Printed matter is literally disappearing at Palo Alto Research Center, Inc. (PARC). In partnership with Xerox Research Centre of Canada since early 2004, PARC scientists have been developing "erasable paper," temporary documents that self-erase within a matter of hours.

Although the computer interface has become more ubiquitous in daily activities, researchers at PARC discovered that "for some reason people still like paper," Eric Shrader, PARC area manager and project lead, said. Shrader is a mechanical engineer who has developed other products such as electronic paper -- a low-cost display medium -- and cost-saving printing technologies for circuit boards and solar cells.

Stemming from PARC's focus on corporate ethnography, Shrader discovered, from self-reports and from sifting through recycle bins, the types of documents that office workers print and then throw away or recycle on the same day. Such documents included daily calendars, e-mails and reference materials relevant for a limited period of time.

"I think the biggest 'aha' moment was at the very beginning, when we realized that so much of what people print is only temporary."

On average, people in offices print approximately 1,200 pages per month, of which 25 percent is discarded on the same day.

"I wouldn't want to be in the business of selling file cabinets any more. People are thinking about the archive as something that the computer people keep and not that the filing people keep," Shrader said.

Erasable paper, also known as a transient document, is exactly like regular printer paper but coated with a molecule that changes color when exposed to light. Shrader compared it to photochromic glasses, which darken in tint when people go outside.

The printer, now being developed solely as an attachment to standard printers, prints by exposing the paper to a UVB light source. Researchers are also conceptually developing a pen that writes on the erasable paper by using an internal light source.

Images remain on the erasable paper for a solid eight hours before gradually disappearing, but Shrader notes that they are still refining that part of the project. Initial feedback indicates that people would prefer the image to last longer, or to last until an undetermined point at which they no longer need the document. But Shrader wants to avoid options or variation in how long the image lasts because it would require people to make more conscious choices about printing.

Running the paper through the printer will also erase the current image, as heat is applied in the printer, which stimulates the erasing process.

To distinguish the erasable paper from regular printer paper, and also to identify it for reuse, researchers have given it a yellow tint. The reusable life of the paper depends on its treatment, but is potentially limitless. The paper is robust and does not need to be treated or stored differently than regular paper.

"You can reuse it as long as you can keep from stapling or crumpling it," Shrader said. In their own experiments, PARC researchers have reused a single sheet of paper between 50 and 100 times. "Most people think they'll wreck it after 20 times."

The simple concept behind the printer eliminates the need for ink and toner in printers, which contribute significantly to the cost of printing. Shrader anticipates the printer attachment will add only approximately 10 to 20 percent to the cost of regular printers.

And although the projected cost of the erasable paper is greater than regular paper, in the long term Shrader expects people to save money because of its reusability.

Beyond financial savings, Shrader predicts that the biggest impact will be the benefit to the environment. Aside from the reusability of the paper, the inkless and tonerless printers eliminate the waste generated from regular printers. In addition, fewer materials are needed, which thus reduces the amount of carbon emissions generated from transportation.

"From a life-cycle, carbon-credit analysis, we're saving on a bunch of different fronts," Shrader said.

However, erasable paper -- currently in prototype phase -- won't be out on the market for a while, he added.