American artist Jackson Pollock's paintings often clashed with the rules of the art world. But they couldn't defy（藐视，挑衅） the laws of physics, according to a multidisciplinary team of researchers from Boston College and Harvard who give quantitative form to Pollock's methods and genius in the latest edition of the journal Physics Today. Quantitative analysis is a phrase few would associate with Pollock, the abstract expressionist who during the 1940s and 50s adopted the method of pouring paint onto canvas（帆布） in order to convey his artistic vision in an interplay（相互影响） of drizzles（细雨） , drips and splashes.

But physicist Andrzej Herczynski and art historian Claude Cernuschi of Boston College and mathematician L. Mahadevan of Harvard brought their respective expertise together to develop a quantitative portrait of Pollock's techniques, showing Pollock as an intuitive master of laws that govern the flow of liquids under gravity.

Under a scientific lens, Pollock's drizzles, drips and splashes reveal the workings of physical phenomena known as jets, drops and sheets. Each is governed by the laws of fluid dynamics, which Pollock exploited through careful technique and manipulating the thickness of his pigments（染料） and paints with water and solvents, according to the researchers.

"When Pollock is creating his pieces, he is enlisting gravity as a participant – as a co-conspirator," said Cernuschi, a professor of art history. "He has to understand how pigment is going to behave under the laws of gravity. He has to anticipate what is going to happen and work accordingly. There is both spontaneity and control, just as there is in the improvisation of a jazz musician. In order to understand what is taking place with Pollock, it's essential to understand the laws of physics and the dynamics at play under the laws of gravity."

There has long been speculation about the role of fluid dynamics in Pollock's work, but never before an explicit（明确的，清楚的） quantitative exploration of Pollock's primary methodology – painting with jets, or continuous flows of paint – and his less frequent use of drops and perhaps sheets, said Herczynski, laboratory director and research associate professor of physics at BC.

Herczynski and Mahadevan, Harvard's Lola England de Valpine Professor of Applied Mathematics and a professor of biology and physics as well, looked at Pollock's techniques and the physical aspects of paint on canvas in order to understand the forces at play. Their calculations describe Pollock's lifting and dispensing of paint in terms of paint load volume, viscosity（粘度） , flow rates, gravity, and other factors.

Pollock worked by loading a stick or trowel with a far greater amount of paint than a brush holds during conventional easel painting. He released a jet of liquid to the canvas placed on the floor below. Pollock's physical technique – captured in still photographs and movies of the artist at work – reflect his efforts to control liquid-jet dynamics such as fluid instability called coiling, the circular motion of the tail of a thinning paint jet, similar to the way a stream of syrup "coils" on a pancake, the authors note. While Pollock may have instinctively understood how to control these forces, it would be years later before scientists came to fully understand them in theory and practice.

"By pouring paint in this continuous jet fashion or by dripping it, he incorporated physics into the process of painting itself," said Herczynski. "To the degree that he did and to the degree he varied his materials – by density or viscosity – he was experimenting in fluid dynamics, although his aim was not to describe the physics, but to produce a certain aesthetic effect."