Jackson Pollock made *No. 5, 1948* in the wooden barn beside his house on Long Island — on a fibreboard of about 244 × 122 cm spread on the floor. He used no brush: he poured the oil paint from a can with sticks and house-painter's brushes, straight from the tube, sometimes dripping it, sometimes flinging it. He painted moving his body in circles around the board, walking, almost dancing.

This way of working was making something not in a new style but of a new kind. Before Pollock, painting had always been done on a vertical plane; to paint on the horizontal — with gravity pressing straight onto the surface — removed representation entirely. What remained was the paint's own law: viscosity, speed, the angle of fall. Pollock said, 'I have no image in my head; I am waiting for the painting to tell me what it wants to say.'

The critic Harold Rosenberg gave this process the name 'action painting' in 1952: the painting is not a finished object but a record of an action. Clement Greenberg offered a different reading: by refusing the figurative entirely, Pollock pushed painting to the limit of its 'flatness' — the entire surface as a single optical field.

No. 5, 1948 is oil on fibreboard — a dense web of dark brown, yellow, white, and black layers overlapping. The title is deliberately empty: 'No. 5'. Pollock refused poetic or figurative titles; the viewer should stop trying to guess 'what does it want to show' and enter the visual experience directly.

The work's sale history also became a record: in November 2006 David Geffen transferred ownership of the painting through Sotheby's to the Mexican collector David Martinez for $140 million — at the time the highest known private sale price for any single painting. That figure marks how Abstract Expressionist works, which entered the market late, came to sit at the centre of the 21st century's speculative economy.