Advancing and Receding Contact Angles: Wetting History Can Change the Result

Define the Interface or Transport Basis

KRÜSS describes contact-angle hysteresis as the difference between advancing and receding observations. Real surfaces can display this behavior through roughness or chemical variation. State which liquid phase contains the angle and whether the contact line advances, recedes or remains pinned.

Review a Hypothetical Comparison

For an invented surface and liquid, a controlled advancing test gives 96 degrees and a receding test gives 62 degrees. The observed hysteresis is 34 degrees. Comparing another surface's receding value of 68 degrees against the first surface's advancing value would answer no consistent wetting question. An intermediate static drop reading is a separate observation, not an automatic replacement for either moving-boundary result.

Keep the Evidence with the Decision

Draw the contact-line direction next to each recorded angle. Keep the surface preparation, liquid addition or withdrawal history and observation location with the result. If a coating review concerns a moving liquid front, request the direction relevant to that front. If it concerns retained drops, keep both moving-boundary observations and the actual retention behavior.

This worksheet preserves the measurement history; it does not translate hysteresis into a universal cleaning or adhesion score. A change after surface treatment still needs repeat observations under the same preparation and motion conditions.

Which direction of contact-line motion belongs to the stated wetting observation?

This blank worksheet is for your own project. It contains no H M machine trial result.

Customer Questions

Primary References

These references support the technical principles discussed in this guide. The worked examples and review questions are educational.

• KRÜSS describes contact-angle hysteresis
• Reference from hmpharmamachines.com