• Frequent hair breaks, which might be about a bow-instrument mismatch, or the player is trying to force a sound (too firm a grip and pressure on the strings) that isn’t there.
• Seasonal weather conditions, or travel to a different climate, can affect the humidity and relative dryness and length of the bow hair. The dryer the conditions, the shorter and therefore more tense the hairs – perhaps too tense, leading to breakage.
• Bow bugs, the tiny mites that love dark places (inside cases) and the taste of horsehair, can destroy the bow hair in a few short weeks. Sunshine can go a long way to scare them out of a case; hair damage still needs to be addressed.
• Accumulated dirt on the hair, from human hands and sweat or the rosin and ambient dust, can compromise the horsehairs as well. Clean with a soft, clean dry cloth is recommended; veteran violinmakers often advise that detergents and solvents can cause more harm than good.
With the cost of a simple rehair priced at only around $65, players are urged to take their underperforming bows in to a violin shop for examination and a repair. It just isn’t possible for the individual musician to do it at home. The proper workspace and tools are required, not to mention the expertise. With frogs, horses and abalone already involved, it’s quite all right to hand the job over to a professional.