How is invisible ink used?
Invisible ink is applied to a surface with an instrument such as a stamp, stylus, pen, or even a toothpick. Soon after the ink is applied, the surface should return to its prior state. To make the ink visible again you can use one of several methods, depending on the type of ink used. There are primarily three methods: ultraviolet light, heat, and chemical appropriate to the ink type used. Toy invisible ink pens typically have two tips: one for invisible ink writing, and the other for making the ink visible again. Also common are play books which include a special decoder pen that children can use to reveal messages hidden throughout the material.
