Why Automated Viscosity Control is Important for Your Application

If you’re a manufacturer in the flexographic printing or industrial coating industry, monitoring and controlling the ink and coating viscosity is critical for your finished product. Not automating viscosity control could eventually cause a host of otherwise preventable issues — issues that can seriously compromise the quality of your product.

As the saying goes, “Better to have it and not need it, than to need it and not have it.”

First, a review: Understanding Ink Viscosity in Printing and Coating Processes

As a quick reminder, viscosity refers to a fluid’s resistance to flow — a key parameter in the printing and coating industries. In simple terms, a high-viscosity fluid (or “thicker” fluid) flows more slowly than a low-viscosity fluid (or “thinner” fluid). For example, think of the difference in flow rate between printing ink and water at room temperature. Understanding and controlling fluid viscosity is crucial for precision ink transfer, uniform coating application, and achieving consistent results in flexographic printing and gravure processes.

Knowing the flow rate or viscosity of your process fluid is important for several reasons, not least of which is quality control. As previously mentioned, poor viscosity control can result in a variety of quality issues.

As previously discussed, the Zahn cup is a type of efflux (flow) cup viscometer used to spot check, not control the process fluid viscosity.

Other types include:

• Orifice viscometers
• Capillary (U-tube) viscometers
• Consistometers

Efflux (flow) cup viscometers tend to be the most popular with manufacturers — especially in the printing industry — thanks to their low cost, simple usage, and minimal maintenance requirements. 

Why Are Process Viscometers Useful?

This is where automated process viscometers come into play. These in-line viscosity measurement systems, when integrated with a real-time viscosity control system (which we’ll explore in future posts), help maintain fluid viscosity within tight tolerances—ensuring consistent ink flow, uniform coating application, and overall process stability.

Industrial process ink viscometers encompass a range of devices designed specifically to measure and control fluid viscosity during production. From rotational viscometers to vibrational and torsional systems, each technology approaches viscosity monitoring differently, but all share the same goal: maintaining optimal viscosity levels for reliable, repeatable results in flexographic printing, gravure coating, and other high-performance manufacturing environments.

Example of Process Viscometers

• Falling piston and ball viscometers
• Rotational viscometers
• Torsional viscometers
• Vibrational viscometers

Each of these viscometer technologies uses a different principle of operation to measure process fluid viscosity. For example, falling piston, falling ball, and rotational viscometers are mechanical viscosity sensors that operate by creating shear between a moving and a stationary surface in contact with the process fluid. Often installed offline in an ink reservoir or coating tank, these viscometers require regular maintenance, manual cleaning, and periodic replacement of wear parts due to direct fluid contact. While widely used, these systems can be prone to downtime and inconsistent readings, making them less ideal for real-time, in-line viscosity monitoring in high-speed flexographic or gravure printing environments.

Vibrational or torsional viscometers measure viscosity by detecting the dampening effect on an oscillating electromechanical resonator immersed in the fluid. These advanced in-line viscosity sensors deliver continuous, real-time viscosity readings, ensuring consistent ink or coating performance throughout the production run. Installed directly in the process line—between the ink or coating tank and the application head or chamber system—they offer several advantages: no moving parts, minimal maintenance, and no need for manual removal or cleaning. Cleaning is handled automatically via a reverse flush or auto wash system, typically integrated into the printing press or coating line, making these sensors ideal for high-speed, closed-loop viscosity control in flexographic, gravure, and industrial coating applications.

Measuring and Maintaining Your Ink Viscosity

As mentioned earlier, failing to measure and maintain process fluid viscosity can lead to a wide range of production issues. Variations in viscosity—whether the fluid becomes too thin or too thick—can significantly impact how your printing or coating equipment handles the material. Without consistent viscosity control, you may encounter common problems such as:

• Inconsistent color
• Ink consumption
• Anilox plugging
• Dirty printing plates
• Ink slinging
• Press down time for cleaning issues
• Job rejections

Implementing real-time viscosity monitoring helps prevent these issues, ensuring stable fluid behavior, optimized machine performance, and high-quality output in demanding flexographic, gravure, or industrial coating environments.

Once you begin to use an automated viscometer and control system to regularly maintain the viscosity of your process fluids, you may find:

• More consistent color or coating weight 
• less cleaning issues
• fewer rejections 
• more prints impressions per volume of ink

All of which reduces operational costs, increasing your bottom line.

Conclusion 

Consistent viscosity control is key to maintaining quality, reducing waste, and improving efficiency in flexographic printing and industrial coating. Automated in-line viscometers help ensure precise, real-time monitoring—minimizing downtime and maximizing output. Investing in the right viscosity control system means better results, fewer issues, and a stronger bottom line.

For more information, please contact INKSPEC.  Sales@inkspec.com  +14504415005  www.inkspec.com