In the wizarding world, the aparecium spell can reveal invisible ink or hidden messages. Hermione tries to use it on Tom Riddle’s diary in The Chamber of Secrets. We are going to reveal a hidden message here, too, but we’ll use a chemical reaction instead of a magic charm. 

We’ll use lemon juice to write an invisible message and then we’ll use heat to drive the chemical reaction that will reveal it. Lemon juice dries colorless on paper when you write with it, so it can be used to leave an invisible message. Even though we can’t see them, there are many chemicals present in the lemon juice that are left on the paper. Some of those chemicals can go through a reaction called oxidation which causes them to turn brown. We can make that reaction happen faster by adding heat with the iron. 

Here’s what to do: 

  1. Gather your supplies
    1. Lemon or lemon juice
    2. Paper
    3. Q-tip or paint brush
    4. Iron (have a grown up help)
  2. Create your invisible ink by squeezing the juice from the lemon
  3. Use a Q-tip or paint brush to write a message with lemon juice on the paper and let it dry. The message should be invisible.
  4. Carefully (have a grown up help), set the iron on top of the invisible message. The heat from the iron will drive the chemical reaction and reveal your hidden message.
  5. After a few minutes, pass the iron over the paper.

Watch here: