Surface tension and wettability instruments determine fluid surface tension, a tangential force that keeps a fluid together at the air/fluid interface. Surface tension, a measure of the quality of a chemical or formulation, can be measured according to the Du Nouy ring method or the Wilhelmy Plate method. The Du Nouy ring method measures the maximum pull that a surface applies to a ring. The Wilhelmy Plate method is used to check surface tension over long time intervals. With the Wilhelmy Plate  method, a vertical plate is attached to the balance and the force generated due to wetting of the plate is measured.

 

Surface tension measuring instruments include tensiometers, devices that are used to measure the moisture content in the soil. In some cases, a tensiometers or surface tension meter is used to schedule crop irrigation by measuring the amount of water in a field. A digital tensiometer is a surface tension measuring instrument can also be used for educational and industrial applications. A digital tensiometer is easy to use and provides accurate and cost effective surface tension measurements. Other surface tension measuring instruments are also available.

Specifications and Operating Principle

Surface tension measuring instruments differ in terms of specifications and operating principle. With some devices, surface tension is measured via the maximum differential bubble method. First, surfactant molecules called micelles are dispersed in the fluid to be tested. Two or more tubes with different orifices are then immersed in the test fluid. Finally, the difference in maximum bubble pressures is calculated to measure the surface tension. Tensiometers vary widely in terms of measurement range and resolution. A digital tensiometer displays large values for improved readability. Vessel size diameter for tensiometers can be either 50 mm or 70 mm in diameter. Specialized or proprietary surface tension measuring instruments may carry additional specifications or provide additional features.

Applications

Surface tension measuring instruments are designed and manufactured to meet many industry requirements. They are used in a variety of applications. Some surface tension measuring instruments are used in the pharmaceuticals industry, paints and coating, and cosmetics. Others are also used in emulsions, paper, films, and soap detergents. Surface tension measuring instruments should adhere to International Standards Organization (ISO) standards.