PALO ALTO, Calif. - How many times have you printed out a document on a sheet of paper, used it once, and tossed it out? According to Xerox's Palo Alto Research Center (PARC), 44.5 percent of the time that's exactly the fate of a printed page. Print out something like directions or a memo for quick reference and then it's off to the recycling bin.

Paper is often used for all of a few minutes and tossed out. That's a waste of more than just the paper, but the power used to create it. It takes 204,000 joules of power to create a new sheet of paper and 114,000 joules to recycle one.

So what if you didn't have to make new pages but could reuse the old ones? To reduce that waste, PARC has among its many projects a reusable paper where the printout fades away after 24 hours, allowing it to be reused.

The demo was part of a number of technologies on display here at the vaunted Palo Alto Research Center which has historically produced numerous breakthroughs in computer graphics, user interface, networking and other technologies.

In the case of the erasable paper, Xerox partnered with Xerox Research Centre of Canada to create a paper that can be reused again and again, until it rips, that is. The concept, as Eric Shrader, area manager for PARC's hardware systems laboratory described it, is similar to photoreactive glasses that automatically darken when you go outdoors into the sun.

The paper itself is standard paper that can be recycled and will only cost around two or three times the normal price of paper –- or about two to three cents per page instead of a penny.

PARC developed compounds that change from colorless to colored when they absorb a certain wavelength of light, but then change back to colorless over a period of time. The light used to bring out the colors is ultraviolet light. So when the page is printed, instead of the page running over an ink drum, a light is simply shone upon it.

Paper that self-erases

Shrader estimates that the current resolution is around 150 dots per inch (dpi), not exactly comparable to the 300, 600 or even 1,200 dpi laser prints and photocopiers are capable of reaching. The paper self-erases in about 16-24 hours, faster if it's warm, slower if it's cold. It can be used as long as the paper holds out, which Xerox figures to be about a dozen times or so.

The result will be less paper needed and consumed, less toner needed, since no toner is required, and less power to print the page. But reusable paper is still a way off. Shrader couldn't give an estimated time of availability, as Xerox is still working on increasing the dpi and printing speed, among other things.