April 29, 2008 4:00 AM PDT

New way to save energy: Disappearing ink

Posted by Michael Kanellos

Think of it as the future of today's paper.

The Palo Alto Research Center (PARC) and parent company Xerox are experimenting with a type of paper and a complementary printer that would produce documents that fade away after 16 to 24 hours. A restaurant, for instance, could print its daily specials on a piece of paper, attach the pieces of paper to menus, and then collect the sheets of then-blank paper in the morning to run through the printer again.

How does it work? The paper is coated with photosensitive chemicals that turn dark when hit with UV light.

Users don't have to wait for the paper to fade either. By running it through the special printer made for this paper, the printer will erase the old image before putting the new one on.

The paper and printer could hit the market in a few years.

The same sheets of paper can be run through the printer hundreds of time, according to tests conducted by Xerox, said Eric Shrader, area manager, energy systems, device hardware laboratory at Xerox. Typically, the paper isn't reusable only when it gets damaged or crumpled.

The idea is to cut the amount of energy consumed in making paper and printing. Like refurbished PC makers have noted, reusing an item consumes a lot less power than making a new one, or even recycling one.

It takes about 204,000 joules to make a sheet of paper, Shrader said. That's about the same amount of power required to run a 60-watt light bulb for an hour, he added. Recycling that same sheet of paper takes about 114,000 joules.

Printing a conventional 8x11.5 sheet of paper takes about 2,000 joules, he said.

Reusable paper takes a lot less effort. It only takes 1,000 joules to print an image on one of Xerox's reusable sheets of paper, and that's if you use the printer to erase the image. If you let the image fade naturally, it only takes about 100 joules to print. It takes energy to produce the special paper, but the energy consumed in recycling fades out.

"Being able to reuse paper is a big energy win," Shrader said.

This piece of paper is blank, but about eight hours ago it said, 'Reusable Paper. Xerox Parc Inside Innovation at Xerox' in block purple letters.

(Credit: Michael Kanellos/CNET Networks)

Energy has become a major focus of research at PARC over the last three years. The lab, which Xerox opened in the '70s, helped create the PC, inkjet printing, and Ethernet networking. Xerox, however, didn't commercialize a lot of these inventions successfully; instead, companies like Apple borrowed liberally from the lab to great effect. PARC now functions relatively independently, coming up with inventions to license to others.

Not every document is right for reusable paper. Presentations and legal contracts probably need to be printed on something more permanent. But lunch menus, daily work summaries, and memos from meetings can all potentially take advantage of this. Xerox says that 44.5 percent of documents are printed for one-time use and 25 percent of all documents printed get recycled the same day. (Lyra Research estimates that 15.2 trillion pages get printed worldwide a year, a figure that will grow 30 percent over the next 10 years.)

"Think of the Google map you printed to get here," Shrader said. "Thirty years ago, we said the future was paperless."

The paper and the printer will be a little bit more expensive than their conventional counterparts. The photosensitive molecule embedded in the paper is proprietary.

While the paper shown in the photo is yellow with purple ink that appeared later, Xerox has produced white paper and can come up with a variety of ink colors. The company, however, has used yellow paper as an example so that focus groups know what sheets to reuse and which to recycle.