Mary Heilmann, “Rio Nido” (1987)
The amount of paint that must have been used in order to get the drippings down the face.  The use of white space creates a helpful physical barrier as the colors transition.  The subject of this piece appears to be the crossing over of colors, rigid barriers, and a penetrable empty space.

Pirate (Untitled II). 1981.
Oil on canvas. 88 x 76 3/4".
The Museum of Modern Art, New York. Sidney and Harriet Janis Collection Fund.
©1997 Willem de Kooning Revocable Trust/
Artists Rights Society (ARS), New York.

This piece seems to have been painted from different angles.  The use of different styles, and line densities and textures makes for a piece that brings the eye in and out of the middle in several different ways.