[afshin]

A special paper could be produced that, when something is written on it with special ink with a pen, it initially appears to be invisible, but after connection of 6.3 or 12.3 voltage electricity the words become visible. Special eye glasses could be made to make the invisible writings visible. The writings could also be made sensitive to infrared light.

Reward: One for my self

[swimmer]

a pen was invented 7 years ago . u use its first end two write with a transparent ink , and by using he second end which has a special light u can read what u wrote .

the transperent ink glows red when u direct the special light on it .