Viscosity is the thickness of a liquid. Low-viscosity liquids are very fluid (such as water) while high-viscosity liquids are quite thick (such as molasses). The viscosity of oil paints is usually reduced by adding binder (such as linseed oil) and/or solvent (such as turpentine). At a lower viscosity, paint can be brushed onto the canvas more freely and quickly.

Abstract Expressionist New York
The Museum of Modern Art, October 3, 2010–April 11, 2011
MoMA.org/abexny
Filmed by Plowshares Media
© 2010 The Museum of Modern Art