back to article Cambridge boffins build laser 'unprinter' to burn pages clean

A team of scientists from the University of Cambridge has published plans for a laser "unprinter", which vaporizes toner used in printing to leave a clean sheet of paper. The idea of reusing printed paper has been around for a while, and it's not too difficult provided you use expensive coated paper. Toshiba has recently been …


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  1. Nuke

    And the point is .........

    ...... what ?

    1. Anonymous Coward
      Anonymous Coward

      Re: And the point is .........

      There are loads of applications. Tax discs; transferable bonds; transaction records; name just what I've thought of in 5 seconds of evil plotting.

      Do they need anyone to test this wonderful new technology?

  2. Mage


    Re-use is more efficient than recycle.

    Now if we could go back to returnable bottles that are reused instead of crushing them...

    1. HeNe

      No, It's Not So Simple

      One must include all energy costs and all related pollution in order to correctly decide whether A is better (cheaper, more environment-friendly) than B.

      How much power does it take to "burn clean" a sheet of paper?

      How much pollution does vaporizing a sheet's worth of toner create? How toxic is the vaporized toner?

      And, why are we still grinding up trees and bleaching the pulp to make paper, when other plants provide more pulp per energy unit input?

      Why can I no longer buy lower-cost papers, such as "flimsy" and "pulpwood", which were available during up through the 1970s?

      (But, that's a separate topic...)

      1. Jan 0 Silver badge

        Re: No, It's Not So Simple

        You're right about the real costs, but that's people for you. Reusing is no bad as a rule of thumb.

        You can still buy 'flimsy'. Look for Bank Paper at c. 40 - 50 gsm (NOT Bank Note Paper!) E.g.

        You'll find pulpwood, and plenty of others, in art or craft suppliers. E.g. It starts getting dodgy for writing at about 25gsm!

        1. HeNe

          Retail Paper Prices vs Cost of Production

          Thanks for the sources, but ... trying to economize and be eco-friendly by using a "lower" grade of paper results in a SIGNIFICANTLY higher end-user cost, even though the "lower" grades of paper cost LESS to produce!

          (1 ream == 500 sheets)


          18.95 GBP/ream 3.92 x cost for 1 ream 20# copy paper


          S307-809 Pad 9"x12" 50 Rough, Tape (top), White

          34.00 GPB/ream 7.02 x cost for 1 ream 20# copy paper

          "copy paper"

          HP Copy A4 Paper - 80gsm - Box of 5 Reams (Pack of 5)

          4.84 GBP/ream

          1. TeeCee Gold badge

            Re: Retail Paper Prices vs Cost of Production

            Simple supply and demand economics.

            Back in the day of typewriters and handwriting, this sort of stuff could be used for less important work.

            These days just about everything is printed on computer and any printer with a feeder system tends to have a cow at the sight of underweight or rough paper. Thus it's not in demand, is a specialist order and costs more.

            Our DE offices have moved internally to only using unbleached, recycled paper to wave their "greenness" credentials. That goes through OK. No idea whether it's cheaper, but it is worse than bloody useless when printing something on a B&W laser that has colour in the original. It's also worse than worse than bloody useless in a colour printer.......

            1. Eric Olson

              Re: Retail Paper Prices vs Cost of Production

              Is there any legitimate reason these days to print anything out that isn't meant for archival or storage? Even businesses are catching up to the concept of paperless, though usually that's more to do with limiting liability (very difficult to subpoena old emails that were never printed and have a 36 month deletion policy when you called all your clients muppets and described the toxic products you were selling them) and making sure there are no traces of poorly thought-out business plans or processes (under the disguise of ISO 9001 compliance).

              This laser could make things less lucrative for companies like Iron Mountain. Along with their archiving business, they seem to throw in on-site shred bins that really just provide them with tons of paper they can pulp and sell to the highest bidder for recycling. Clearly this must be profitable, as their clients seem to be encouraged to tell their employees that even personal records and other destructibles can be brought from home to ensure identity security.

              1. multipharious

                Re: Retail Paper Prices vs Cost of Production

                Check how much those bins and proper onsite (read in a truck outside your company) destruction service costs. It might be profitable for the shredding companies to sell the shredded paper, but I looked into the secure bins and they aren't free.

                As far as using a deletion policy to protect an organization? It only increases risk. Risk that you don't have an original copy of the email or file, stored in a documented manner that will make the judge satisfied that sufficient care was taken to avoid tampering. And that your organization is at least trying half-heartedly to achieve regulatory compliance. Otherwise when the plaintiff brings their complaint before the court and presents the evidence (which could be fraudulent,) the burden of evidence shifts to the defense.

                At that point, the judge has a number of options available to him/her if your company doesn't settle outright. Those options include ordering forensic examination of hard drives, electronic discovery for prohibited things like PSTs, disclosure of backup tapes, etc.. Deleting a primary copy only increases the chances that it exists somewhere outside your control.

  3. Stratman

    I can see a whole new series of plotlines for CSI in the offing. Of course each zapper will leave its own unique signature etc. etc.

    1. Notas Badoff

      When new news is old news is newly used news

      "Your honor, laboratory tests proves the paper these financial reports were printed on is at least 15 years old. They are genuine and there was no conspiracy to defraud. It is all here in black and white!"

      "What about the toner? Has anybody dated the toner?"

      "Is that possible?"

      "The paper could be recycled!"

      "The toner could be recycled!"

      "This plot might be recycled!"

      "It's Hollywood, it was!"

  4. CABVolunteer

    Patent it OR commercialise?

    ".... considering whether to file patents or commercialize the technology"

    Why not do both? In fact there doesn't seem a lot of point in paying the patent application fees unless there's going to be commercial exploitation.

    1. JetSetJim

      Re: Patent it OR commercialise?

      The problem with a patent, now, is that any old mucker can sell a 532nm laser pulsing at 4ns at a target detected with a vision sensor. They've published so the whole thing is in the public domain. Stuff some edge/residue detection algorithms in there and you've got pretty much the complete package - what's left to package?

      Perhaps they've invented something cunning to deal with the fact that most discarded paper is rumpled into a ball...

    2. g e

      Re: Patent it OR commercialise?

      Yeah. Patent it before Johnny Foreigner does (or perhaps Hank/Chuck/Earl Foreigner) and bends you over for infringement.

      Just DO IT.

  5. Irongut

    I wonder how well it removes the print and if any traces are left behind. If it's good enough maybe it could replace the office shredder.

    1. multipharious

      good question

      I would guess it would leave a negative oxidization image at a minimum (i.e. yellowing around comparably whiter letters where the ink was.) It could also just bleach the ink and leave an "invisible" residue that could be seen under a certain spectrum of light. Either could be enhanced.

  6. Anonymous Coward
    Anonymous Coward

    Already invented

    You just need to use the same ink that petrol receipts are printed with. That seems to disappear completely before the end of an accounting period and you're left with a shoe box full of blank receipts for the VAT man.

    1. John McCallum

      Re: Already invented

      You need to ask for a VAT receipt till roll type ones usualy say that they are not VAT receipts

      1. John Brown (no body) Silver badge

        Re: Already invented

        Yeah, you ask for a VAT receipt and it come out of the same till printer.

    2. TeeCee Gold badge

      Re: Already invented

      This excuse (c) everyone with a tax return to fill in and a handy supply of blank till rolls.

  7. Cameron Colley

    But why?

    I was under the impression that paper nowadays is only used for archive or scrawling all over in meetings, and that is apparently being replaced by tablets, do some people really still print everything out then throw it away?

  8. Anonymous Coward
    Anonymous Coward

    Doesn't this leave a risk that someone will erase part/all of a signed document and replace it with something else?

    They should also patent some inks that are immune to their process :-)

    1. Anonymous Coward
      Anonymous Coward


      Don't let Goldman Sachs know about this!

    2. Charles 9

      Interesting points, indeed. The old "bleached document" trick taken to another level. I suspect the way the laser works will leave traces (since they DO mention the fact that it CAN be overused). So it's probably not going to be practical for the "will switcheroo" but in terms of common document confidentiality it could save some use of the shredder service. Blank the "just secret" documents and reuse them so that casual inspection can't determine what it was. After a few runs, THEN send them to the shredder.

    3. Anonymous Coward
      Anonymous Coward

      if there is more than one copy printed at the same time then it will be for forensics to decide whats been changed, considering most (all) lasers leave a signature on the printed document then surely any changes will be easily detected especially as the deleting can affect the paper

    4. James Micallef Silver badge

      Right on!

      Imagine all the fun criminal types would have if they could erase all of a document except for an (authentic) signature, and then print whatever text (instructions to bank, change of will.....) they want around the signature.

