Acrylic paints were developed in the 1940's. Twenty years later, artists like Andy Warhol and Roy Lichtenstein were using them to create famous paintings. Acrylic paints can be used thick like oil paints or thinned out and used like watercolors. Acrylic painting has traditionally been done with oil-paint brushes. Recently, manufacturers have come out with lines of brushes meant to be specifically compatible with acrylic paint. Acrylic paint is water based, which means acrylic brushes can be washed using water. However, acrylics are synthetic paints so they are hard on brushes.
Purchase brushes with synthetic bristles, usually made from nylon. Buying quality brushes ensures that they will last a long time and stand up well to the chemicals in acrylic paint. Natural bristle brushes, usually used with oil paints, will create a streaky look when used with acrylic paints. Polyester bristle brushes are also good for acrylic painting.
A long-handled brush is recommended for acrylic painting. A long handle creates more space between you and your canvas. You get a better perspective of the composition of the painting if you're at a distance. Also, your hand won't be in the way with a longer brush. Shorter brushes can be a problem, with your hand either intruding upon your line of sight or getting in the way of the light and casting shadows across your canvas. Longer brushes also give you a loose, painterly line when you hold them near the end and a sharp, draftsman style when you hold them close to the ferrule.
The material used to create bristles creates either a stiff or soft brush. Nylon brushes are soft and pliable. Polyester brushes tend to be stiffer. The best possible option is to purchase a brush that is half nylon and half polyester. These brushes have a medium level of softness but are still durable.
Different brush shapes create different lines. There is a huge variety of shapes, but you should focus on the basic brushes. An angled brush is good for painting lines and curves. Fan brushes are used to blend colors together in a way that results in a natural look. They can also be used to create different textures and effects. Filberts have an oval head; they are an all-purpose brush. Used on the side, they create a thin line; used flat they create a thick, broad stroke. Riggers are thin brushes used to paint details. They work best with thinned-out paint. Flats are good for applying thick layers because they hold a lot of paint. Short flats, or brights, produce short, crisp strokes. When dampened, their edges become sharp and chisel-like, aiding in the painting of thin, straight lines. Rounds come to a sharp point, allowing you to paint details.