Label buying can be a bit of a minefield for those who aren't experts. Barry Hunt goes back to basics to give a lesson in label production

How important is it to know how labels are produced? Judging from what label converters say, the big buyers think it is vital. They usually have a sound knowledge about production techniques and materials of a broad range of label and packaging products.

This professional approach goes a long way in choosing suppliers that can deliver high standards of quality and service. But this is an article for those buyers who have only the sketchiest knowledge of label production methods – or how the pressure sensitive (self-adhesive) labelling sector fits into the scheme of things – and would like to know more.

The first thing to note is that labelling comprises a dozen or so different label types, of which the dominant self-adhesive sector is the most innovative in terms of materials, methods and applications, which makes for a highly fragmented business. Trade sources suggest that self-adhesives account for around 55% of the total western European label volumes, following unbroken growth for over 35 years.

The main loser here is the traditional glue-applied sector, due to changes in both packaging methods and retail buying habits. Universal growth in convenience foods has reduced demand for paper labelled cans. Similarly, more wine producers and drinks companies have turned to self-adhesives labels to reflect changing patterns of distribution and marketing trends, such as using transparent filmic labels to obtain a ‘no-label look’.

Glue-applied labels are usually printed on large-format sheet-fed offset presses, followed by bronzing, embossing, punching or cutting as separate off-line processes.

Heavy investments in integrated canning or bottling lines and high production standards will ensure it remains a major technology for the foreseeable future, maintaining around 30% of the total label market in Europe.

Since the early 1990s, both the self-adhesive and glue-applied sectors have lost some business to the ‘non-adhesive’ technologies: in-mould labels (mainly for dairy and household products and motor oils), paper or film wraps for carbonated drinks and mineral waters and shrink sleeves for various toiletry and health care products. Their usage reflects an overall growth in the usage of plastics containers.

Environmental considerations have also encouraged the wide use of thinner multi-ply polypropylene and polyethylene films with improved barrier characteristics.

Although their total market share remains relatively small, they can give packaging designers useful options when labelling plastics containers. Wrap-arounds and sleeves in particular offer scuff free pack protection, 360-degree coverage for point-of-sale impact and a choice of tamper-evident features.

Returning to self-adhesives, most primary product labels are supplied in printed and die-cut rolls ready for use on automatic label applicator machines.

Production involves roll-to-roll presses, commonly in widths of from 250-520mm – hence the term narrow-web – although a crossover into packaging applications has resulted in mid-web presses with widths up to around 720mm.

It is a highly versatile printing method and makes an ideal partner for the countless permutations of pressure-sensitive paper and filmic laminates (facestock, adhesive and release liner). Depending on individual technical characteristics, die-cut labels can be specified to adhere to freezer packs or remain in place on squeezable shampoo bottles.

By the same token, there is a big difference between laser-imprintable data labels for tracking industrial products to transparent or opaque filmic labels. Any competent converter can advise on the available choices but the inherent complexity of the subject further reinforces the need for buyers to understand the basics.

In terms of production techniques, the past decade has seen some significant changes, centred mainly around more affordable and reliable electronic devices to control the tension and infeed of materials. Some presses boast remote inking using preset parameters to ensure colour consistency.

Quick, toolless changeovers of ink ducts and print cylinders using slide-out print stations allow fast set-ups between jobs. Many press systems allow plates and inks to be changed for new jobs while running another. Customers may not be aware of this increased sophistication, but it has allowed converters to drastically reduce lead times and maintain higher print standards across a wider choice of labelstocks.

Another advantage of narrow-web technology is that it offers a choice from all the mainstream print processes, either singly or with two or more processes. Although still highly regarded for premium-quality labels, rotary or semi-rotary letterpress has lost ground since the early 1990s throughout much of Europe. Conventional flexography using water-based inks is now the most widely used process, as it is with wide-web flexible packaging. Improved flexo inks, photopolymer printing plates and more efficient anilox rolls have raised all round quality levels.

UV flexo shares similar printing techniques but the use of UV-curable inks makes it a quite different process. After a slow start and much hype, the process is now gaining acceptability at the high-quality end of the narrow-web label and packaging markets. The fact that the inks dry almost instantly to give a hard, glossy surface also results in small, sharp half-tone dots for smooth screen gradations, including vignettes.

Higher capital and running costs and the need for clean running conditions mean it is not necessarily a realistic replacement for conventional flexo for mainstream applications.

The widespread popularity of combination press lines, which involve more than one printing process, has provided a platform for UV flexo as the main process. Invariably it is combined with UV rotary screen and/or hot-foil modules to achieve eye-catching graphic effects.

The really high-end process is UV-cured rotary offset using conventional metal plates. As in commercial printing, offset (or litho) is capable of the very finest printed effects and benefits from decades of progress with pre-press systems.

The image is literally ‘offset’ from the plate to a rubber blanket and then transferred to the substrate, which passes through the blanket and impression cylinders. This allows a greater choice of less smooth or textured labelstocks. Thinner ink films and lower printing pressures give reduced dot gain and good colour consistency.

