DAMPENING SYSTEMS -- Striking a Balance
According to the manufacturer, pressroom temperature is another variance factor and can impact the amount of water delivered by open dampening systems, which rely on surface tension for transfer. Similarly, contamination is of particular concern with brush dampening systems, the position paper continues. Ink-matted bristles will not transfer water properly, so the operators start cleaning the brushes with blanket wash, which winds up in the fountain solution and can lead to scum, toning and tint problems.
On a web press, switching to a new spray dampening system can improve print quality by reducing dot gain, boosting contrast, producing better gloss and providing a more consistent ink density, the manufacturer says. Time savings come from faster makeready and setup, combined with reduced downtime and maintenance requirements, it adds.
Dallas-based Accel Graphic Systems offers dampening systems designed for smaller format sheetfed offset presses. The nature of that market means that tradeoffs between press features and costs usually have to be made. Therefore, advances in technology have made new and existing presses prime candidates for upgrading to continuous dampening systems, points out Lance Carpenter, Accel's general manager.
For this segment of the industry in particular, the press operator's skill level can be a factor in choosing the right dampening system, Carpenter asserts. "The simpler the system is to operate, the easier it is to increase the quality of printing and produce profits," he says.
"System" is an operative word in the discussion, says Thomas Haas, vice president of technology at technotrans america, sheetfed division, in Corona, CA. "Effective control starts with the incoming water supply and encompasses the proper dosing of the fountain solution and additives, proper mixing of the solution after dosing, temperature control, rate of water flow/exchange and filtration, to name a few issues," he argues.
Many presses still use fountain solution circulation systems with 1960s-era designs, Haas says. "Most older sheetfed and web presses were installed with simple, single-tank recirculation units that provided cooling of the water, as well as circulation to and from the press water pans, along with very basic and fairly inefficient filtration," he points out. Thus, printers stand to benefit by upgrading from this technology.