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Green Laser Erases Print

Quick bursts of green laser light can erase print, without damaging or discoloring the paper. Karen Hopkin reports

Every year, about 10 million tons of paper winds up in American landfills and incinerators, which is not only wasteful but adds CO2 to the atmosphere. Recycling helps, but even that material has to be repulped and paper-ized before you can use it to print out that recipe you’ll never make. But what if you could wipe the page clean and use it again?

Light amplification by stimulated emission of radiation to the rescue. A new study shows that laser light can erase the toner from a piece of printed paper. The approach appears in the Proceedings of the Royal Society A. [David Ricardo Leal-Ayala et al., "Toner-print removal from paper by long and ultrashort pulsed lasers"]

Taking a page from the art-restoration handbook, scientists sampled a variety of light sources to see if any could be used to strip the ink from laser-printed documents without damaging or discoloring the paper. UV and infrared were too harsh. But a bright green laser applied in 4 nanosecond pulses vaporizes the print, leaving paper that looks as good as new.

Such unprinters will probably run about 30,000 bucks, so they probably won’t catch on for home use. But people in the recycling world might find that the green laser fits the bill—for making paper that’s really green.

—Karen Hopkin

[The above text is a transcript of this podcast.]
 

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