How to make invisible INK at home?

           

Ingredients: 

                         Just lemon juice.

     Write your message on a piece of paper with a brush or toot pick embedded in lemon juice. Let it dry completely.

    To read the message heat the paper for a while (for instance hold it close to a light bulb) until the words become visible. 

Warning: do not hold paper too close to the heat and be careful not to let it get too hot!

Chemical explanation: 

                  Lemon juice is a mild acid that weakens the paper upon contact.

So when you heat the paper the part with the juice burns before the rest 

making your message visible.