Invisible Ink

Today I tried making invisible ink out of lemon juice. If you would like to give this a go, keep reading 😊

You will need:

A lemon
Water
Spoon
Small bowl
Cotton bud/tooth pick
Paper
Candle* (I used a tea light candle but you could also use a lamp, light bulb or UV light if you have one)

*Ask an adult to help you with this

Method

1. Squeeze some lemon juice into the bowl and add a few drops of water. Mix the water and lemon juice with the spoon.

A few drops of water is about the tip of a teaspoon

2.Lightly dip the cotton bud or tooth pick into the mixture and write a message onto the paper.

Use a cotton bud for thick lines

Use a tooth pick for thin lines

3.Wait for the juice to dry so it becomes completely invisible. Thinner, lighter lines will dry faster.

4.When you are ready to uncover your secret message, heat the paper by holding it above the candle or close to a warm light bulb or lamp. If you are using heat be very careful - ask an adult to do this part with you.

How it looks after being held over the candle

How does it work?

Lemon juice is an organic substance that oxidizes and turns brown when heated. Diluting the lemon juice in water makes it very hard to notice when you apply it the paper, no one will be aware of its presence until it is heated and the secret message is revealed. Other substances which work in the same way include orange juice, honey, milk, onion juice, vinegar and wine. Invisible ink can also be made using chemical reactions or by viewing certain liquids under ultraviolet (UV) light.
Source:  https://www.sciencekids.co.nz/experiments/invisibleink.html

Tips:

• You will need to hold the paper over the heat for 3 - 5 seconds or so before the writing or image appears -be careful not to hold it in one spot too long or it might burn!
• To make it easier to remember where you wrote, you can use lined paper (like refill paper)

I used the cotton bud to draw shapes and the toothpick for writing words. I also used white paper but I wonder if it would work the same way with different coloured paper. You could also try making your own map like I did.

What else can you come up with? Share it with me in the comments below!