Helen Frankenthaler, 1952. The 'soak-stain' technique that catalysed Color Field. National Gallery of Art, Washington.
From Wikipedia
Mountains and Sea is a 1952 painting by American abstract expressionist painter Helen Frankenthaler. Painted when Frankenthaler was 23 years old, it was her first professionally exhibited work. Though initially panned by critics, Mountains and Sea later became her most influential and best known canvas.