Homemade Invisible Ink Experiment
Here we show you how to create homemade invisible ink and how to write and reveal your hidden message. We also reveal the science behind the magic...
Difficulty: Easy | Time: 5—10 minutes
What you need:
1 tablespoon baking soda
2 tablespoons water
Paper
Your choice of a writing tool.
This could be a paintbrush, cotton bud or quillPurple grape juice
Two small bowls
What to do:
To make the invisible ink use a small bowl to mix the water and baking soda. Stir together.
Write words on your paper with your ink and choice of magic ink pen (look below for ideas of what to write.)
Wait for the ink to completely dry and then brush off any excess baking soda.
Now paint over the paper with grape juice and watch your writing or picture magically appear!
What to write:
Experiment with different writing tools and write the name of the tool in the invisible ink.
We tried a cotton bud, a thin paintbrush and a feather which we fashioned into a (not very good) quill.
What other objects could you try writing with?Write a joke or question with a normal ink pen and then write the answer in invisible ink for someone to reveal.
Make a treasure hunt around your garden and write clues in invisible ink. Have grape juice ready at each point so that the players can uncover their clues.
The Science Behind the Magic:
The invisible words appear because of a chemical reaction between the grape juice and the baking soda.
The grape juice is an indicator that shows us if an alkali (also called a base) is present by turning blue.
What is an indicator?
An indicator is something that can change colour depending on whether it is in a base or an acid substance.
Scientists often use litmus paper as an indicator. This paper turns blue when in a base and red in an acid substance. It can also turn green which shows the substance is neutral (not an acid or base).
In this case purple grape juice is a natural indicator which turns bluish purple/black when reacting with a base. The invisible ink we have created is made up of baking soda (which is a base) and water (which is neutral). Therefore, when the grape juice indicator reacts with the invisible ink it turns it dark blackish blue.
Other Natural Indicators
There are other juices such as red cabbage, beetroot juice and tea which are also natural indicators. A fun indicator plant is the Hydrangea, when it is in acidic soil the Hydrangea flowers will be pink or red and when it is in alkaline soil they will be blue.
Extra Experiments
Test out the grape juice indicator by adding lemon juice or white wine vinegar to a mix of grape juice and baking soda. You should see it fizz and bubble and then change from bluish purple to a light pink or reddish purple. It can make a mess so work on an easy to clean surface.
Happy experimenting!
Did you give it a go?
Did you try making your own Invisible Ink? Send us a photo of what you created, and some words about what you learnt, and you’ll go into the draw to win a mystery “Upstart DIYer” prize.