secret’ message

By Patty Rooks on March 29, 2025.

What an exciting week we had with the 50th annual Regional Science Fair. We may have broken some records with how many amazing students we had in attendance from all over southeastern Alberta. On to the next step as the two grand prize winners are busy preparing their projects for the Canada Wide Science Fair, which is fast approaching.

If you see them, make sure to wish them luck! I know many of the young scientists are still tired and recovering from such an amazing weekend, so I thought we would keep the experiment simple this week, but also useful for April Fool’s Day. Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

– Tincture of iodine

– Small jar

– Small bowl

– Medicine dropper

– Paint brush (small for writing)

– Paint brush (large for “painting” iodine solution on the paper)

– Lemon juice

– White paper

– Safety goggles

Procedure

1. Put your safety goggles on.

2. Add 60 mL (1/4 cup) of water into a jar. Add 10 drops of iodine. Set aside.

3. To make it easier, pour a little bit of lemon juice into a bowl. Using the small brush, write your message in lemon juice on the paper.

4. Let the lemon juice dry on the paper so it is invisible.

5. Give your message to a special person.

6. In order to read the message, the person needs to brush the paper with the mixture of iodine and water you made earlier.

7. Observe what happens!

What is going on?

In this experiment you were basically performing a chemical test. When you brushed the paper with the iodine mixture, it reacted with the lemon juice and you should have been able to see the “secret message.”

Patty Rooks, senior scientific consultant PRAXIS, “Connecting Science To The Community.” Contact Praxis at praxis@praxismh.ca, http://www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook. Address: 12 826 11th Street SE, Medicine Hat, AB, T1A 1T7 Phone: 403-527-5365, email: praxis@praxismh.ca.

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