Just as a mechanic may use wrenches and screwdrivers of different sizes with a variety of tips, an artist uses brushes of different materials and shapes to create differing effects. Fitch, a material used in paintbrushes, refers to either European or Asian polecats, or the ear hair of a black ox. Fitch hairs are short and smooth.
Because a fitch brush is made from natural hair, the outside of the hair is covered with natural scales. These scales help the hairs and the brush hold more moisture. Within each hair are hollow areas called medullas that also allow the hair to hold more moisture. A natural-hair brush such as a fitch brush will hold more paint colour than a synthetic-hair paintbrush. This allows artists the ability to apply paint more evenly and with longer strokes.
Fitch hair paintbrushes are affordable, and considered just as good as pricier red sable and Kolinsky brushes. Fitch hair brushes are sometimes marketed as Russian black sable. These brushes are particularly beneficial for artists who use Fitch brushes won't be as costly to replace as red sable or Kolinsky hair.
Chisel fitch brushes are a different type of fitch paintbrush. While they are not made from the same material as other fitch bruthses, they are so named for the shape of the brush tip. Chisel fitch brushes are wedge-shaped, with the hair receding from the sides. This shape allows the artist to paint very thin edges, and because the brush is made from natural fibre, it can hold more colour and deliver only a small amount to the canvas.
According to the Association of Restorers, fitch hair brushes are best for applying shellac. The natural hair holds a lot of shellac, just as it holds a lot of paint. This allows a restorer to apply shellac in longer, more even strokes. In turn, the shellac goes on more smoothly. This is important because shellac dries more quickly than paint. Not only does the fitch hair brush create a smoother finish, it saves the restorer time.