Extended colour gamut in gravure printing

Many people in packaging gravure are sceptical or even dismissive of “7-colour printing”. It is “technically not possible” or “our customers won’t accept it” are the arguments given. But what are the reasons for this attitude? What possibilities for further cost reduction and stabilisation of production processes does extended colour gamut printing offer for the gravure process?

Many technical experts have been working in the packaging printing industry for a very long time and therefore still vividly remember the stir caused by the introduction of Hexachrome from Pantone in the late 1990s and Opaltone in the early 2000s. However, neither of these colour separation system was able to establish itself in packaging printing – and rightly so.

Development of multicolour separation

Hexachrome is a 6-colour system based on the primary colours CMYK plus an additional orange and green. However, the saturation of CMYK was also significantly increased to ultimately be able to achieve 90% of the Pantone colours. In addition, there was a corresponding ICC profile to use for the separation.

The Opaltone system is designed for 7-colour printing and consists of the basic colours CMYK as well as red, green and blue. In addition, it has its own matching system (Opaltone Matching System), which, however, does not correspond to that of Pantone (PMS).

Hexachrome and Opaltone are very proprietary or closed systems that are difficult to integrate into gravure prepress workflows. For both, plug-ins for Photoshop were offered for purchase according to a corresponding licence model for the re-separation of the data.

However, the costs associated with this were quite high, as combining these two solutions with the industry software used was very cumbersome and time-consuming. But this statement primarily refers to Europe, as in the USA – at least at that time – a different software design prevailed.

Though, a lot has changed in the past 20 years and therefore the initial position for 7-colour printing is different today. Currently, there is more discussion about “Extended Colour Gamut” (ECG), which basically corresponds to the idea of 7-colour printing. Today, ECG usually means the colour composition CMYK, orange, green and violet.

In principle a simple process

In principle, the use of a 7-colour system in prepress is a simple and mostly already integrated process. Almost all suppliers, such as Esko, Hybrid Software, GMG, ORIS or ColorLogic, offer appropriate solutions for separating the data. In some cases, re-separation is already carried out in the corresponding editor when the data is prepared, or an automatic workflow is used that transforms and re-separates the finished single-up images into the ECG colour space.

With both solutions, the separation logics can be adapted to the respective needs in order to control the result or the structure of the separations. There is no additional licence fee as with Hexachrome or Opaltone.

In addition, today’s colour management solutions offer the possibility of creating multicolour profiles – i.e. colour profiles for more than four colours (CMYK). Analogous to the familiar process colour profiles, test charts are printed under the respective printing conditions and converted into colour profiles by means of a certain software. These charts consist of seven colour channels which area also used to characterise overprinting on the respective substrate. Based on these profiles, digital proofs can be generated that simulate the expected print results in the 7C colour space.

This is a clear advantage over the generic colour profiles used by Hexachrom and Opaltone, because they do not reflect the variability of substrates and ink systems used in packaging printing. Thus, a digital proof has only little informative value with regard to the realistic representation of the expected print result.

Furthermore, unfortunately there is still no international standard for 7-colour printing. However, Fogra, the German not-for-profit institute working to support the printing and media industry, is working on a corresponding standard (ISO 21328). This is intended to establish corresponding framework conditions that can serve as a basis for printing in the extended colour space.

Predestined for 7-colour printing

In terms of print stability and repeatability, the gravure process is predestined for standardised 7-colour printing because the printing cylinders are produced in a fully automatic inline process and hardly show any tolerances. In particular, fast-response control technology and the metallic printing cylinders ensure very high running stability in gravure presses.

The susceptibility of packaging designs to register inaccuracy during the production run and the resulting colour fluctuations is often cited as an argument against the use of 7-colour printing in gravure, since almost all elements have a multicolour structure. Above all, fonts and line elements that fall short of a certain minimum thickness make it difficult to print in register.

But the truth is that these register difficulties apply also to 4C printing. Moreover, the creation of trappings and underfills for 7C printing is done in the same way as for 4C build-up. In some cases, the use of orange, green and violet even makes trapping less noticeable than in 4C printing.

In today’s gravure package printing, the rule is that images are separated in the process colours (4C), while logos, fonts and possibly fonts and line elements are created as spot colours. But logos and fonts in particular often have to be built up in combination with 4C in order to achieve the respective colour template. But even such kind of elaborate packaging is produced today in the highest quality and with high reproducibility. This is why register and colour variations are just as problematic or unproblematic in 7C printing as in 4C printing.

What actually are the obstacles?

The conversion to 7-colour printing requires intensive preparation, which must also include a feasibility study.

Before undertaking such a project, the basic strategy must be determined. Is it perhaps possible and sensible to earmark a press for permanent use of 7C printing? Is the project to be realised with a defined customer? Should all jobs or only a specific series of jobs be converted to 7C? Or is 7C to be used as a unique selling point for the acquisition of new customers?

The goal of these preparations must of course be potential cost savingy. No major investments are necessary for the initial probing, but investments in test formes, machine time and consumables must be made to create a resilient basis for decision-making.

The main savings potential lies in the area of set-up costs. In addition, it is possible to work with collective formes in order to increase the print quantity per job. Collective forme in this context means printing different motifs of a job series. For example, there are cases where it is more effective and cheaper to engrave a new set of cylinders every one or two weeks and to compile the individual one-ups in the layout according to the needs of the brand owner.

If, after evaluation, the printer concludes to introduce the 7C printing process, the end customers (brand owners) must be involved in this decision-making process at an early stage. Ultimately, the switch to 7C is only successful if everyone benefits from the resulting savings. Moreover, the end customer is in a position to positively support the realisation of such a project. This is because when creating new packaging designs, the separation in 7C and thus the printability can be simplified in the creative phase by observing a few rules.

Some global brand owners have worked out appropriate concepts with printers and pre-press companies and have built up their packaging designs “7C-favoured”. Often only minor adjustments have to be made for 7C printing, for example by creating fonts in black.

If existing packaging motifs are to be converted to 7C, the first thing to check is to what extent the spot colours used can be achieved through the extended colour gamut. However, since packaging is already on the market, colour deviations are only accepted within narrow tolerances.

It can be assumed that colour variations will occur when using 7C. However, printers should compare these tolerances self-critically with the previous status quo (4C plus special colours). Because even the current use of spot colours is subject to colour deviations. Therefore, these possible tolerances should be openly communicated to the customer and the saving potentials associated with 7C printing should be pointed out.

Conclusion

Printing in an extended colour gamut (7C), together with its process advantages, can offer gravure printers great saving potentials. Even though a cost reduction may only be achieved for 20-30% of the print jobs, it is still usually worthwhile for a gravure package printer to work with a fixed colour palette. Moreover, the gravure printer can fully exploit the advantages of 7C printing in the next big tender offer of a branded goods manufacturer and finally acquire the order package.

 

Björn Kammertöns

is a proven expert in colour management, gravure and package printing. He advises and supports brand owners and print shops in the realisation of their print products. Contact him if you would like more information or would like to realise a project with him: