Densities climbing/ color going haywire

Discussion in 'Komori Printing Presses' started by simon700, Feb 21, 2017.

  1. simon700

    simon700 Member

    Joined:
    Apr 2011
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    Location:
    NEPA, USA
    I've been running an L5-28 + coat (circa 2007 I think) for about 4 years. (former Harris, Heidelberg, MAN-Roland, Mitsu guy). When I first got to this shop, they were having all kinds of problems, as this was their first "big" press. (28" 'Big' ha-ha) Any way, we got all of the major problems sorted out, and life was good for a couple of years. This past month I've had all kinds of problems holding color. In the morning (press cold) I have to push a lot of ink. By mid day I am cutting ink and upping water. Always been, that's OK, but now when I am several hundred sheets into a run, the colors all climb (more so Cyan & Mag) and behave erratically. Nothing has been changed as far as my consumables (ink paper fount solution etc) Dumping fountain solution seemed to help a little. I can't think of anything that has changed. Chiller is working OK. Anyone have advice or clues?
     
  2. aqazi81

    aqazi81 Senior Member

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    KARACHI PAKISTAN
    Check your rollers condition, if they are glazed or you see calcium build up. Also check your copper rollers for any oxidization.
     
  3. mantman

    mantman Senior Member

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    Greece
    You could try taking off rollers for a good scrub to take off any residues of wash/calcium and set them again, how long are the rollers on the press perhaps its time to change them
     
  4. simon700

    simon700 Member

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    Location:
    NEPA, USA
    Update: I spoke with other pressman there today (4c GTO) and he has noticed the same issues, mostly on Mag he said. I checked fountain solution pH (unfortunately no conductivity meter) and it read 4.5. When everything was in its "Happy place" about a year and a half ago pH was 3.5. I know this because we changed plate manufacturers at that time and a tech came out and measured everything. I have his report. I also made a fresh batch and that tested 4.5 in the bucket. We use municipal tap water, and that may be the culprit, or maybe the fountain solution. I seem to remember opening a new 5gallon kit around a month ago. I spoke to solution rep today, he suggested calcium also, but that doesn't seem to fit. Problem is on all stocks, coated and uncoated and I have not seen anything on rollers. We usually only wash-up on Fridays, and problem is the same in the beginning of the week as at the end. I had calcium issues in other shops and this doesn't look like that.
     
  5. aqazi81

    aqazi81 Senior Member

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    3.5 is too low. 4.5 to 5.5 is what required.
    As you say you only wash up on weekends so your rollers may not be in good condition now. Remove the rollers from press, as mantman suggested and scrub. Check roller sizes and any cracks or swelling, replace if needed.
    Finally set the rollers precisely.
    In my opinion, conductivity is more relative these days then measuring pH because most of the fountain solutions these days are buffered.
    Hope this helps.
     
  6. sp102

    sp102 New Member

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    Location:
    NORTHEAST U.S.
    MAINTAIN SPEED make ready at speed you plan on running keep ratios around 130 both water and ink
     

  7. turbotom1052

    turbotom1052 Senior Member

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    Vermont
    modern fountain solutions are buffered to run within a very narrow ph window. Id suggest that you try mixing a batch with the minimum recommended dosage set by the fountain solution manufacturer. Then use a conductivity meter to measure conductivity to a starting point of about 800 to 1000 above the measurement of the untreated water from your source. For example.... your tap water measure 200. You mix solution to get it reading between 1000 to 1200. Before doing this I would create a log over the course of a week, taking multiple readings per day, to determine if the water from your tap is consistent. Very often this is NOT the case. I consider a conductivity meter a MUST in any modern pressroom. Ph is not a reliable pressroom measurement once you've established your proper mixing dosage, and even then it can be misleading. If your press is equipped with a doser then I would also verify that the doser settings are accurate.It should also be noted that your measurements should be done BEFORE adding any isopropyl or alcohol substitutes as alcohol subs tend to skew the readings.