Linting or Fiber Separation

  The Problem:

The cover is shedding excessive fibers or "linting" which is affecting the print quality. The fibers are building-up on the ink rollers and/or the plate.

  The Possible Causes:

Several factors can cause fiber separation. One general statement that can be made is that cotton covers are much more prone to this problem than synthetic covers. The reason is that cotton yarn is not a continuous fiber but rather it is made up of multiple lengths of yarn called "staples". These short pieces are intertwined or spun into a length of yarn. (A comparative example of this type of construction would be hemp rope).

Dampening covers made from synthetic yarn, most commonly rayon, are less prone to breakdown and the resulting linting. Man-made fibers are continuous in their construction so there are no individual lengths of yarn to become separated. A comparative example of this type of construction would be fishing line.) By the way, Novatech uses only synthetic yarns in all of its products.

Even given this distinction in yarn type, both types of covers, however, can suffer from fiber separation. The most common causes are excessive water form roller-to-plate pressure and/or high ink tack. (The form roller cover is almost always the culprit  as the ductor cover does not make contact the plate nor does it undergo as much contact abrasion). Another cause can be too aggressive cleaning.

  Suggested Solutions:

• Reduce the form roller-to-plate pressure: Excessive contact pressure to the plate can cause a variety of problems, fiber separation among them. Set the roller pressure as light as you can without affecting moisture transfer. A suggested method for setting the pressure is available for your review.
• Reduce the ink tack: Add a tack or ink reducer to the ink. This will minimize the inks' tendency to strip the fibers off the cover.
• Try less aggressive cleaning techniques: If you are cleaning the covers by scrubbing with a brush or squeegeeing the covers dry with a sharp instrument (an ink knife blade is a favorite among press operators) try a less aggressive method. Hot water under pressure will do a more efficient job of cleaning as well as minimizing abrasion.