The Mossad Pen is an updated version of the classic disappearing ink. To make the ink disappear, heat the paper to a temperature above 140°F (60°C). Devices such as a blow dryer are a good option. To make the ink reappear, cool the paper to a temperature below 15°F (-9.4°C) such as putting the paper in the freezer. The ink can disappear and reappear as often as needed.
 
*This pen is only available in black ink and designed to work on white paper only.