Spot-on colour from magnificent seven

By Barney Cox, Monday 29 September 2014

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Two of the key requirements for the colour reproduction of packaging print are for the products to fly off the shelves while the colour stays on-brand.

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Historically, special colours have been used to meet those requirements, overcoming the limitations of CMYK process inks, namely a limited gamut and lack of consistency. 

But while special colours solve those problems they bring their own restrictions. Each one needs its own printing unit, which limits the number that can be used per job to the number of units on the press. Also, colours are unlikely to be the same from job to job, which means at every job change the printer needs to wash up each unit and change over the ink. 

“If you need to do job changeover with wash ups to change ink colours you’re talking 45-50 minutes, even on the latest presses,” says Heidelberg UK product manager Paul Chamberlain.

In the past when run lengths were in the tens or hundreds of thousands, that wasn’t a problem. But in packaging, as in the rest of the industry, runs are coming down from tens of thousands to thousands or even hundreds, which makes those changeovers much more significant.

“The drivers are more line variations, brand extensions and moves to lean processes, including just in time delivery and reduced inventory,” says Esko Equinox product manager David Harris. “As typical orders become shorter, the spot colour workflow becomes less efficient. Press utilisation can be as low as 25%-30% on short runs as they spend the majority of their time being prepared for the next job. Plant managers are looking to reduce costs. Digital is one answer, but it’s not economic for all work.” 

Are there any other options?

While digital printing may not be the answer, a technique that is used on digital presses is. Extended colour gamut (ECG) printing adds colours to the standard CMYK inks – typically orange, green and violet – and makes separations using all the colours, which greatly extends the reproducible gamut.

“If you keep a fixed ink set on the press all the time the job changeover time is dramatically reduced, which increases efficiency and utilisation,” explains Harris. “One customer was thinking of buying another press to improve throughput before implementing ECG. The ROI is well inside a year.” 

Haven’t I heard this before?

Those with long memories may have a feeling of déjà vu. ECG is not new, even if the acronym could well be. 20 years ago the industry was in a frenzy of excitement about Hi-Fi colour, which is ECG with a 90s-style name. Back then it was Pantone’s Hexachrome system that led the way – a special CMYK ink set with orange and green. Alas Hi-Fi colour went the same way as the hi-fi in most living rooms.

According to Alwan Colour president Elie Khoury, Hexachrome didn’t take off first time around because “the industry wasn’t ready, there wasn’t enough process control on the press to optimise and maintain the gamut”.

So what’s different this time?

The market has moved on. Not only have the drivers for adoption become more pressing, the issues that undermined Hi-Fi colour have been fixed, paving the way for ECG to be adopted.

“ECG has been widely used in digital for several years – our partnership with HP Indigo dates back a decade,” says Harris. “Most brand owners have some of their range digitally printed and they can see that the results of ECG meet the necessary standards.”

It’s not just the emergence of digital that has changed, there have also been developments in the technology and working practices in the industry as a whole, which make ECG appropriate for litho, flexo and potentially even gravure printing.

“A couple of things have happened in the last couple of years in flexo,” says Pantone Digital solution architect Jeffrey Hall. “Flat top dots and microcells have improved solids and fine highlights.” 

Higher flexo screen rulings have also reduced the ‘graininess’ of tints, making it less obvious a colour is separated rather than a solid special.

Process control is also crucial, especially for offset, which is emphasised by Heidelberg’s Chamberlain. “The press needs to be printing to numbers,” he says. 

The adoption of ISO 12647 in commercial print and the methods of implementing it, whether Fogra, Ugra or G7, mean there is no shortage of numbers to print to nor a lack of understanding of both why and how to do it.

What are the challenges?

For ECG to work it also has to be embraced and understood throughout the supply chain, from the brand owner, through the designer and repro house, all the way down to the printer. 

While there are many benefits of ECG over spot colour for printers, fortunately there are also advantages for both brands and designers too. On top of that the recent introduction of PantoneLive to address some issues in the specification, communication and reproduction of special colours has made the whole supply chain more aware of the problems and as a result more open to ways of addressing them.

