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Gloss or Gas Ghosting

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  • Gloss or Gas Ghosting

    I know a printer who just took a big hit with this issue. A small patch of PMS 287 as well as bands of 287 screens ghosted on a black solid. Overprint varnish would not make the ghost less visible.

    In hind sight, the press operator could have suggested that the 287 print first and thoroughly dry before printing the black solid. Might have dodged the bullet there.

    What if...the job was run on a 6 color with aqueous coater. Does in-line aqueous coating make gloss/gas ghosting a thing of the past, or does it still happen when the planets are aligned for trouble?

    UV printers need not reply, no gas to ghost.

    John Lind
    Cranberry Township, Pa
    724-776-4718

  • #2
    Re: Gloss or Gas Ghosting

    Hi john,

    I have done a bit of digging on google and found that gas ghosting can still happen on aqueous coated work, but there is info which contradicts this. From what i can tell gas ghosting is caused by the solvents in the ink being trapped under the layer of ink (i assume between pigment and binder), if an aqueous varnish was on top of this it would still happen as the issue is with the solvents in the ink layer. But one quote suggests that this link was made as result of the ir and hot air speeding up the ink drying which evaporated the solvents quicker leaving less trapped gas to ghost. I was also told that gas ghosting would not happen with aqueous coating but it looks like it wont happen because the ink drys faster releasing more solvents not because of the coating. If you have an IR dryer then try it.. next time i get a job on which may ghost ill try it. PS wouldt an overprint varnish make the situation worse as now there is an extra layer of ink to get through.

    Hope this helps Paul

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    • #3
      Re: Gloss or Gas Ghosting

      Paul:
      The gas/gloss ghost had already happened, and the over print varnish was applied thinking it would make it less visible. In the early days of this problem, early GATF studies, this sometimes helped save the job.

      The ink company is scratching their head over this. It's not a predictable issue. It gets more crazy. According to the press operator, and my own eyes, you can't see the ghost until you apply the offline varnish or coating. The varnish won't wet or lay where the PMS287 has left drying "fumes".

      More details to follow as the truth is revealed.

      John Lind
      Cranberry Township, PA
      724-776-4718

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      • #4
        Re: Gloss or Gas Ghosting

        Hi John,

        Try you paper company too, i may be a the paper which is causing the localised gas ghosting.

        Best of luck.

        Paul

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        • #5
          Re: Gloss or Gas Ghosting

          We had a similar problem a few years ago. We ran the sheets back through and overall Aqueous coated. A nice thin coat.

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          • #6
            Re: Gloss or Gas Ghosting

            I also have had success with a post finish of a thin layer of Aqueous

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            • #7
              Re: Gloss or Gas Ghosting

              For the record, the printer tried aqueous coating and that would not wet the ghosted area of the PMS 287. The 287 was surrounded by solid black, and the ghost was in solid black. That job was never really fixed. Even after we put two additional coats of varnish, making it impossible to dry, ever, and impossible to fold or convert, I could still see the ghost. I was ready to jump off a bridge as we hand folded and converted the product and delivered it to the customer. Guess what they said? Nice job, it looks great.......Go figure. I guess my standards are too high. From the customer's perspective, they who expect nothing are not disappointed.

              John Lind
              Cranberry Township, PA
              724-776-4718

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              • #8
                From what I have done in the past was run one side and let it sit for awhile to get the solvents out. Try winding the paper once or twice while it sits. I had this problem a couple years back with a solid of 648 blue. Also try using a low VOC ink. But I know blues with alot of reflex in them tend to be a problem.

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                • #9
                  Pantone set standards way to dark for most inks using a lot of reflex. Whenever we run inks like 286,293 and so on we really have to pump the ink to get to density and I think this is why the dark blues are more prone to gas ghosting. We run a bunch of jobs for one customer that require 2738. We run this with full solids along with four color process and inline aqueous and have never had a problem with gas ghosting. Aqueous has an onion skin surface that allows the gas to escape through the aqueous where I dont think you can do this with varnish. We have an extended delivery that allows more time for the IR and the air knives to set the ink better which may explain our success. In the past I always thought the way to prevent the ghosting was to print one side, let it dry, varnish it then do the same with the other side.

                  The only way I can see where aqueous would help this it that it goes through the IR and the air knives to reopen the ink before the Aqueous hits it and brings the stack temp around 95 degrees F.

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                  • #10
                    We've been having this problem a lot more lately, and all the jobs were aqueous coated. However what we've found is they've all been printed 4cp/4cp on the same stock- 70# anthem gloss. It seems that the low voc 4cp inks we use set up and dry extremely quick, maybe too quick. It takes about 3 hours for the ghosting to appear. We usually see the ghosting in the black first, then the other colors hours later. The jobs were flipped and printed right away which set us up for problems. BUT, what's interesting is we've ALWAYS done things this way and NEVER had any issues. Same inks, same coating same everything but now somethings changed. If we print the same job on a different stock, no problems. Print the job on the same brand of stock just thicker basis weight- no problems.

                    We ended up switching stocks and that virtually eliminated the gas ghosting. If we have to run a job on a known problem stock we'll schedule in time for the job to be winded and sit (hard to do in today's environment). Also we switched to a higher micron spray powder from 24 to 32 and this helped. The chemical make up of the papers are changing, combined with the new generation of low voc ink vehicle and pigments seem to bringing this problem back around.

                    Mike

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