This week's challenge is to write a message using invisible ink!

Try these no heat recipes at home - 

 

1. Milk and Pencils

You will need:

• cotton buds or toothpicks
• whole milk
• paper
• a sharpened pencil
• sand paper

 

Write it: Use a cotton bud or toothpick to write your message with whole milk (must be whole or at least 2% – won’t work with skimmed). Let the paper dry completely.

 

Read it: Rub the graphite (black part) of a sharpened pencil on some sand paper over the message so that a graphite powder falls onto the paper. Gently rub the graphite over the paper until your message appears.

 

How it works: When your message dries on the paper, most of the milk evaporates but the fat stays on the paper. Graphite sticks to the fat more than the paper to reveal the message.

 

2. Wax Resist

You will need:

• a white crayon
• watercolour paints
• paper
• water
• a paint brush

 

Write it: Write your message with a white crayon.

 

Read it: Paint over the message with watercolours – darker colours like red, green or blue work best.

 

How it works: Wax repels water. This is why wax paper is so useful – it can’t get wet. Here the watercolour paints will not stick to the white crayon drawing and your message is easily visible.

 

3. Acids and Bases

You will need:

• baking soda
• water
• paper
• a cotton bud, sponge or paint brush
• grape juice

 

Write it: Mix 2 tablespoons of baking soda with 2 tablespoons of water. Use a cotton bud or toothpick dipped in the mixture to write your message. Let the paper dry completely.

 

Read it: Use a cotton bud, sponge or paint brush dipped in grape juice to paint over the message.

 

How it works: The baking soda, a base, reacts with the grape juice, an acid, to produce a different colour on the paper.

 

Good luck Scientists!

Let me know which invisible ink recipe you prefer.