Paintbrush
A paintbrush is a brush used to apply paint or sometimes ink. A paintbrush is usually made by clamping the bristles to a handle with a ferrule.
Decorators' brushes
The sizes of brushes used for painting and decorating are given in millimeters (mm) or inches (in), which refers to the width of the head.
Common sizes are:
Metric: 10 mm, 20 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm.
Customary: 1⁄8 in,1⁄4 in, 3⁄8 in, 1⁄2in, 5⁄8 in, 3⁄4 in, 7⁄8 in, 1 in, 1 1⁄4 in, 1 1⁄2 in, 2 in, 2 1⁄2 in, 3 in, 3 1⁄2 in, 4 in.
Bristles
Bristles may be natural or synthetic. If the filaments are synthetic, they may be made of polyester, nylon or a blend of nylon and polyester.
Filaments can be hollow or solid and can be tapered or untapered. Brushes with tapered filaments give a smoother finish.
Synthetic filaments last longer than natural bristles. Natural bristles are preferred for oil-based paints and varnishes, while synthetic brushes are better for water-based paints as the bristles do not expand when wetted.