Ink Transit (Gravure)

Gravure industry insiders tackle key issues for optimum ink transfer and reveal equipment developments aiding the cause.

by Jessica Millward, Associate Editor

Blade basics

Though gravure printing's consistency and dependability as a printing process are well-publicized, press operators should keep a close eye on doctor blade configuration. Max Daetwyler Product Sales Manager Marty Cansler affirms, "What is often crucial for consistent print quality is the ability of the doctor blade to provide clean and even ink application during the entire print run."

As he elaborates, maintaining the blade contact area is integral to controlling such print defects as hazing and color variation. Contact area is easily affected by changes in blade contact angle and in blade pressure, so the easiest solution is to keep contact area to a minimum. To do so, Cansler suggests using a thinner tipped blade, which produces a clean wipe, and wears less on both blade and cylinder. Because of their mechanical loading devices, older presses may not be suited for this type of blade, in which case Cansler recommends a long, tapered bevel blade.

Not too dry

Dry ink within the print cylinder presents another foe to effective ink transfer. Frank Passarelli, product business manager at Bobst Schiavi, shares his company's method for keeping ink fresh: "Encapsulate the printing group area to allow for an atmospheric condition that increases the solvent concentration within the encapsulated area." This technique avoids dry ink by keeping the cylinder humid after the printing nip. Passarelli maintains in doing so, press operators will avoid solvent evaporation from the residual ink inside the engraved cells.

Not too wet

Electrostatic Speed Assist (ESA) systems, designed to enhance ink transfer, aren't exactly a new development, but it is in recent years that they have become almost ubiquitous on gravure presses. However, Steve Siler, director of engineering at Hurletron, notes while ESA is often necessary for good ink transfer, the process may not be sufficient with some substrates.

Siler explains ESA works by raising the ink surface in the cell above the surface profile of the cylinder, which facilitates contact between ink and substrate. The difficulty lies in water-based inks.

"Water-based inks leave a slightly 'damp' substrate," says Siler, "It is commonly understood that damp webs do not readily hold electrostatic charges." While power supply currents can be increased for effective ESA usage in some cases, in others, the formulation is simply too conductive to support the necessary electric field.

Speed prequel

When running any substrate at a higher speed, both doctor blade and inking concerns become especially critical. Windmoeller & Hoelscher President Hans Deamer believes it is essential to employ a pre-inking system for such circumstances. Some of the best systems, he elaborates, "…utilize a combination nozzle with a special driven rubber roller, which squeezes ink into the cells, and pre-wets the cylinder immediately after ink transfer and before the cylinder is immersed in the pan." High-speed cavitation, as well as streaks caused by air entrapment in the cells, are thereby eliminated.

Press parlance

Bobst Schiavi has incorporated motorized doctor blade assemblies on its latest gravure press models, including the Idea, to provide for optimum ink transfer. The units are equipped with two stepping motors and two pneumatic pressure cylinders, which permit a wide range of wiping angles.

Nik Kuppalli, marketing director at Inta-Roto, reports his company's gravure presses now employ an automatic pH and viscosity control system to constantly update ink and keep it at a consistent level.

Spring's CMM International witnessed significant supplier strides in gravure technology. Chesnut Engineering introduced its COMPACT Series narrow-web flexo/gravure press, developed for short-run production. Windmoeller & Hoelscher demonstrated its HELIOSTAR® printing station, featuring the ECO-PLUS® automatic wash-up and cylinder changeover system. Finally, Valmet Rotomec displayed its Electronic Shaft (ES) system, which precisely controls cylinder position on new models of the 3000-5 to 4000-3 presses.

L-M leads Gold rush

Atlas Wine Merchants' Millennium edition 2000 President Cuvee champagne bottle needed to be appealing enough to increase product sales, and, as a specialty packaging line, to be produced as cost-effectively as possible. Atlas charged the task to Lawson Mardon's (formerly Algroup) Toronto/Weston plant.

Site Manager David Sinden recalls the graphic approach focused on the historical nature of the millennium, appealing to the Canadian identity and President brand for existing and potential customers. Already popular with Canadian consumers in the low- to mid-market range, the superior visual look of the bottle was meant to dissuade customers from choosing more expensive champagnes for millennium celebrations.

Packaging designers concluded the best approach would involve a full shrink-sleeve label application for total coverage. The full-size label necessitated no change to either the existing bottle or shipping carton dimensions.

An original David Craig oil painting was selected as the primary visual element of the label. The Lawson Mardon team believed gravure was the obvious choice to both replicate the painting and incorporate the required shrinkage for the PVC shrink film. Sinden also notes, "The additional requirement for a rich, matte gold ink laydown made gravure the best choice."

Produced in eight colors on a Schiavi press, sales of the champagne grew 40 percent. Lawson Mardon was asked to create a 2001 version of the label, and the Gravure Association of America, similarly impressed, handed the label the first ever "Best of the Best" Award in the 2000 Golden Cylinder competition.