Invisible Ink with Onion Juice

Making invisible ink is a lot of fun, you can pretend you are a secret agent as you keep all your secret messages hidden from others. All you need is some basic household objects and the hidden power of onion juice. 

What you'll need:

    onion
    grater
    knife
    Bowl
    White paper
    Empty Refill
    Lamp or other light bulb or candle

 Instructions:

    Cut the onion into half and peel.
    Grate an onion with the help of grater.
    Squeeze the pulp in a bowl to get the juice.
    Dip the empty refill into the juice and write a message onto the white paper.
    Wait for the juice to dry so it becomes completely invisible.
    Can you read it ? No !
    When you are ready to read your secret message or show it to someone else, heat the paper by         holding it close to a light bulb or carefully hold the paper over a candle flame.
Now you can read the message !!!

What's happening?

Onion juice is an organic substance that oxidizes and turns brown when heated.  Onion Juice burns at lower temperature than paper.
Other substances which work in the same way include  Lemon Juice ,orange juice, honey, milk, vinegar and wine.
Invisible ink can also be made using chemical reactions .