Environment

New "unprinting" process removes text from glossy paper

New "unprinting" process remov...
The process allows one sheet of paper to be printed upon and then unprinted up to five times
The process allows one sheet of paper to be printed upon and then unprinted up to five times
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The process allows one sheet of paper to be printed upon and then unprinted up to five times
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The process allows one sheet of paper to be printed upon and then unprinted up to five times
A diagram of the unprinting process
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A diagram of the unprinting process

Although eco-minded people do send their discarded paper off to be recycled, the recycling process isn't entirely environmentally-friendly – it generally requires a lot of power, and incorporates toxic chemicals. Now, however, scientists have developed a new method of simply removing the printed text from sheets of paper, so they can be reused.

First of all, we have already seen systems in which lasers are used to remove printer toner from standard copy paper. Unfortunately, though, those lasers damage the polymer coatings found on the fancier, glossier paper used for packaging, advertising and many other applications. As a result, such paper is rendered unfit for reuse.

Scientists from Rutgers University and Oregon State University recently set out to address that limitation, replacing the lasers with a xenon lamp.

Located 1.5 inches (38 mm) from the surface of semi-gloss paper upon which black toner had been printed, that lamp emitted flashes of broad-spectrum Intense Pulsed Light (IPL). These weakened the paper-toner bond, without adversely affecting the paper's coating. When an environmentally-friendly ethanol wipe was then gently drawn across the paper's surface, all of the toner came off, leaving a blank sheet of paper behind.

A diagram of the unprinting process
A diagram of the unprinting process

The process doesn't entirely remove untreated red, green or blue toner, as none of them absorb the IPL as thoroughly as the black. They can be completely removed, however, if they're first printed over with black toner.

It is hoped that once developed further, the technology could be incorporated into commercially-available home and office printers.

"Our method makes it possible to unprint and then reprint on the same paper at least five times, which is typically as many times paper can be reused with conventional recycling," says Rutgers Asst. Prof. Rajiv Malhotra, co-author of a paper on the study. "By eliminating the steps involved in conventional recycling, our unprinting method could reduce energy costs, pollution and greenhouse gas emissions."

The paper was recently published in the Journal of Cleaner Production.

Source: Rutgers University

5 comments
paul314
So how much energy and ethanol and other consumables does the system use to unprint paper?
Rusty Harris
I've been in the photocopier business, since 1981. These "erasing" machines and what not have come and gone, but have not "caught on" because they are too limited as to what they do. One of the latest, a few years back was a Toshiba, that used a "blueish" colored powder toner. It printed on just plain paper, then, if you wanted to erase it, you put it into a separate machine. How it worked was pretty simple. To print, the fuser (which uses a combination of heat & pressure to melt the toner powder into the fibers of the paper) heated the toner at a lower level, than most machines. Then, to erase, you feed the paper into the eraser machine which used a HIGHER temperature, which would turn the resin color clear. If you held the paper to the light at the correct angle, you could make out some of the letters, although, not enough to gainfully read it. Then, the paper could be used up to 5 times. The problem is with each use, it will build up successive layers of toner, which means the next time you use it, the toner may not transfer from the drum, to the paper properly, because of the buildup of the older toner. The other problem was the specialty toner was WAY expensive! There have been other attempt to "green" the photocopier & printer machines, but, all have failed. Plus, in a competitive business climate, most businesses will shred their paper, for security purposes.
Funkytone
Show me a printer that uses Red, Green, and Blue toner?
highlandboy
Hmmm, at the cost of toner, printing a layer of black to remove colour sounds like a very expensive option. The cost of toner reflects the high cost of materials and energy to make it. No figures provided, but it sounds as if it may be better environmentally and visually to plant a few more trees.
MD
Funkytone.. ha ha.. CMYK all the way.