Actions:

#01a. Calibration of the bubble tensiometer…
#01b. …and surface tension check of the water sample
#02. Mounting the cleaned capillary
#03. Preparation of the test sample
#04. Insertion of the capillary and temperature probe
#05. Start of the measurement
#06. Bubble generation (average duration: 20 minutes)
#07. Data acquisition
#08. Post-analysis capillary cleaning

The surface tension of a fluid is typically measured using bubble pressure tensiometers, which determine the pressure required to form an air bubble at the tip of a thin tube immersed in the liquid.
The process begins with the calibration of the instrument, aligning it with a known reference—typically tap water, which has a surface tension of approximately 72 mN/m.
This reference enables consistent, repeatable procedures when measuring other fluids.

The tensiometer is equipped with a capillary tube that, once submerged, blows air at a set frequency, generating a series of bubbles of defined size.
Each bubble is subject to the resistance of the surrounding fluid. The surface tension is determined based on the interfacial free energy between the bubble and the fluid, as well as the surface area of the bubble itself.

The key measurement is the maximum internal pressure of the bubble, tracked over its lifetime at the interface. The result is a graph displaying:
1. A curved line, indicating the surface tension behavior of the test fluid
2. A horizontal line, representing constant temperature