The interfacial tension σsl is calculated based on the two surface tensions σs and σl and the interactions between the phases. These interactions are interpreted as the geometric mean of a disperse part σD and the corresponding acid parts σ+ and base parts σ- of the surface tension or surface free energy.
According to the Lewis acid-base theory, polar interactions take place when an electron acceptor (+) impinges on an electron donor (-). The geometric mean is accordingly formed from the respectively opposing parts.
At least three liquids are required to determine the surface free energy of the solid: a purely dispersive liquid and two liquids with known acid and base parts. As the neutral point in the Lewis scale, water should be used in all cases.
- R. J. Good; C. J. van Oss, The Modern Theory of Contact Angles and the Hydrogen bond Components of Surface Energies. In: G. I. Loeb; M. E. Schrader (Hrg.): Modern approaches to wettability. 1992, P. 1-27.
- R. J. Good, Contact Angle, Wetting and Adhesion: a Critical Review. In: K. L. Mittal (Hrg.): Contact Angle, Wettability and Adhesion. Festschrift in Honor of Professor Robert J. Good. Utrecht 1993, P. 3-36.
- C. J. van Oss; M. K. Chaudhury; R. J. Good, Interfacial Lifschitz-van der Waals and Polar Interactions in Macroscopic Systems. In: J. Chem. Rev. 88 (1988), P. 927-941.