Waterless Printing Provides Reduced Dot Gain, More Consistent Color

All print buyers and designers seek high quality, accurate color reproduction. When printing with the conventional offset process, the requirement to balance fountain solution with the ink is naturally detrimental to the quality of the printed piece.

This is because the fountain solution dilutes the ink and causes the printed dots to soak into the paper and spread. This inclination for dots to spread in size is called dot gain. When printing with the Presstek PEARLdry plate and the Toray Waterless plate, dot gain is reduced.

Notice how the dots rendered with a Toray plate (left) are much sharper than those printed conventionally.

In the case of conventional printing, the dot gain phenomenon is why standard screen rulings are usually limited to 200 lines per inch(79 lines per cm) maximum.

Because there is no fountain solution used in waterless printing, dot gain is reduced significantly. Toray waterless screen rulings of 300 lines per inch (120 lines per cm. ) are common, while some waterless printers offer screen rulings of 400 lines per inch (157 lines per cm) and higher.

Another aid to reduced waterless dot gain is the intaglio construction of the plate itself. Both plates feature "ink receptive wells" rather than a flat, ink receptive surface. These wells provide supportive walls for the ink as it is transferred from the plate to the printing blanket.

	Printing without water with specially designed waterless plates offers more photographic detail. Shown above are dot gain curves using negative working plates.
	Positive working plates offer even more dramatic reductions in printed dot gain.

With up to 50 percent less dot gain than conventional printing, print buyers and designers can expect to print much more photographic detail. This means far more clarity, especially in shadow and midtone areas of the picture.

Waterless printing COLOR SPACE is bigger than conventional printing because the printer can lay down a thicker ink film or densities. Higher average ink densities of 20 percent or more have been documented. Printing with higher screen rulings can expand this color space even more by applying more ink to the printed piece. This combination of higher ink densities and sharper dots also allows for much higher print contrast than can be achieved with conventional lithography.

In addition, printing without water or fountain solution yields higher levels of print quality on uncoated and recycled papers. This is achieved through a reduction moisture induced paper linting and better ink holdout through less ink absorption. These qualities generally eliminate the need for multiple color passes and touch plates. Registration is improved because paper stretch caused by fountain solution is eliminated.

Non-absorbent substrates such as plastics, metal and synthetic papers have traditionally presented problems for conventional offset. Because there is no water take-off, water tends to track back up into the inker causing a higher degree of emulsification and adding to fluctuations in print consistency. The waterless process offers a greater degree of control in printing on these substrates.

Finally, through the elimination of the need for ink and water balance, the largest variable is removed from the printing process. As a result, printing without water offers a much higher degree of color consistency throughout the pressrun.

The WPA helps members keep up with the latest developments in Waterless printing. Find out how WPA MEMBERSHIP can benefit you.