of a fluid to spread
readily and uniformly over the surface of another fluid or solid, forming a thin, continuous film
. Fluids with high
surface tension (such as mercury) have little or no wetting ability; those with low surface tension (such as petroleum
solvents) have high wetting ability. Fluids with medium surface tension (such as water) acquire greater wetting ability with the addition
of a wetting agent
. Wetting ability is of critical importance in cleaning, dyeing, painting, and printing.