Make your own invisible ink
Keep your important detective messages hidden from those around you with this simple experiment.
You will need:
- Half a lemon
- Water
- A spoon
- A bowl
- A small paintbrush
- White paper
- A pen
- A lamp or hair dryer
1. Squeeze some lemon juice into the bowl, add a few drops of water and mix.
2. Use the paintbrush to write a message on the white paper.
3. Wait for the juice to dry so that it becomes completely invisible.
4. Write something else onto the white paper as a decoy.
5. When you are ready, heat the paper to reveal the message. You could do this by holding the paper close to a lamp, radiator or even a hair dryer!
How does it work?
The carbon compounds in lemon juice are colourless at room temperature, therefore invisible.
When you heat the lemon juice a chemical reaction takes place. The heat breaks down the lemon juice causing carbon to be released. That carbon reacts with the oxygen in the air, turning the lemon juice a darker colour.
The scientific name for this process is oxidation. It is the same process you see when you cut a piece of fruit and it turns brown after being left in the air for too long!
More experiments?
Other natural ingredients that react to heat in the same way as lemon juice include vinegar, orange juice, honey and milk. Perhaps you could try making invisible ink with these too and decide which is your preferred method?
