Try This: Make Invisible Ink from Fruit
Make your own invisible ink to write and reveal secret messages! This science project teaches us some interesting things about chemistry. Let’s get started!
Here’s what you need:
- Juice from a citrus fruit, like lemon juice
- Small cup or bowl
- Cotton swabs or a paint brush
- Paper, white works best
- A heat source, like a hair dryer
- A small container to pour the juice in
Here’s what to do:
1. Pour a small amount of juice into your container. Dip the cotton swab or paintbrush into the liquid.
2. Using the juice and cotton swab, write a message or draw a picture on the paper.
3. Let your message dry fully. It could take up to 30 minutes to fully dry.
4. Once everything is dry, heat the paper with your hair dryer. You could also use a stovetop burner, but you'll want an adult's help.
5. Watch as your message or drawing is revealed!
Citrus juices like lemon juice are slightly acidic. When you applied this to the paper, it weakened the paper. Citrus juices, like all other fruit juices also contain carbon compounds. We don’t normally pay much attention to these carbon compounds until they break down and the carbon reacts with the oxygen in the surrounding air. When this happens it usually results in a slightly unappetizing brownish color. You may have seen this happen to your apple slices when they sat out for a while or a glass or orange juice that was forgotten. This darkening is the result of oxidation — it's basically burnt.
When the juice dried on the paper, it was no longer visible. By applying heat to the paper, the chemical bonds in the dried juice were broken. The carbon reacted with the oxygen in the air and oxidized resulting in a brownish color — and your once invisible drawing or message became visible again!
Can you try other juices, maybe even other liquids that you find in your kitchen? Share with us what works and what wasn’t so successful using #SMOatHome!