Invisible Ink

Invisible ink is also known as security ink or sympathetic ink. It is used for writing,which is invisible. Invisible ink is one form of steganography. The first record of it comes from Pliny the Elder in the first century AD.

How to Make Invisible Ink

Step 1 - Mix. Mix ¼ cup baking soda and ¼ cup water.

Step 2 - Wet your brush. Dip a cotton swab, toothpick or paintbrush into the mixture.

Step 3 - Write your message. Write a message on a white piece of paper and allow it to dry.

Step 4 - Apply the decoding stain. ...

Step 5 - Reveal the message!

 Invisible ink is heat activated.the acids in the liquid turn a different color and the message becomes visible. 

Uses of invisible ink 

Many uses may include anticounterfeiting good, property marking, hand stamping for readmission, children's games, and marking for the purpose.