Although a minority label process, it has gained ground in some specialised premium-grade markets, especially wines and spirits, as well as cosmetics and toiletries.

Offset-based combination presses feature interchangeable print and die-cut units for job flexibility and fast set-up times, which allow both short and long runs. Gravure modules have begun to appear as an alternative to using off-line silver or gold bronzing machines, as used with sheet-fed offset label presses.

It is worth noting that the manufacturers of air or water-cooled UV curing systems have made enormous technical strides. Modern compact systems (essential for fitting in the tightest of spaces) are now more efficient in terms of matching the spectral output of UV lamps with the specially formulated inks at higher press speeds.

Better heat management options, including water-cooled chill rolls, have proven their worth with heat sensitive labelstocks, including unsupported films for shrink sleeves, wraparound labels and other flexible packaging.

Converting the thinnest of unsupported films on narrow-web presses is now an established practice. Servo-driven web guides and tension controls between individual print units accommodate varying substrate thicknesses, all under automatic register control. Often this type of press includes both hot-air drying systems for working with solvent-based inks and UV curing systems.

The addition of water-cooled plates or servo-driven chill rolls behind the substrate facilitates the handling of these heat-sensitive materials. Film presses allow label converters to diversify into producing flexible packaging products.

A new development is for companies to offer a narrow-web trade printing service or, in some cases, form partnerships with wide-web flexo and gravure printers to handle short runs that would be uneconomic on larger presses. Reel-fed presses designed specifically to produce small folded cartons, complete with die-cutting and edge trimming for finished carton blanks, represent the other side of the multi-function coin.

The main advantage is operating efficiency since everything is done in a single pass, whereas sheet-fed offset carton printing requires several finishing operations away from the press and a higher labour content. It also allows the economical production of cartons in far shorter runs, albeit with more restricted formats. Users tend to be integrated packaging groups or specialised carton printers serving international pharmaceutical and tobacco industries.

Leading press manufacturers like Drent Goebel, Gallus Group, Ko-Pack International, Mark Andy/Comco, Omet and Nilpeter offer several types of multi-function film and/or carton production models.

According to Jakob Landberg, sales director of Danish-based Nilpeter, the multi-product philosophy has begun to take hold: “We recognise that our customers’ services are now less single-product driven, but instead increasingly involve a mix of different products. These in turn reflect their clients’ product branding demands.”

He sees increasing demand for advanced combination presses that combine several print processes with interchangeable print units and in-line conversion devices.

Other high-end features may include centralised controls with touchscreen panels and job data storage/retrieval. Fault detection is even more critical when running expensive materials like film or cartonboard and this is met by advanced forms of video web inspection.

Some modules will inspect both sides of the web simultaneously, while coping with reflective substrates and metallic inks. Another option is to inspect the relative position of transparent varnishes and cold-seal liquid adhesives, as used for pouches.

Underpinning the various narrow-web processes is a flourishing pre-press sector covering origination, repro and platemaking products. Major vendors of hardware and software solutions like Artwork Systems, Creo Europe, Esko-Graphics and DuPont Imaging Technologies now have dedicated sales and service divisions for the label and packaging industries.

In fact, flexo-oriented pre-press has become a dynamic business, involving the latest electronic origination systems that can work with a multitude of file input/output formats, aided by fast telecommunications links between suppliers and their customers, including remote digital proofing.

The arrival of smaller-format computer-to-plate systems using either laser or thermally-activated plate imaging systems for offset or flexo plates (or seamless sleeves) has revolutionised the platemaking scene.

Appropriately, we end with digital colour printing. All models have a digital front-end system to scan originals and create text and images on electronic media using a print engine, all without film or plates.

The digital files go directly from origination to press, which allows in-house production of very short runs with fast job turnaround times. Depending on front-end memory, it is also possible to personalise every piece of print or have variable numbering and coding.

The latest models give near-offset print quality, reliable operation and a wide choice of pressure-sensitive materials, packaging films and papers. Current roll-fed label systems include the new six-colour HP Indigo ws2000/4000, which uses a patented electro-ink and offset-type production method. The company claims a six-colour job can be set-up in under 15 minutes, with full matching of Pantone colours.

The established Nilpeter DL-3300 uses Xeikon’s photoconductive drum system using toner-based inks. Both systems are available with a selection of in-line die-cutting, varnishing and rewind facilities.

Digital colour printing has been around since 1993, but remains a long way from fulfilling its full potential in labelling and packaging. Investment and running costs have become relatively cheaper, but material costs are high compared with conventional printing processes. Filling such presses, let alone making a profit, demands a highly innovative approach to business.

Nevertheless, some converters successfully run digital presses alongside conventional presses to offer a complete short-to-long run service. The on-demand ethos offers many advantages, not least in allowing buyers to specify labels to meet regional or seasonal marketing initiatives.