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Home > News > Web Offset > Offset vs. Gravure

High-volume commercial offset or publication rotogravure

Renewed rivalry between two processes

Veteran gravure printers swear by this proven process and in recent years have been putting their money where their mouth is. But big industrial web offset printers, for whom gravure may well be cost-effective, tend to fight shy of making the transition because of the need to build up a whole new infrastructure around the press. While reservations concerning the technological intricacies surely play a role in hindering adoption, it is not the only factor.

Publication rotogravure has the advantage of webs up to 4.32m wide and an automated workflow (2)

Advances in web offset and publication rotogravure technology over the past few years have fuelled the ongoing debate on the relative strengths and weaknesses of the two processes.

Gravure presses, which are now capable of handling webs 4.32 metres (14ft 2in) wide, and whose format flexibility is legend, are constantly setting new standards in productivity. However, leading manufacturers of offset presses have not been idle and have long since succeeded in increasing web widths to more than 2 metres (6ft 6in). They are now audibly contemplating even wider webs.

Fast pre-press turnaround

Take pre-press, where offset has traditionally had the advantage. In gravure, the adoption of digital processing streams and data conversion directly in the engraving line has not only delivered substantial time savings in handling print jobs but also contributed to a further enhancement in print quality. Tonal transitions are finer and type edges smoother than ever before. As a result many gravure printers in Europe have succeeded in making a profit from printing relatively short run lengths (for gravure) of between 200,000 and 300,000 copies. The advanced level of automation in both press and pre-press means that in most cases the digital proof is now perfectly adequate and there is no need to print a proof on the press.

Variable format cuts paper consumption

As far as paper consumption is concerned, gravure has a clear edge over offset because forme-cylinder circumference is variable and can therefore be adjusted precisely to the specified format. What is more, there is no need to allow a margin for pins. This places offset printers at a disadvantage on two counts. First, when investing in new kit, specifying the format is a tricky business since it is almost impossible to predict future demand, whereas a gravure printer has no difficulty in accommodating different formats at a later date. Second, when estimating a job, offset printers have to factor in a much higher volume of waste, and for twin-web production a higher volume still. An additional drawback with double-circumference presses, apart from the higher paper consumption, is that if one ink-knife setting is adjusted, all four pages around the circumference are affected by the correction, although only one page is supposed to be changed.

Imprint changes for split editions

The sheer variety of product layouts possible with gravure derives from the combination of superstructure and folder variability. By systematically exploiting gravure’s specific advantages it is possible to make a successful incursion into the commercial sector. It even affords certain benefits for the production of high-volume advertising supplements, which normally have a low page count. Such products can be printed cost-effectively and fast in multiple production on wide gravure presses using two or even three formers. The addition of one or two flexo imprinters enables flying imprints (eg changes of language) to be made at maximum production speed. Exploiting gravure’s flexibility in this way often allows such presses to be used for runs of well below one million copies, which opens up the growing market for low-pagination products.

A comparison of production speeds shows that gravure still has the advantage, especially if calculations are based on net output. The gravure printing process is less problematical than offset, which is complicated by the use of ink keys and dampening units. As for folders, the advances in offset that have enabled production speeds to be noticeably increased and production made much more flexible (eg KBA’s variable-format V5 folder) are due in large part to the adoption of sensible technologies from gravure such as grippers or 5:5 and 7:7 cylinder ratios.

Environmental impact

Waste prevention and energy conservation have moved steadily up the agenda in recent years, not least because of tougher environmental regulations and spiralling energy costs. In future there will be a continued focus on limiting emissions of volatile organic compounds (VOCs) in order to reduce air pollution. During the offset drying process almost the entire mineral oil content in the ink is forced out of the paper and the crude gas burnt off in a thermal exhaust-gas purification unit. Despite the reduction in alcohol content in the fount solution, the total volume consumed is often still very high. The washing processes for the inking units and the blankets also give rise to a high volume of emissions. In gravure, toluene is used as a solvent in the inks, since it not only dissolves the binding agents extremely effectively but also evaporates rapidly with a small input of energy in the dryers and can be almost completely recovered using adsorption filters filled with activated carbon. The recovered toluene can be re-used within the printing plant to thin the ink or resold to ink manufacturers – the perfect recycling system.

Summing up

Advances in web offset and publication rotogravure technology over the past few years have fuelled the ongoing debate on the relative strengths and weaknesses of the two processes (1)

The cheapness of plates and the speed with which they can be made gives offset the advantage where low-pagination, low-circulation products are to be printed. But when it comes to low-pagination advertising supplements and flyers with high circulations, gravure could be the better alternative from the economic point of view. Whether a print job would be produced more cost-effectively in gravure or offset must be calculated on a case-by-case basis – there is no clear delineation for the logical use of one process or the other. In general, it may be said that gravure may well be economically viable for copies with a low page count but a high circulation, or a low to medium circulation but a high page count. The benefits of gravure increase if copy size deviates from standard offset formats, since there is then no unnecessary paper waste. The higher cost of the engraved cylinders is balanced by savings elsewhere, most notably in personnel and paper. The biggest gravure printing companies can also exploit the economic benefits of standardised, high-volume print production, streamlined operations and national sales networks, whereas web offset printers tend to operate at a more regional level.

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