Invisible Ink Decoder

Invisible Ink Decoder

Any good spy will need to pass information securely from time to time, and sometimes this means using a bit of low tech magic. One way to do this is by writing messages in invisible ink, which is a pretty simple trick. In fact, kids can make their own invisible ink and decoder with ingredients found in the kitchen!

Many types of invisible ink require a special chemical reaction to reveal them. Some use heat, which darkens the paper more than it would without writing on it, to make a message visible. Others can be revealed by a chemical (such as an acid or base) that turns the paper a certain color.

One of the most common types of invisible ink is a heat activated substance, which can be written on a piece of paper and then exposed to an iron or a hot light bulb to reveal it. Other heat-activated invisible inks are made from organic liquids that oxidize (turn brown) when heated, such as lemon juice, apple juice, onion juice, milk, vinegar and more.

Some invisible inks also glow under a blacklight, which can be used to reveal messages hidden on a piece of paper. Laundry detergents contain a white whitening agent that glows under UV lights, so it’s easy to create a homemade invisible ink pen for this purpose. Kids can have fun writing and revealing secret messages, as well as using their invisible ink pens as a creative night light for their “secret missions” around the house.