How Does Invisible Ink Work?
Purposes and Function An invisible ink is any kind of liquid ink that is invisible to the naked eye after it is used to write a message. It will remain invisible unless a person with knowledge of what ink was used applies the right developing agent to make it visible. For this reason, various types of invisible inks have applications in espionage and security. Heat-Activated Inks The most simple form of invisible ink is a heat activated. These types of inks are often improvised because they can be made from many kinds of organic liquid. They work because once dried and exposed to heat, acids within the liquid will oxidize (gain oxygen molecules) and gain color. An easy heat-activated ink can be made in your own kitchen to demonstrate this principle. Simply scratch out a message on paper using a quill pen (or just a toothpick) dipped in milk. After the milk has dried, hold the paper close to a high light bulb or burning candle. As the page heats up, the message will appear in brown lett
