A vast variety of different shapes and types of art brushes are available for painting. Each variable can have numerous effects and applications.
Waterbrush: A Cross Between a Brush and a Fountain Pen
2007 Marion Boddy-Evans
A waterbrush is like a combination of a fountain pen and a brush. It consists of a head with the brush on it and a handle that's a plastic reservoir that holds water. The two parts screw together and apart very easily. A slow, constant trickle of water comes down the brush's bristles as you use it, and you can get more by squeezing the reservoir.
A waterbrush is ideal for using with watercolor paints and watercolor pencils, including lifting color directly from them. Various manufacturers produce waterbrushes, in a few sizes, and in either a round or flat shape. If your local art store doesn't stock them, many online art stores do.
Waterbrushes are useful for on-site sketching, together with a small travel watercolor set, as it eliminates the need to take a container with water. To clean the brush, simply squeeze it gently to encourage more water to flow out, then wipe it on a tissue. It doesn't take much water to clean the brush, but it's also easy to refill the waterbrush's reservoir from a tap or a bottle of water.
Different brands work slightly differently. Some have an easier, continuous flow of water and others require a definite squeeze to get water out. It is generally not recommended to fill waterbrushes with dilute watercolor nor with calligraphy ink, since both may clog up the brush. Depends on the brand of the waterbrush (and particle size in the ink) it may be possible to fill the brush with sepia ink without problems.
A waterbrush doesn't hold as much pigment as a sable watercolor brush since the bristles as synthetic, so you'll find yourself picking up color more often. The bristles are also prone to staining (as you can see in the photo), but that's hardly unique to a waterbrush.
A waterbrush makes painting from a dark to a light color really simple: Keep painting and the extra water thins the paint until eventually all that's left is water. But these brushes also make painting large areas an even tone trickier than with a conventional brush.