A printing process based on reprintable papers has been developed that would help avoid wastage of paper. The new system envisages tiny dots of special ink encapsulated within an ordinary paper. By raising the temperature in the printer, the paper can be wiped clean which is stable in the same state at the room temperature. For reprinting, the ink can be turned black again by lowering the tempera ture. The paper can be used for reprinting several times, says Joseph Jacobson of the Media Laboratory at Massachusetts Institute of Technology, USA. For colour printing, three different-coloured inks are switched on and off using the light from three different coloured lasers. The ink can be mixed in each micro-bubble because each laser only activates its own ink. In monochrome, a single sheet can be reused 100 times in a printer with the running costs of a fax machine. In laser printers full 4,000-shade colour appears on each page that can be used for 1,000 times.