Good packaging design on paperboard begins at the design stage. It is the graphic designer in partnership with the marketing team and a variety of packaging technologists and other partners that put shape, colour and graphics into context. Success, make or break, is often down to the converter.
A good design is one that takes into account the pros and cons of the print process and the characteristics of the substrate, and the feasibility of subsequent converting processes. A good design is one that enables print to be undertaken at a commercially viable speed while maintaining optimum colour saturation throughout the tonal range.
Paperboard and corrugated deliver in many ways
Paperboard carton and corrugated can deliver in so many ways: paperboard can be cut, creased, folded, interlocked, glued and shaped to meet an almost unending range of structurally sound formats. From a manufacturing perspective, the challenges associated with printing on a combined substrate, most notably in corrugating and boxboard, have been generally addressed by the development of boxboard structures offering more accommodating and smaller, finer fluting, such as E-flute followed by F-flute, G and N, etc.
From the design, the print, and the converting perspective smaller flutes such as ‘E” are ideal for lightweight retail cartons as they offer good printability and good bill boarding and design possibilities. For heavier, more rigid cartons, double-walled combined flutes such as “EB or “BC” are available, which allow for a good degree of creative expression and print quality.
Once known as aniline printing, flexography used to be synonymous with the printing of the brown box. Although flexo is no longer the Cinderella print process, flexography or flexo in combination with complementary converting components and processes is economically and quality viable for printing paper, boxboard/corrugated goods. But make no mistake, the direct printing, for example, onto some paperboard grades can be demanding.
Very small, very sharp dots of ink
In some situations, in order to process print to a high standard using water-based inks, it is necessary to print very small, very sharp dots of ink. This is possible if the ink thickness printed on the material is much reduced. While this is possible, the downside to reducing ink film thickness is a reduction in colour strength. For this reason, printers producing quality graphics demand highly pigmented inks and then print them at very low film weights.
There are several problems with using low film weight inks to minimise dot gain. To begin with, if the paper or the board is rough, then there may be insufficient ink coverage when using low-weight inks. This means that a compromise must be reached between dot gain and paper quality. Also, if the ink formulator raises the pigmentation level of the ink too much, there will be insufficient resin in the ink to bind the pigment to the paper surface, which also leads to a reduction in rub resistance.
The amount of ink printed onto the material is also dependent on ink viscosity, which is often arrived at by way of consultation and experimentation via the ink supplier and other supply chain providers. Once a decision has been settled upon, the converter must strive to maintain determined viscosity levels, as variations in this area will result in changes in colour strength and print quality. Factors such as heat and other variables may reduce viscosity by breaking down the small amount of thixotropic chemistry that may be present in some inks.
Faster-drying inks
Ink manufacturers must produce faster-drying inks for today’s faster runs, without compromising on re-solubility and wash-up. As the surface of the box is covered with more and more graphics, the coefficient of friction or slip of the ink becomes more important. The addition of varnishes and other coatings to improve scratch, scuff, and rub resistance can result in problems when stacking.
Colour helps to build brand image; inconsistencies, for example, in the colour of the logo negatively impact a consumer’s perception of the brand. Poor rub resistance, print and coating voids, mottling and other blemishes and faults mar presentation. Cartons, particularly for expensive goods such as cosmetics and collectables, are particularly vulnerable in that the goods may be judged now and well into the future.
In order to control process variables as much as possible, printers/converters, ink and coating and substrate manufacturers and many others use a variety of means to monitor quality and optimise the varied processes.
Sample preparation systems or colour communication proofing devices, such as the K Printing Proofer; K303S Multicoater and the FlexiProof 100, FlexiProof UV and FlexiProof LED UV, help resolve potential on-press print/coat-related issues such as colour matching off-press before they become costly on-press disasters.
In addition to colour matching capability, printability issues such as gloss, durability, flexibility, chemical resistance, scuff, etc., can be determined using a FlexiProof. All members throughout the print and converting supply chain can use the appropriate FlexiProof so as to provide identical, reproducible results that may be documented, which can be particularly useful when bringing a new product to market.
Written by Tom Kerchiss, Chairman of RK Print Coat Instruments Ltd.