Methods for solids:
Sessile drop, dynamic Wilhelmy, single fiber, powder contact angle.
Methods for liquids.
Static: Du Nouy, Wilhelmy Plate, spinning drop, pendant drop.
Dynamic: Bubble pressure and drop volume.
Measuring of contact angle, surface tension, interfacial tension, bubble pressure.
Sessile Drop method
Sessile drop method is a optical contact angle method. This method is used to estimate wetting properties of a localized region on a solid surface. Angle between the baseline of the drop and the tangent at the drop boundary is measured. Ideal for curved samples or where one side of the sample has different properties than the other.
Dynamic Wilhelmy method
A method for calculating average advancing and receding contact angles on solids of uniform geometry. Both sides of the solid must have the same properties. Wetting force on the solid is measured as the solid is immersed in or withdrawn from a liquid of known surface tension.
Single Fiber Wilhelmy method
Dynamic Wilhelmy method applied to single fibers to measure advancing and receding contact angles.
Powder Contact Angle method
Enables measurement of average contact angle and sorption speed for powders and other porous materials. Change of weight as a function of time is measured.
Static methods
Du Noüy Ring method
The traditional method used to measure surface or interfacial tension. Wetting properties of the surface or interface have little influence on this measuring technique. Maximum pull exerted on the ring by the surface is measured.
Wilhelmy Plate method
A universal method especially suited to check surface tension over long time intervals. A vertical plate of known perimeter is attached to a balance, and the force due to wetting is measured.
Spinning Drop method
This technique is ideal for measuring low interfacial tensions. The diameter of a drop within a heavy phase is measured while both are rotated
Pendant Drop method
Surface and interfacial tension can be measured by this technique, even at elevated temperatures and pressures. Geometry of a drop is analyzed optically.
Dynamic methods
Bubble Pressure method
A measurement technique for determining surface tension at short surface ages. Maximum pressure of each bubble is measured.
Drop Volume method
A method for determining interfacial tension as a function of interface age. Liquid of one density is pumped into a second liquid of a different density and time between drops produced is measured.
