The contact angle θ has achieved significance as a measure of wettability.
As shown in Figure 4-1, as the contact angle decreases, the wetting characteristics of the liquid increase.
Complete wettability would be evidenced by a zero contact angle, and complete nonwetting would be evidenced by a contact angle of 180°.
There have been various definitions of intermediate wettability but, in much of the published literature, contact angles of 60° to 90° will tend to repel the liquid.