The brush hair and handle are held in place by the ferrule, a hollow tube crimped to hold the hairs in place. The hair may be natural from a hog, badger or any variety of weasel, or synthetic. It is arranged, tied and glued by hand before being fitted into the ferrule. The ferrule is made of metals such as steel, and the better brushes are coated with silver or nickel. The hair of the brush is like the blade of a knife. The most important part of the tool must be held securely by its handle so the hairs don't become part of the canvas.
Quality counts in hair. The best hairs come from Siberia and China where cooler climates encourage thicker, fuller coats on the animals. Bristle brushes, used for covering the canvas and creating texture, are made from hog hair. The hairs of the bristle brush narrow at the top to form a wedge. Badger brushes, used for blending and softening, come from badgers as the name implies. The best hair is silver tipped and because the hairs are thicker at the end the brush is bushy. Less-expensive brushes, sold as badger hair, are made with white hair dipped in dye to create the effect of the silver tip. The best sable brushes are made from the tail hair of the Mustela or weasel from Northern China or Siberia. Lessor brushes use the hair of other members of the family. Kolinsky sable, from the Siberian red marten, is considered one of the best hairs and is used by Old Holland.
The ferrule secures the hair to the handle. Manufacturers may coat the metal with silver or nickel as an adornment, but application makes the difference. The well-crimped ferrule will hold bristles to the handle for years.
Some brushes such as the Kolibri have a constant handle length of 10 inches, while others vary even within the line of brushes from 6 to 15 inches. Other manufacturers such as Da Vinci and Escoda vary their handle lengths. The wood is dipped into paint up to four times and then varnished to ensure longevity. Thickness of the handle varies with the amount of hair used. The artist chooses the length of brush as it suits him. Some artists work nose to canvas when working on fine details and others prefer the distance.