Understanding how liquids interact with solid surfaces—known as surface wettability—is crucial in industries ranging from electronics and coatings to medical devices and packaging. Two of the most common techniques to assess wettability and surface energy are contact angle measurements and dyne pen testing. But how do these methods compare, and why do we believe you should replace the dyne pens with contact angle measurements?
Comparison of techniques
Contact angle measurement is a quantitative technique that evaluates the angle a liquid droplet forms at the interface with a solid surface. This angle reflects the degree of wettability:
• Low contact angle = high wettability (the liquid spreads out)
• High contact angle = low wettability (the liquid beads up)
The measurement is typically performed using an optical tensiometer, which provides accurate and repeatable results. Contact angle measurements can be performed in various ways, including static, advancing, and receding angles, to provide more detailed information about the surface.
Dyne pen testing is a quick and simple qualitative method for estimating the surface energy of materials, particularly plastics and films. Dyne pens are felt-tipped markers filled with liquids of known surface tension (measured in dynes/cm). By drawing a line on the surface, you observe whether the liquid beads up or spreads out:
• If the liquid spreads and remains continuous for 2 seconds, the surface energy is higher than the pen’s value.
• If the liquid beads up or breaks apart, the surface energy is lower than the pen’s value.
While dyne pens offer a fast and relatively easy method for testing, the results are qualitative, operator-dependent, and subjective. Furthermore, the results cannot be stored for quality control purposes. In addition, the use of dyne pens is limited to certain types of surfaces.
Contact angle measurements offer a means to evaluate the surface quantitatively. Measurement is performed with the optical tensiometer, which provides an automated measurement that is not dependent on the user. The results can be readily stored. Contact angle measurement can be performed on a wide range of surfaces, including very hydrophilic or hydrophobic materials.
| Feature |
Contact angle measurement |
Dyne pen testing |
| Data type |
Quantitative (angle, energy) |
Qualitative / Threshold |
| Precision |
High |
Low |
| Surface suitability |
Broad (metals, glass, polymers) |
Best for smooth, non-porous |
| Operator dependency |
Low (automation possible) |
High (subjective) |
| Speed |
Moderate (seconds/minutes) |
Fast (seconds) |
| Cost of operation |
One-time instrument purchase price |
Dyne pen renewal price |
| Advanced information |
Yes (surface roughness, heterogeneity, dynamic effects) |
No |
Steps to replace dyne pen with the contact angle
When contact angle is used to replace dyne pens, the most common approach is to measure contact angle with water. Water contact angle alone can estimate the surface free energy value
• Low water contact angle = high SFE energy
• High water contact angle = low surface free energy
A calibration curve can be done to find a water contact angle value that correlates with the required surface properties. However, if the measurement of surface free energy is needed, it can be easily done with the same instrument.
Conclusion
Both contact angle and dyne pen methods have their place in surface science and quality control. Choosing the right method depends on your needs for precision, speed, and context of use. For the most accurate and insightful results, especially in high-value applications, contact angle measurement is the gold standard.
