Laser de-printer lifts ink from paper, leaving it ready to be reused

An experimental printer documented by Cambridge University scientists in a paywalled Royal Society paper is capable of laser-ablating the toner off of sheets of previously printed paper, leaving them ready to be reused. The device uses picosecond pulses of a green laser that passes through the cellulose in the paper, but vaporizes the toner.

The primary goal of unprinting is to cut down on the carbon footprint of the paper and printing industries. Manufacturing paper is incredibly messy business that produces millions of tons of CO2 every year. Recycling paper is definitely a step in the right direction, but it’s still a very resource-intensive process. If we could simply delete sheets of paper, rather than re-pulping them, we could cut down on electricity usage, CO2 output, and most importantly fresh water, which is growing more scarce by the year. It would also be rather handy if you never had to buy another ream of paper, too.

In a worst-case scenario, The University of Cambridge unprinting method has half the carbon emissions of recycling; best-case, unprinting is almost 20 times as efficient. It’s now a matter of building the technology into a commercial device, which the team admits is probably a long way off. High-powered picosecond lasers are the reserve of labs… for now!

The laser unprinter (via /.)



  1. Handy for forgery. Get someone to sign to one thing, erase what they agreed to, print something else, preserving the signature.  If it’s done right, there’s no evidence of the document being a palimpsest.

    1.  Or you could just copy over the signatures – not that much more effort.

      Ideally both parties should have a copy of the contract – and there should be witnesses if it’s anything important.

  2. In Japan their thermal printing on reusable polymer paper is looking pretty good. No toner or ink at all, good print quality (I guess we could call it “burn” instead of “print”), one machine erases and prints anew, and as an extra incentive for internal office use, the paper is not out of reach, but it is far more expensive per sheet than paper. 

    IMHO it will be awhile before people give enough consideration to a sheet of paper to consider reuse if it is any additional step at all. The Japanese technology seems to nix that problem. 

    Mind you, this sort of thin would only be effective internally at an office or lab or class setting, until the tech is widespread.

    I think the cost of the thermal printers are already down to 4 figures, can’t remember the polymer paper cost. 

  3. “Picosec laser burns ink into clouds of carbon dioxide gas!”

    Better do it within a vacuum chamber, then condense the carbon vapor back into  …into  …toner-sized carbon particles!!!

    Even better, use it to fabricate industrial diamonds, buckyball crystals, or perhaps that incredibly expensive liquid:  inkjet printer ink.   No longer will you have to buy Baseblocks or leave your downtown apartment to hunt down trash for your Godti(tm) maker.

  4. Traditional Paper Production

    Grow trees (trapping carbon), make paper (modern mills generate all their power requirements from waste wood, so is just putting a proportion of the CO2 trapped back into the atmosphere), transport paper to users (this does use energy from non-renewables).


    Gather waste paper (energy from non-renewables), process into new paper (more energy from non-renewables), transport paper to users (even more energy from non-renewables)

    This laser technique

    Burn of toner (energy from renewables). Reuse paper.

    Which is actually the best for taking CO2 from the atmosphere?

      1.  Or turn used paper into MDF and make furniture (and grow new trees-goes without saying).

        And use more wood for construction generally (and grow more trees!)

    1. A wee bit over simplified.

      A) Growing trees isn’t some fanciful activity involving children sewing seeds, it’s an industrial process in itself.  Not to mention the practice of deforesting habitats to grow more efficient trees to be used for paper production; or the process of felling the trees before they hit the paper mill.  I’d also be incredibly surprised if the trees being planted would in any way offset the carbon output of the the entire paper making/distribution process.  Reforestation is a good way to negate the CO2 impact of removing trees from that area, but only if you leave them there.

      B) Recycling paper is as much about waste management as it is about saving trees, “About 35% of municipal solid waste (before recycling) by weight is paper and paper products.”.  Also, “recycling 1 ton of printing or copier paper saves slightly more than 2 tons of wood.” and “It has been estimated that recycling half the world’s paper would avoid
      the harvesting of 20 million acres (81,000 km²) of forestland”. and “The EIA claims a 40% reduction in energy when paper is recycled versus paper made with unrecycled pulp, while the Bureau of International Recycling (BIR) claims a 64% reduction.”

      Reduce > Reuse > Recycle > Throw it away and start again.

  5. The shredder industry is quite displeased with this development and will let you know all the reasons not to do it as soon as they can find some. (First step: take notes from the comments above.)

    1. Sure, the second and third hand paper industry will be huge. And it will employ people to iron the dog ears out and maybe discover a way to clean the chocolate from library books.

      On the other hand, maybe an office or school system of recycling internal documents would be a good idea.

  6. So this could eventually be built into the paper path of a laser printer?   Nice.  You just load the paper tray up with old printouts, and de-print away. 

    Hopefully it doesn’t work on gel pens, but I suspect those dye the fiber rather than melt toner onto it, and this technique wouldn’t work.

    1.  In my line of work (TV production), this would be great.  For each episode of my current show, we generate about 6 production drafts of the script (not counting earlier writer’s drafts which have a much smaller distribution), with an average length of 60 pages.  And we generally print out about a hundred copies, each of which is useful for a few days at most, and then gets recycled.

      We’ve made great strides in the last few years toward reducing our paper usage (distributing PDF files to most people, who, like me, don’t need a hard copy to scribble upon; and also printing on both sides of the paper which is a surprisingly rare practice in Hollywood when it comes to scripts, for a few reasons), but being able to instantly recycle our paper when we print out the next draft would be really cool.  Between scripts and contracts and schedules and budgets, our paperwork output is sinful.

  7. My money is on e-paper before this scheme. You don’t have to create big piles of printed paper and then “un-print” it. I’ve read thousands of pages worth of books on my Nook Simple Touch and no trees have been harmed in the process. Whatever happened to the clipboard-sized e-paper reader someone was showing off not long ago, anyway?

  8. This is great and all, but I suspect there’s a very great deal that can be done just in cultural terms to eliminate vast reams of printouts made for stunningly fucking idiotic reasons.

    1. I would actually worry that this would increase printing; which is likely a more damaging practice than the paper production itself (i.e. printer manufacture, ink, waste, energy etc.).

      On the plus side all that junk mail I get would be free paper!

  9. I’m curious if the “deprinted” page can be scanned and the original text revealed through some chemical signature.  If that’s the case, you’d have to be very careful what you deprint so not to have any confidential information out there…

    1. I wondered this.

      It’s a great idea either way, but it must leave something behind.  This would reduce uptake, depending on how difficult it was to ‘recover’ the original.

  10. Makes me want to do an art project with a scrolling feed (Twitter/Facebook/NYSE) Printed with a Laser Printer at the bottom and unprinted at the top with a Laser Unprinter, on one single loop of paper maybe 12 feet long would be neat to see that in some gallery. 

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