Science Smarts: Top secret messages

By Patty Rooks on January 17, 2026.

It has been a busy week preparing for all of the exciting activities I have in the weeks coming up. I think it is important to have some fun things to mix in to the serious parts of a meeting so everyone has a positive learning experience. This has me looking to the upcoming “holiday” of Valentine’s Day as I incorporate these engaging learning opportunities. I thought I would share one with you this week – it can carry over to your Valentine’s Day activities in the science classroom as well – a spin on an old classic. Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

– Cotton swab

– Lemon juice (fresh or bottled)

– White paper

– Iron

– Small dish or bowl (petri dish)

– Measuring spoon

– Flat, sturdy surface to work on

– Towel

Procedure

1. Measure 5 mL (one teaspoon) of lemon juice and pour into the bowl.

2. Place the cotton swab in the lemon juice. Allow it to get quite wet.

3. Write a message on the piece of white paper. It should be quite wet. It will not be invisible to begin with.

4. Allow the paper to dry.

5. You should not be able to see the message now.

6. Have an adult help you with the next few steps: plug in the iron and allow it to heat up.

7. Place the towel on the flat sturdy surface you are working on.

8. Place the paper on the towel.

9. Carefully iron over the sheet of paper, back and forth several times until you can see the message.

10. BE CAREFUL do not hold the iron on the paper too long it could potentially start on fire. This is why an adult needs to help you!

11. Make messages for all your friends as Valentine’s. BUT make sure you provide them with the instructions on how to read the secret message otherwise they will think you just gave them a blank piece of paper!

What is going on?

In this experiment you created a chemical reaction. The chemical reaction occurred with the lemon juice. As you run the iron over the piece of paper, it becomes quite warm. As it warms, it reacts with the lemon juice and turns your message brown.

Registration for the Regional Science Fair has gone live – it will be open until early March, so if you are thinking of going, do register as soon as possible. As well, the Button Contest has been extended to the end of January – this is a chance to win an amazing cash prize, not to mention, your button design will be featured at the 2026 Regional Science Fair. Visit the praxis website at: http://www.praxismedhat.com/science-fair for more information.

Patty Rooks, senior scientific consultant Praxis Science Outreach Society. Praxis is located in the Community Futures Entre Corp Building at #202 556 Fourth St. SE, Medicine Hat, Alberta, T1A 0K8. For all your science needs, please email praxis@praxismh.ca.

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