People have been using invisible ink for 2,000 years. Sending notes or secret messages is a fun part of childhood that we all remember. Even though it's not allowed, passing notes in classes was a pivotal part of what I did in class. Now, I'm not condoning passing notes and class time should be used only for learning, but outside of class here is a fun experiment to make your screen notes a little more advanced.
Materials
Cardstock
Measuring spoons
3 cups or small bowls
Spoons
Q-tips or a brush
Old newspaper
Paper Towels
The Experiment: There are two different experiments with two sets of materials. They both use the materials above but have some extra materials listed below.
Method One Materials
Water
Lemon juice
Iron
Method Two Materials
Baking soda
Water
Turmeric and rubbing alcohol
Method One Experiment
Mix the lemon juice and water in a small bowl. Dip the Q-tip in the lemon water mixture and draw a design on the cardstock. Be careful not to soak the paper too much.
Wait twenty minutes to make sure the paper is dry.
Ask an adult to help you use an iron to iron the paper. Be very careful because the iron will get hot.
Your message should show up in a brownish color.
Method Two Experiment
This is similar to method one but with some new materials.
Mix baking soda and water in a small bowl.
Use a Q-tip to draw a message or design on a piece of cardstock. Make sure not to soak the water too much.
Wait for it to dry completely.
Mix the turmeric and water in another small bowl.
With a Q-tip spread the turmeric water solution all over the paper and your message. The message should start to appear orange.
Now that we all feel like spy kids, let's talk about why this happens.
This experiment is heavily dependent on the material's Ph level. I talked about this in my puking pumpkins experiment but let's do a recap.
The position of these substances on the pH scale determines their classification. The pH scale measures the acidity or alkalinity of a substance and assigns it a numerical value. This scale is frequently utilized for quality control in water treatment facilities and other industries. Understanding the pH of a product is crucial, as it can significantly impact its reactions and overall effectiveness. A base, like baking soda, releases or binds hydrogen ions and can break down fat molecules. Specifically, baking soda is effective for cleaning because it can decompose fats and hair. In contrast, an acid like vinegar releases hydrogen ions when diluted in water. This property also contributes to its effectiveness in cleaners as acids react with limescale and various minerals. When combined, acids and bases produce a reaction that generates carbon dioxide.
The lemon is an acid and when it reacts with the paper it breaks down the fibers of the paper. The lemon’s carbohydrates are absorbed into the paper and carbohydrates hate heat. When you put the iron on the paper it releases carbon which oxidizes when it comes in contact with the air. This reveals your secret message in a brown color.
The baking soda solution is a base and reacts to reveal your message but in a different way than the lemon juice. The baking soda is absorbed into the paper but disappears when it dries. Turmeric is a way to test the pH of substances so when it's painted on an alkaline surface it changes color and shows the secret message.
There are so many ways to write secret messages with acidic and alkaline materials so I encourage you to try some more materials. Remember to always ask an adult to help you with the iron and with handling materials like lemon juice that could hurt your eyes. Be careful and have fun!
Work Cited
“Secret Messages With Invisible Ink! | STEM Activity.” Science Buddies, https://www.sciencebuddies.org/stem-activities/invisible-ink#whathappened. Accessed 27 October 2024.
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