According to Joan Balter, a bow maker and repairer in Berkeley, California, stallion hair from Siberia is generally considered the best. For various reasons, the kind of horsehair used makes a difference in the quality of the final product. Horsehair from animals in northern climates tends to be stronger, which Balter explains is nature’s response to coping with more frigid temperatures. The gender of the horse is also important; stallion hair is preferred because it is generally cleaner than that of mares, which tends to get hit with more urine spray.
Other factors that affect quality are consistency and color. Both players and bow makers value straight hair. “Hairs with irregular structures will cause weird, scratchy sounds,” says Balter. “It’s like hitting a pothole in your car.” Many bow rehairers prefer white hair, particularly for violins and violas, because the hair of this color is usually finer in texture. (There is, however, some disagreement about the extent to which color correlates with textural differences that affect the sound.) Many basses and some cello players use the coarser black hair, which some say is “grabbier,” while others opt for a salt and pepper combination.
Horsehair is collected and processed in specific ways. Although some Chinese hair is cut from live animals, most hanks of horsehair are slaughterhouse byproducts, gathered from animals that have been killed for their meat, hide, and hooves. The hair is first cleaned with a mild soap or very mild detergent, then “dressed” for use in numerous products (which include baskets and brushes, to name a few items; bow hair comprises a relatively minor part of the horsehair industry as a whole). “Dressing” the hair involves gathering it up to make sure all of the hairs are approximately the same length; those that are too long or short are picked out, and the ends are evened up.
At the same time, dressers check the hairs for straightness, strength, and consistency. Much of what constitutes high-quality hair depends on how it is dealt with at this stage. Hairs that are too short won’t fit into a standard bow, hairs with split ends will snap, and irregularities in the hair shaft can affect the sound, so dressers must be selective.