The concept of the contact angle is also depicted with a small liquid droplet on a flat horizontal solid surface. The shape of the droplet is determined by the contact angle. If the liquid is very strongly attracted to the solid surface (for instance, water on strongly hydrophilic solid) the droplet will completely spread out on the solid surface with a contact angle close to 0°, in a condition of surface complete wettability.

Less hydrophilic solids will have a contact angle up to 90°. If the solid surface is hydrophobic, the contact angle will be larger than 90°. Highly hydrophobic surfaces have water contact angles as high as 150° or even nearly 180°. Water droplets simply rest on the surface, without actually wetting it to any significant extent. High hydrophobic conditions can be observed on fluorinated surfaces (Teflon-like coatings). As a rule, a high contact angle indicates a low solid surface energy or chemical affinity and a low contact angle a high solid surface energy or chemical affinity.

The sessile drop method, the most often used in the converting industry, is measured by a contact angle goniometer using an optical subsystem to capture the profile of a pure liquid on a solid substrate. The angle formed between the liquid/solid interface and the liquid/vapor interface is the contact angle. Older systems used a microscope optical system with a back light. Current-generation systems employ high resolutions cameras and software to capture and analyze the contact angle.

As part of it surface treating lab trial services, Enercon can provide contact angle measurements.