Invisible Ink

Things Needed:
  1. Half a lemon
  2. Water
  3. Spoon
  4. Small Bowl
  5. Cotton Bud
  6. White paper
  7. Lamp or light bulb
  1. Squeeze the lemon juice into the bowl and add a 2-3 drops of water.
  2. Dip one end of the cotton bud in the juice and allow it to soak.
  3. Write something on the white paper, using the cotton bud and the lemon juice.
  4. Allow the paper to dry.
  5. To read the message, hold the paper close to a light bulb or a lamp. Make sure to take the help of an adult while attempting to reveal the message.
How does it work?
When the paper containing the message is exposed to a source of heat, the words written using the lemon juice become visible and appear brown.
Lemon juice is an organic substance that oxidises and turns brown when heated. When the message is written using lemon juice, the carbon compounds in the juice get absorbed by the paper’s fibres. The heat from the lamp/light causes the chemical bonds to break down in the dried lemon juice. When carbon comes into contact with air, it oxidises and turns brownish.