Everyone has done it: printed out a page or two of a report or e-mail to read in hard copy instead of on the computer, and then (one hopes) slipped it into the recycling bin. Xerox, which first commercialized the photocopier and a longtime supporter of the approximately 2.5 trillion pages found on desks and in cabinets, estimates that as many as two of every five printed pages are read just once and then discarded. That’s a lot of waste, and recycling is no panacea. It takes 114,000 joules of energy to recycle a single sheet of paper (202,000 joules to manufacture one virgin sheet), which is enough to power a 60-watt light bulb for almost 32 minutes.
But what if paper could be reused by erasing the image or text and replacing it with something else? Xerox Research Centre of Canada, based in Mississauga, Ont., has invented what it calls erasable paper. It’s still in development, after potential customers suggested a few improvements to the prototype—as well as some alternative uses, which Xerox is keeping under its hat—so there’s no telling when your supply cabinet might get stocked. But it will probably happen before we ever get used to reading everything digitally.
Here’s how it works:
1. Regular Xerox 4200 stock paper is coated with photochrome chemical compounds that darken in ultraviolet light. Although the photochrome molecules could be tweaked to turn nearly any colour, researchers selected purple to approximate the appeal of writing in blue pen. The paper is a faint yellow to differentiate it from non-reusable stock.
2. The paper is run through a standard multifunction copier equipped with a special LED light bar that digitally scribes the paper with UV light. The paper’s image fades at room temperature over the course of 24 hours, but can be erased instantly if run past the more intense heat of a copier’s fuser. The paper can be reused indefinitely, or at least until a sheet gets too wrinkled or torn. Researchers have cycled a page through 100 times with little change in quality.
3. Because the paper reacts to UV light, exposing it to daylight will gradually turn the entire page a faint purple. But re-imaging every pixel on Xerox erasable paper takes only about 200 joules.
