Contact angle measurement characterizes the surface energy of a solid surface.

EAG Laboratories performs optical contact angle measurements and drop shape analysis using a Dataphysics OCA25 instrument. The main application of contact angle measurement is determination of the wetting behavior of a solid surface with a specific liquid. Water drops are used to measure hydrophobicity or hydrophilicity. With individual drops of 2, 3 or more different liquids, the free energy of a surface can be calculated. A common method of surface free energy calculation is the OWRK model, which splits free energy in two contributions: a polar and a dispersive component.

In another application on the same instrument, the surface tension of unknown liquids in air (or in other media) can be measured by analysis of the shape of pendant drops, elongated by gravity.