  Painting is a fluid mechanical process. The action of covering a solid
surface with a layer of a viscous fluid is one of the most common human
activities; virtually all man-made surfaces are painted to provide protection
against the environment or simply for decoration. This process, in an
industrial context, has been vastly studied and it is well understood. In case
of artistic painting the purpose is different. Painters learn how to manipulate
the non-uniform deposition of paint onto a surface, through lengthy empirical
testing of the action and modifying the physical properties of the fluids, to
create textures and patterns of aesthetic value. In this paper, an analysis of
some notable painting techniques is presented from the point of view of fluid
mechanics. In particular, we discuss the so-called `accidental painting'
technique, originally devised by David A. Siqueiros, which is the result of a
Rayleigh-Taylor instability. An analysis of several techniques used by Jackson
Pollock is also presented, showing how he learned to carefully control the
motion of viscous filaments to create his famous abstract compositions. We also
briefly discuss how pattern and textures are produced in decalcomania and
watercolor painting. These investigations indicate that it is possible to
establish concrete scientific discussions among modern fluid mechanics, art,
art history and conservation.
