Accurate, repeatable color—every printer strives for it.
To succeed in achieving the ever-present goal requires recognition and control of a considerable number of variables. When problems like dirty print, misting, bridging, feathering, hickeys and more arise, one popular refrain starts to sound: “It’s always the ink’s fault!” Truth be told, such a claim is far from correct.
Given that solubility, stability, pigments, resins, additives, adhesives, density, screen values—even sustainability—impact laydown and hence, delivery of good quality print. But so do the ink’s relationships with other critical components of the package printing process, namely: the press itself, as well as the speed it runs at; the plate, substrate, anilox and doctor blade. Credit faults occurring in these relationships with resulting in lifting, spitting, surface energy transfer and more.
Getting ink to press—economically, effectively and efficiently—is argumentatively and uncompromisingly one of the single most important processes in meeting color expectations and matching proof to press.
That said, FLEXO Magazine recently put a short list of questions out to a number of different major ink manufacturers, with three electing to offer submissions. Specifically, we asked:
- What are a printer’s five most pressing challenges related to ink on press?
- Discuss how and why the problem develops/persists, and offer hints at what measures can be taken to address it
- Speak to your company’s solution: What is it? How and why does it work? What benefits can a printer derive from its use?
Expert commentary offered by executives at Sun Chemical Corp, Wikoff Color Corp and Zeller+Gmelin hones in on formulating a specific ink for a given application. In effect, what’s said serves as a guide to process control, while at the same time addressing a step-by-step approach to troubleshooting.
What amounts to this executive roundtable involves Jim Felsberg, field marketing manager and Moe Rahmeh, technical customer service functional excellence director, Sun Chemical Corp; Wikoff Color Corp label experts, led by Mark Lewis, label market manager; and Ed Dedman, flexo technical support product manager, Zeller+Gmelin. The presentation is organized into three separate sections, each under its own heading.
Variables Dictate Success
Ink must be designed to work with the press, anilox roller, substrate and plates, according to Sun Chemical Corp executives Jim Felsberg and Moe Rahmeh. These flexographers emphatically state: “At the design stage, it is easier to select solvents and resins that can optimize the solubility of the ink, while ensuring all critical properties are achieved.”
They report, “To ensure our customers generate the best quality print, Sun Chemical offers an Ink Troubleshooting Guide that highlights a range of common on-press challenges. Users can search by printing process to review specific problems and general solutions, which allows them to troubleshoot issues backed by our team’s knowledge and expertise.”
To the questions at hand, the duo lists five prominent ink-related everyday challenges:
- Anilox volume vs. ink drying speed
- Consistent color development
- Press speed vs. ink drying speed
- Solubility and stability
- Plate/ink interaction
Felsberg begins the analysis this way. “Challenge No. 1—anilox volume versus ink drying speed—comes down to this fact. How deep the engraving is on a ceramic anilox roller impacts how much ink is applied in the printing process.” He explains, “This mechanical process inevitably develops wear over time, presenting an issue for printers that requires regular maintenance to ensure the anilox volume is still applying the correct amount of ink.”
Elaborating on the point, he states, “When the anilox rollers wear, or the cell volume decreases, the inks need to change not just for color strength, but also drying speed. Sun Chemical suggests that a difference of 15 percent or greater from the original volume will create the demand for a revised ink formulation.”
“At the design stage, it is easier to select solvents and resins that can optimize the solubility of the ink, while ensuring all critical properties are achieved.”
Felsberg indicates, “The main reason for this standard is that inks are designed for a specific anilox volume, and when the anilox doesn’t match that formulation, the color and/or drying speed will be affected. For example, if a printer has specified an anilox with a volume of 2.5 bcm but is running an anilox with a volume of 1.8 bcm, the production team may attempt to tone the ink to keep the color consistent. This can cause ink consistency issues during the pressrun, and in some cases, the critical qualities and properties of the inks are affected.
“As a global ink supplier, Sun Chemical is well-equipped to manage these issues by asking key questions at the beginning of the ink development process,” Felsberg adds, instructing printers to ask:
- How deep are the anilox volumes?
- What is the color target?
“By pairing this in-depth background information with an inspection of the anilox rollers, our team recommends an ink composition at the outset to ensure consistency throughout the process,” he pledges.
Next, Rahmeh points to Challenge No. 2—consistent color development—and says, “Maintaining color consistency is another significant issue tied to anilox volume in flexographic printing. Specifically, when a printer uses an anilox with a standard volume of 2.5 bcm, there are rarely issues in consistent color development. However, as the actual anilox volume deviates from the standard, problems can occur that can be corrected through viscosity adjustments, while severe cases may require an ink reformulation.”
He immediately notes, “Color consistency can be affected by viscosity and temperature, while solvent evaporation can be controlled by press settings. This will reduce the number of solvent replenishments and will reduce the variables of color control. Since anilox volume dictates the color density, most colors are matched to the anilox and volume of the anilox. If the wrong anilox and/or volume are used, then color variation will begin at the beginning of the job and can cause quality problems if the inkroom does not re-match and re-tone the ink before it is added to the press.”