Easy Homemade Invisible Ink With Basic Household Items.

Do you work for the FBI and need to send secret messages about enemy locations? Do you want to tell your friend in class to meet up after class without he teacher noticing? Do you just want to do something cool and show off? In any case, this invisible ink will fulfil your goals - for no money or effort.

Materials:

1. Paper
2. Lemon
3. cotton bud or anything which can be used to write, e.g. your finger.
4. Something warm (a heater, a cup of tea, a warm bulb, whatever)

Dip your cotton bud into a lemon, making sure it is full of lemon.

Write any message you want (for example, the coordinates of your target, a secret password or a cypher). It will be invisible, so it can be hard to write accurately.

So, your partner in crime has sent you a secret message in lemon ink. trouble is, you can't read it. But how lucky you are, next to you, you have any warm object (in this case a mug of tea) and all you need to do is put the paper against it!

The message has appeared! and it says... hello... I wonder what that's a code for...