Label Printing Color Quality Control: Shanghai Fancai Highlights Five Critical Areas

In label printing, accurate color reproduction is a major factor in judging product quality. Label work also tends to involve a broad range of spot colors and many different substrates. Common ways to assess color today include visual inspection by the human eye (subjective), upper/lower limit judgment (subjective), and spectrophotometer tolerance evaluation (data).

Built on years of experience in color measurement and color management, and informed by actual production conditions at several label printing companies, here are the areas that deserve particular attention in label printing color quality control:

1. Set clear color standards and upper/lower limits—meaning the product color standard and tolerance. Before producing a given label job, define the upper limit, standard and lower limit, and retain the customer-approved master sample under seal. Over time, however, a sealed sample can shift in color. That is why an x-rite spectrophotometer and related quality control software should be used to store standard measurement data and tolerance data under common measurement conditions. Operators and QC staff can then produce and inspect according to those standards and tolerances. This supports label color consistency while allowing a practical production window, making the process workable.
2. Control color consistency in prepress and plate-making. For jobs that must match a customer sample, the dot size and density on the plate cannot be exactly the same as the supplied sample, which can lead to color differences during reproduction. Therefore, while keeping prepress electronic data consistent, plate dot data must also remain consistent—especially in flexographic and gravure printing. Each plate should be measured for screen ruling, screen angle, density and related data. For flexographic labels, the FAG flexo plate measuring instrument can be used for 3D evaluation and measurement of plate data. For letterpress and offset label printing, the x-riteicplate2XT plate inspection instrument can be selected to measure plate data. This helps ensure consistent color quality control across repeat orders.
3. A standard light source environment matters greatly to color quality control. At present, many label printing companies do not use standard lighting sources, which creates hidden risks for controlling color consistency in label prints. Many printers run two or three shifts; under their lighting, the colors seen on day and night shifts can differ substantially from those seen in daylight, leading to printing color differences. Label printers are therefore advised to install a standard light booth or standard light source viewing table where conditions permit, so employees can compare colors in a unified viewing environment. This can effectively prevent label print color differences caused by lighting issues.
4. Consistency control for spot color inks. Label printing uses many spot colors, and spot inks mixed according to Pantone color card proportions are not accurate enough; in practice, the ink system used often shows obvious color deviation from Pantone base inks. Some factories do not use a Pantone base ink system at all. Given current color matching technology and real production applications, using a computer color matching system—combined appropriately with the experience of color matching staff—can make spot color ink matching faster, more accurate and more controllable. Such a system also enables users to store and manage a large database of spot color ink formulas conveniently, making retrieval and use easier when needed.
5. In flexographic label printing, the anilox roller’s screen ruling, screen type and cell depth affect label color consistency. More and more labels are now printed by flexography. Sometimes, when matching a customer-supplied sample color, even if the prepress files, plates and spot color inks remain the same as before, the label’s spot color hue can still differ. This may be caused by anilox roller wear. Generally, in flexographic printing, the screen ruling ratio of the anilox roller to the printing plate is 3:1 or 4:1. So when flexo printing labels, besides checking the plate’s screen ruling and dots, also check the anilox roller’s screen ruling, screen type and cell depth. In particular, process differences between metal anilox rollers and ceramic anilox rollers can also cause color differences in label printing.

For the key points above that affect color reproduction in label printing, Shanghai Fancai has already delivered mature solutions to some companies in the industry. These solutions have played a positive role in helping label printers improve the operability of color control, reduce cost waste and raise production efficiency, and have gained recognition from a group of label printing companies represented by Zhengwei.

As science and technology advance, printed labels will move toward environmental friendliness, personalization, functionality and scale. Digital printing innovation will surely lead the future of label printing. Digital printing offers several major advantages: a simpler process, saved plate-making time, on-demand printing, reduced inventory, variable data, clear personalization, suitability for short runs, effective reduction of short-run printing costs, and better assurance of high-quality label printing.

—This article is reprinted from China Packaging Network (pack.cn). Original link: http://news.pack.cn/show-361787.html