According to Pantone Digital’s Hall it’s the time saving that will really appeal to brands: “Getting to market can be much quicker. You can get products onto the shelves in months rather than quarters.”

For Esko’s Harris one big benefit is that ECG will set designers free, rather than rein them in. “Designers are currently restricted in the number of colour ways in a spot colour workflow. In ECG it’s not the number of colours it’s the size of the colour space. Designers can use any colour within the gamut – and it’s easier to match across print processes,” he says.

What are the enablers of ECG? 

One crucial element of successful implementation is getting the colour separation right. There is already software on the market to make ECG separations, and more on the way. Currently Esko’s Equinox is leading the way, but other products are available, including Alwan Color Suite, Kodak’s Spotless. Heidelberg’s recently announced Prinect Multicolor Toolset and ICISS from Aurelon, which first came on the scene in the first blush of interest in Hi-Fi colour in the 90s. Other tools include Opaltone and FM6.

Regardless of the tools used it’s helpful to understand the fundamental principles of colour reproduction.

“It’s about transferring best practice from ink mixing to separation,” says Hall. “Essentially you’re doing ink formulation in pre-press instead of the ink kitchen.

“Never mix more than three colours in a separation to make sure you’re not creating the equivalent of an overly complex ink formulation in separation,” he adds.

Get it right and, as in four-colour printing, good separations help ensure on-press performance.

“Results from customers show that a seven-colour process is no more unstable on press than four-colour,” says Harris. “Indeed, research by Clemson University in the US has shown that seven-colour printing can be more stable as the separations tend to use fewer inks to make a particular colour.”

In which processes is ECG applicable?

ECG is process agnostic. It’s already the norm in digital and the benefits are applicable to any process, although the biggest benefits come from those used for shorter runs, so offset and flexo are the current focus.

“We see adoption in offset and flexo,” says Harris. “In offset for labels and folding cartons and in flexo for narrow- and wide-web printing.”

There are technical reasons why it’s relatively easy to implement ECG in flexo and offset. In the case of flexo it’s because the print process is inherently stable, while in offset the widespread use of closed-loop colour control on press ensures a similar level of process stability. 

Pick a colour

While Hexachrome stipulated special CMYK and orange and green inks, ECG is more flexible about the colours used as gamut extenders. From a colorimetric perspective, seven inks seems to be the best way to go, adding orange, green and violet to CMYK. Rather than using special CMYK, most firms are using inks that conform to ISO 2648, which defines the characteristics needed for working to ISO 12647, enabling firms to work to existing standards where appropriate.

In an ideal world then, anyone implementing ECG would have a seven-colour press and would load it up with CMYKOGV and get cracking. Back in the real world things aren’t so simple. While most flexo presses have seven or more units, so can be configured this way, most offset presses employed in packaging print are six-colour and some are five, so a compromise needs to be found on the gamut extenders to use. Fortunately it’s likely that in most instances a workable compromise can be reached.

“Rarely will you use all seven colours for every job,” says Hall. “Nine times out of 10 you won’t need all seven, and 50% of the time you probably only need five.”

Harris adds: “You can still implement ECG but you need to choose the extra colours carefully. Check your jobs to determine the most commonly used spots and select the most appropriate extenders to match them.”

While it will still be necessary to carry out some wash-ups, by batching similar jobs together, they can be reduced compared to when using a spot colour workflow. So it is still possible to significantly increase press utilisation. 

What is the current level of adoption? 

In the US, which is ahead of Europe in ECG adoption, the Flexographic Technical Association (FTA) stated that for 2013 10% of printers were producing more than 50% of their work ECG. And some sites are solely ECG, according to Harris.

But you don’t have to completely shift over to ECG to see a benefit, which should give printers and brand owners the confidence to test the waters without too much risk before taking the plunge.

“Some work is very easy to convert and just one client can provide the ROI,” says Harris. “You don’t need to switch over 100% of work to get the benefits.” 

That said, in the long term for all but the most challenging combinations of colour, process and substrate, ECG looks likely to be as commonplace as CMYK.

“I feel that initially 50% of jobs using PMS are suitable for immediate switching,” states Alwan’s Khoury. “In the long term it will be more like 100%.”  

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