Invisible Ink

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You will need:

• A little fresh lemon juice. It needs to be squeezed fresh, but you only need a couple of teaspoonfuls.
• A cotton bud
• Some white paper
• A table lamp, ideally with an old style incandescent bulb, because you need to produce heat*. 

Here's what you do

• Dip the cotton bud in lemon juice and use it to write something on the paper. Your name, for example.
• Use just a little lemon juice at a time so that you don't soak the paper.
• Then let it dry completely. The writing should be completely invisible.
• Now turn the table lamp on. 
• Carefully, hold the paper near the lamp so that it warms up with the heat of the bulb.

What do you see?

You should be able to see the writing re-appear, in a brownish colour!

*If you don't have a table lamp that produces enough heat, you may have to get the help of an adult. With their help, heat the paper by running a warm clothes iron over it. This will also achieve the same result. In order to avoid creating stains, place a second piece of paper over the writing and run the iron over that one.