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Essential Flexographic Ink Tests for Quality Printing

Flexography, a versatile printing process, relies on specialized inks to achieve high-quality results.

Unlike traditional letterpress printing, which uses slow-drying inks, flexography employs fast-drying inks with unique properties.

In this article, we'll explore the critical differences between flexo inks and letterpress inks, and discuss six essential tests that every flexographer should be familiar with to ensure consistent printing performance.

Ink TestingInk Color and Strength

One of the primary concerns in flexography is ink color and strength.
The color and strength of an ink can significantly impact the final printed product.
To assess this, pressmen perform drawdown tests on a fine-grain bleached paper stock.
The initial part of the drawdown simulates the solid print that will be achieved on the press, while the lighter portion reveals undertones and shade differences.

Drying Time

The drying time of flexographic inks is crucial for efficient printing.
Alcohol-reducible inks are tested by making heavy rollouts on a non-absorptive surface.
Pressmen tap the ink films to determine when they reach a tack-free state.
Water-reducible inks, on the other hand, rely more on penetration than evaporation for drying.
A drawdown test on the actual substrate helps assess drying rates.

Solids Content

The solids content of ink plays a vital role in print quality.
A precise method to determine solids content involves evaporating a sample to dryness and weighing the residual material.
This information aids pressmen in adjusting ink formulations as needed for optimal results.

Fineness of Grind

For flexographic inks used in critical color process work or for achieving a smooth, glossy surface, fineness of grind is crucial.
Specialized tools like grind gauges provide precise measurements.
A rough estimate can also be made by smearing ink on a smooth glass plate.

Weight per Gallon

The weight per gallon of an ink is an important parameter to know.
Standard cups are used for measurement, and the weight in grams is divided by 10 to obtain the weight per gallon in pounds.
This information can be used to calculate specific gravity, a vital factor in ink formulation.


Viscosity is a fundamental property for flexographic inks.
Rotational laboratory instruments provide precise measurements, but pressmen often rely on efflux cups like Zahn, Shell, and Ford cups.
Viscosity measurements are recorded with the cup type and temperature to ensure consistency.

Conclusion In the world of flexographic printing, understanding and testing ink properties are essential for achieving consistent and high-quality results.

By performing these six simple tests, pressmen can ensure uniformity of performance and printing results, avoid costly mistakes, and maintain control over the ink composition.

As the demands of flexographic printing evolve, incorporating these tests into standard practices becomes increasingly important to meet the challenges of complex substrates and color-process jobs.