The contact angle?

What is the contact angle?

The contact angle (also known as the wettingangle) is the angle formed between a drop of liquid on the surface of a solid material to that surface. The size of the contact angle between the liquid and solid material depends on the interaction between the materials on the contact surface.
The smaller this interaction, the larger the contact angle will be. By identifying the contact angle, certain properties of the surface, (eg. surface energy) can be determined. The larger the contact angle, the more difficult it is to wet the solid material and the less foreign bodies are able to adhere to the surface.