40 Dynes—But Relative to What Ink?
Ink technical data sheets commonly specify that a substrate must reach 38, 40, 42, or even 44 dyn/cm before printing.
But wetting is not determined by the substrate alone.
The liquid ink has surface tension.
The solid substrate has surface energy.
Wetting occurs at the interface between them.
Graphic 1: Two different surface properties
The first graphic illustrates an essential distinction:
Ink, as a liquid, is characterized by surface tension.
The substrate, as a solid, is characterized by surface energy.
These are different properties, but printability depends on how they interact.
This raises an interesting technical question:
If both values influence wetting, why do most ink technical data sheets publish the required dyne level of the substrate—but rarely disclose the surface tension of the ink?
One practical explanation is that the ink manufacturer controls the formulation, including resins, solvents, monomers, surfactants, pigments, and wetting additives.
The printer, however, controls the condition of the substrate:
- Treatment level
- Surface contamination
- Additive migration
- Storage and handling
- Treatment decay
- Time between treatment and printing
For that reason, the technical data sheet normally communicates the variable that the printer can verify directly: the minimum surface energy required from the substrate.
But this does not make the ink’s surface tension unimportant.
It simply means that one side of the interface is published, while the other often remains an internal formulation and quality-control parameter.
Graphic 2: What the dyne test shows
The second graphic illustrates the practical principle behind dyne testing.
When the selected test fluid does not wet the surface adequately, the applied line retracts and breaks into droplets.
When the fluid remains as a continuous film for the specified observation period—commonly around three seconds—the surface is considered to have reached at least the corresponding test level.
The result provides useful information about the condition of the substrate surface.
However, a passing dyne test does not directly measure:
- The surface tension of the production ink
- Static versus dynamic ink behavior
- Chemical compatibility between ink and substrate
- Final adhesion after drying or UV curing
- Resistance to abrasion, chemicals, or delamination
It confirms one important part of the system—but not the entire printing process.
A substrate can meet the published dyne requirement and still experience poor results because of ink modification, contamination, incompatible additives, dynamic wetting behavior, curing conditions, or differences in surface chemistry.
That is why a dyne value should not be interpreted as an absolute guarantee of printability.
A dyne level describes the condition of the substrate. The final result depends on both sides of the interface.
Good printability starts with good wetting.
The test is simple. The interface is not.
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