Surface Tensiometers
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Measurement of the surface tension of liquids
Surface tension is a property of liquids that causes them to minimize their surface area to the smallest possible value, which would result in a perfectly spherical shape under zero gravity. Measuring surface tension allows characterizing properties such as wettability, permeability, solubility, foamability, emulsifiability, dispersibility, etc. The different methods to determine the surface tension are as follows:
Wilhelmy Plate Method
A balance system measures the force
of the liquid pulling on the plate
Du Noüy Ring Method
A balance system measures the force
of the liquid pulling on the ring
Pendant Drop Methods
A software analyzes a digital image of
a droplet suspended from a needle tip
Bubble Pressure Method
Determination of the maximum internal pressure of
an air bubble formed in a probe immersed in a liquid
Dynamic Surface Tension
Surfactants can lower surface or interfacial tension over time by being absorbed at the newly formed surface or interface. During the time from the creation of a new surface to the attainment of equilibrium surface tension, dynamic surface tension can be measured; at the liquid's equilibrium state, static surface tension can be measured. Detergents and coating solutions are used in processes where new surfaces or interfaces are constantly being created; thus, determining the Dynamic Surface Tension is of high importance.