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A simple method to erase printed toner from paper would allow the same sheet to be used over and over again before going to the recycling bin, easing the environmental burden of paper consumption.
The new unprinting technique is designed for coated glossy papers used for flyers, packaging and magazines. Its developers say they are are working on integrating the process into conventional home and office printers, hinting at future printers could have an unprint button to wipe paper clean for reuse.
Paper boasts the highest success rate among recyclable waste materials. Nearly two-thirds of paper and paperboard products in the U.S. are recycled annually. And the statistics improve even as overall paper use seems to be going down.
Recycled paper prevents trees from being chopped down, and it uses less energy and water than paper made from wood. But recycling paper to make pulp still uses a lot of energy and requires the use of harmful chemicals.
Others have previously come up with ways to make rewritable paper. The techniques involve specially formulated paper or the use of laser pulses to remove toner from standard printer paper. The laser process can damage the coatings on glossy paper.
So the Rutgers engineers swapped the laser with a xenon lamp. They expose coated paper to intense pulses from the lamp, which weakens the bond between the toner and paper. The toner can then be removed by dabbing gently with an ethanol wipe.
The method works best with black toner since it absorbs the light pulses the most. But the researchers could also erase blue, green and red print by first coating it with black toner.
“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,” said Rajiv Malhotra, a professor of mechanical and aerospace engineering at Rutgers University who led the work reported in the Journal of Cleaner Production. “By eliminating the steps involved in conventional recycling, our unprinting method could reduce energy costs, pollution and greenhouse gas emissions.”
Source: Michael Dexter et al. Intense Pulsed Light unprinting for reducing life-cycle stages in recycling of coated printing paper. Journal of Cleaner Production, 2019.