horsehair, animal fibre obtained from the manes and tails of horses and ranging in length from 8 inches (20 cm) to 3 feet (90 cm) and most often of black colour. It is coarse, strong, lustrous, and resilient and usually has a hollow central canal, or medulla, making it fairly low in density. Hair taken from the mane is softest and ranges from 50 to 150 microns (a micron is about 0.00004 inch) in diameter. Hair from the tail, coarser and with greater resilience, ranges from 75 to 280 microns in diameter and is marketed separately.
The longest hairs are used for fabrics; medium lengths are used to make bristles for paint, industrial, and domestic brushes; and very short hair is curled for use as stuffing in upholstered furniture and mattresses. High-grade white horsehair is used for the strings of fine violin bows.
Horsehair fabric, or haircloth, stiff and with an open weave, is usually made with lengthwise yarns of another fibre, such as cotton, and long, crosswise yarns of horsehair. It is used as interlining or stiffening for tailored garments and millinery but is gradually being replaced for such purposes by materials of synthetic fibres. The fabric, at one time made into shirts worn by religious penitents, became a popular upholstery material in the 19th century. Horsehair for the textile industry is exported chiefly by Argentina and Canada; other producers include Mongolia, China, and Australia.