  9. Dig

    too late

    but apple patented this in 2015

  10. Anonymous Coward

    Go on then

    siht tnirpnu

    1. TeeCee Gold badge

      Re: Go on then

      siht tnirpnu

  11. dssf

    Sort of like "tatoo remover" but for paper...

    I wonder if this is an adjunct that sprang from the loins of a defunct DARPA project, wherein spies coming in out of the cold could release messages or identity authenticators ... wait.... lase-erase that thought...

  12. mhoulden

    All very well...

    ...but can they invent a device that removes coffee stains and animal footprints from paper?

  13. Muckminded

    Does it work on forum posts?

    The ethereal is more real now than real. Supposedly.

  14. mfritz0

    Would this work on currencies? There needs to be a way to treat paper so this won't work on money.

    1. auburnman

      Why? The worst you could do is destroy money, and you can do that without a custom laser. I suppose theoretically a rich person could invalidate some real banknotes in a way that they would pass casual inspections but not be accepted by a bank, maybe to 'poison' the money supply of a person or business. But then I think we're straying into CSI plot territory again...

    2. David Knapman

      I've got some bad news for you

      If the "currency" you have was printed by a laser printer and normal toner...

    3. PT

      Recycling currency

      Not by this technique presumably, but US one-dollar bills can be (and have been) bleached and overprinted with higher denominations. The results don't stand up to examination by eye, but they're good enough to deceive some electronic bill validators that rely on the optical characteristics of the paper to establish genuine-ness and only read the denomination from the print.

      1. Charles 9

        Re: Recycling currency

        Most Treasury-approved bill acceptors have a few more smarts in them. They'll use the basic optical test only to check for singles. For fives and up, they'll start looking for harder-to-casually-fake things like the fluorescent security strips which are in different locations for each bill (and singles don't have any). The acceptors used in points of sale (or other first-line areas where currency is handled before being routed to banks) are made to higher standards, have more detectors to check for things like bleaching, and can generally sniff out any fake short of a supernote.

  15. Blunderbuss
    Thumb Up

    Decide wheter to patent or not?

    "They have found some papers hardier than others, and are continuing experiments while considering whether to file patents or commercialize the technology"

    Wow, how nice to see people giving consideration as to wheter a patent is worthwhile or not rather than just filing for the patent automatically as well as patenting everything else that is vaguely associated with it.

  16. Bill9

    Laser 'Unprinter'?!?!

    Laser Eraser surely....

  17. Shagbag

    Reusable Shit Rag?

    Maybe the technology could be extended to 'recyling' shit rag (toilet paper).

    Just keep that laser away from your arse.

    1. Audrey S. Thackeray

      Re: Reusable Shit Rag?

      "Just keep that laser away from your arse."

      If there was a laser that could burn shit off paper without damaging the paper then why not just use it to zap the clag nuts etc direct at source?

  18. Anonymous Coward
    Anonymous Coward

    Unnecessarily complicated

    Wouldn't it be quicker, easier and cheaper just to burn the whole book?

    (If that's what you want).

  19. thedweeb

    To make it even simpler

    Why don't they just develop a white toner? Then you could overprint the entire page in black, then print again in white, then print the whole page in white, then print in black, etc., etc. Eventually the sheet would be more like a cube with all that toner, of course, and become too heavy to lift. Is this a silly idea? Any sillier than theirs?

  20. chrubb

    all very good...

    but where are the sharks?

  21. tempemeaty


    Considering whether to file patents or commercialize the technology? WHAT!?



    Why? Richo, Minolta, Xerox, HP, Canon...should I go on? ANY printer and copier manufacture would want as the next feature in their next gen product just to say they have a new feature!

  22. Jon Green

    And the word of the day is...


  23. Anonymous Coward
    Anonymous Coward

    For some reason..

    I have a vision of the human race making things for millennia, then slowly but surely doing an about turn and unmaking it all. Not destroying it, just unmaking it. The apocalypse will not be some plague or nuclear disaster; just some loony getting a bit trigger happy with an unprinter and its various descendent un-* devices.

  24. Jon Brindley


    "The Cambridge team figures it has cracked the problem, and its unprinter can work with any laser printed or photocopied paper, with no need for special toner that's more expensive gram-for-gram than cocaine."

    Ah, journalists .. making analogies with things they really know about.

  25. 4HiMarks

    This sounds very much

    like a solution without a problem.

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