The mechanics of brush caligraphy

A brush is the most widely used instrument for artistic painting and calligraphy. The brush is a collection of bristles bundled together at the tip of the instrument. The bristles, which can be natural or synthetic and vary in diameter and length, hold paint or ink without dripping due to capillary forces. When artists push and move a loaded brush against a canvas or surface, the ink is released at a controlled rate to form traces use to create images and textures. We investigate the relationship among bristle bundle properties (size, packing, and wettability), fluid properties (viscosity and surface tension), and the painting action (speed and distance to the surface). We conduct controlled laboratory experiments to document and understand the process. The amount of released paint and its texture on the surface are quantified under various conditions. The measurements are compared with the predictions of a model for the ink release rate.