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Back to pressroom basics

Sep 1, 2005 12:00 AM


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Pressroom

Does this sound familiar? Your press was delivered, the installer and demonstrator did their jobs, the iron looked pristine, yielded excellent print quality and generally delivered as promised. A few months later, however, print quality and press performance mysteriously deteriorated, even though you didn’t change a thing.

Keep those rollers clean
In many cases, maintenance issues are to blame. Consider the press rollers. Improper roller maintenance can result in streaking, roller stripping, poor color control, picture framing, ink feedback to the metering rolls, plate blinding and hickies.

To control these problems, follow this procedure:

  • Remove the ink with a good quality blanket and roller wash.
  • Next, use a water rinse to remove the surfactants that many of today’s washes—especially the water miscible types—contain. (Don’t skimp on the water: Too little can result in stripping, poor color control, plate blinding and picture framing.)
  • Finally, examine the rollers for evidence of glazing. Glaze, which results in shiny rollers, can be solvent- or water-soluble. There might even be layers of each on the rollers. Some products remove only solvent-soluble glazes, while others work on the water-soluble types. Ask your pressroom consumables supplier for product suggestions and on-site demonstrations.
Calcium (a whiteish haze) is another contaminant commonly found on rollers. Calcium build-up can cause many print problems, including poor color control. Although diluted acetic acid and repeated water rinses will remove calcium, some specialty products are more efficient and ensure neither the fountain solution or ink train are contaminated after the rinse.

Is your fountain solution OK?
Don’t forget to optimize your fountain solution. Evaluate the fountain solution chiller/recirculator. A clean, well-maintained fountain solution reservoir is essential to maintaining ink/water balance and printing consistency. In addition to calcium, other contaminants can include paper, ink, solvent/wash and spray powder. Restoring optimum performance doesn’t end with cleaning the tank. Filters in the system should be changed once a week. Finally, ensure that the fountain solution is mixed according to your supplier’s recommendations. If you use a blending unit for mixing fountain concentrates with water, routinely check to see if the unit’s output is correct.

In your day-to-day operations, you should monitor and record both pH and conductivity on a regular basis. If the pH rises more than 0.5 units, or if conductivity increases more than 1000 microsiemens from your freshly mixed fountain solution, consider changing it regardless of age. Unless you have a treatment device such as FloClear (see box), it’s a good idea to change the fountain solution at least once a week.

Although pressroom technology has changed, the basics haven’t—it’s still ink/water balance and putting color on substrates.



An easy solution for hybrid & conventional jobs
FloClear, a GATF-award winning fountain solution cleaning system, reportedly reduces waste and time spent troubleshooting presses. Using a combination of filtration, separation and absorption technology to trap contaminants, FloClear cleans and restores the fountain solution used in web and sheetfed press dampening systems to what is said to be a fresh-mixed condition. Adopters report extending the usable life of their fountain solution for six months or more; not needing to change fountain solution when switching among hybrid, UV and conventional inks; being able to run metallics and white inks without changing the fountain solution; and significantly reducing the cost of hauling away waste fountain solution.


Eric A. Gutwillig and Tony Prieto are the vice president of marketing and Western regional technical manager, respectively, for Printers’ Service (Prisco). Contact them at www.prisco.com.