Ultraviolet or UV ink can be handy for secret messages or hidden decorations. The ink only appears when an ultraviolet light source is shone on it. As soon as the UV light is turned off, the writing becomes invisible again. There are different ways to make UV ink, and you might even already own something in your house that can be used as UV ink. With a little creativity, you can have fun with UV ink in no time.
For making UV ink from cleaning items, you can use a washing powder specially designed to wash white clothes, or use petroleum jelly.
Use a toothpick, cotton swab or brush as a writing instrument to dip into the detergent or petroleum jelly, Draw or write something with your secret marker on a piece of paper.
Go into a room—one without windows is best—with the paper and a UV lamp, turn on the lamp and turn off the room lights. You should be able to see the secret writing or drawing on the paper.
Ask at your area craft stores for invisible UV powders. You might be able to choose from various colours, such as bluish white, bright red and green.
Mix the powder with the liquid in which it becomes soluble, which can be water, alcohol, acetone or toluene. You should follow the powder manufacturer's instructions for this step.
Go into a dark room and shine a UV light on the solution. The ink should glow. You can make the ink brighter by adding more UV powder and make it less bright by adding more liquid.
Use the ink to write on a piece of paper. It should be invisible under normal light and become fluorescent under UV light.
Saliva is naturally fluorescent, so you can use it as invisible ink if you don't have any other materials to use.
When mixing powdered UV ink, you should wear a crafting or home-repair safety mask and work in a well-ventilated area.