What is Waterless?

Waterless printing is an offset lithographic printing process that eliminates the water or dampening system used in conventional printing. It uses a special silicone rubber coated printing plate, special ink, and typically a means of temperature control on press.

In waterless printing the process of printing is changed chemical one involving the use of Isopropyl Alcohol or their substitutes to a simplified mechanical process. Instead of the press operator balancing the delicate relationship between ink and water, all that waterless printing requires is a temperature range for transferring ink to the substrate.

Currently two manufacturers produce printing plates that work without water. Toray, a company based in Japan, makes a photosensitive analog plate that requires film, exposure and processing as well as a computer to plate product currently named Emerald. As of November 1, 1999, a third manufacturer, Kodak Polychrome Graphics, has a digital waterless plate in beta testing.

Another computer to plate product which does not require film or processing is offered by Presstek Inc. of Hudson, New Hampshire. Presstek calls its product PearlDry. The PearlDry waterless plate is used in a growing number of DI (Direct Imaging) printing machines such as the Heidelberg QM-DI, Omni Adast DI as well as the new Karat 74. These machines serve the fast growing needs of the on-demand print market for short run four color printing.

Screen rulings offered by these presses are 150 lines per inch (60 cm) up to 200 lines per inch (80 cm).

Presstek’s PearlDry plates are also available with aluminum backing for imaging off-press on a variety platesetting machines. These printing plates are used on printing presses as large as 40 inches (102cm) with maximum screen rulings of 240 lines per inch (94 cm). A new product called the PearlDry Plus is capable of 300 line per inch (120 cm) screen rulings.

Waterless printing plates offer quick roll-up to color and thereby reduce set-up (makeready) paper waste. Chemically tainted waste water from traditional offset printing is also eliminated. Waterless plates are capable of extremely high screen rulings and, as a result, apply more ink to the printed piece. This results in a much larger range of colors in four color process printing. A waterless plate is an intaglio plate not unlike a gravure printing plate. Images to be printed are actually recessed from the surface of the plate. Since the water dampening chemistry is taken away, the printing ink cannot become emulsified. Thus, cleaner, sharper images are made possible. Toray’s waterless plate has been known to render screen rulings of up to 900 lines per inch (354 lines per cm).