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The Strad December 2025 Edition

                                                          By Canisa Sie - Sielambowhair.com

                                                          Hair treatment

                                                    Musicians might not realise how important the quality and condition of their bow hair can be. Canisa Sie gives a guide to caring for this vital                                                        part of a string player’s arsenal.

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Bow hair is one of the most common and fundamental materials in a string player’s world. While technique, instrument and bow quality take centre stage, the humble bow hair quality plays a crucial role at the final point of contact with the string. It helps shape every nuance of sound and is surprisingly susceptible to damage.

A good rehair requires both high-quality horsehair and the expertise of a skilled bow maker or luthier. Such professionals know how the quality and traits of hair and bow—and the player’s style—influence the bow’s playability and sound. By understanding the key factors that affect the performance of bow hair and how to care for it, many common problems can be prevented by both makers and players.

Bow hair is a natural, organic material and, like wood, is highly reactive to its surroundings. It is hygroscopic, meaning it constantly breathes and releases moisture, stretches and contracts, sometimes within a single rehearsal. When it does, the bow may respond in ways that puzzle even experienced players.

In conditions of high humidity, bow hair stretches. Even when fully tightened, it can feel soft and unfocused against the string, lacking the resistance needed for control. Many years ago, a player from Germany preparing for a concert in Hong Kong during a particularly wet summer week found that the humidity remained around 90 per cent, and his bow hair stretched by nearly a centimetre. For help, he came to my father, a professional luthier, who did an urgent rehair for him so he could continue rehearsing.

Conversely, very dry conditions—such as seasonal interior heating in winter, or sudden exposure to strong air conditioning—cause the hair to contract. When humidity drops sharply, the hair loses its moisture, causing extreme tension that can pull the frog against the stick, causing discomfort and distorting the bow’s camber. Every year, I receive phone calls from customers reporting that their bow hair is snapping like dry twigs. These calls mostly come during the winter months, especially when rehearsals take place in overheated conservatoires, concert halls or spaces with heating systems. Humidity in these spaces can fall as low as 20 per cent. If the player happens to be seated directly under a heating vent, the effects can be even more severe. In such dry air, the hair becomes brittle owing to a loss of moisture, and is highly prone to breakage.

HAIR QUALITY AFFECTS EVERYTHING FROM GRIP TO TONAL CLARITY—AND ESPECIALLY RESISTANCE

Bow hair is rare: less than 5 per cent of harvested hair meets the standards required for professional-level playing, and for some top-quality hair, 99 per cent is discarded, leaving just 1 per cent as the crème de la crème for the most demanding musicians. High-quality bow hair is characterized by strong, straight strands with uniform thickness, uniform color, good elasticity and good resistance, clean and without blemishes. These features allow for consistent tension, a reliable grip and excellent response across the entire length of the bow. In contrast, common defects include curled or twisted strands, weak or brittle hair even from the same source, split ends, uneven diameter, and poor longevity of the hair.

Thus, hair quality plays a central role in bow performance. For makers, choosing the right bow hair is a critical task. Hair quality depends on working with a reputable supplier who understands details at each stage of processing at the source, and must be kept away from direct sunlight or overly dry conditions.

The difference between hair that responds beautifully and hair that lacks resistance affects tonal clarity and especially resistance, the essential friction that allows the bow to communicate properly on the string. A lack of resistance often stems from raw hair that is too thin, chemically treated or sourced from unhealthy horses exposed to poor feed or environmental stress. Defects such as uneven diameter, curled strands, and brittle texture can only be reliably judged by experienced eyes and hands by feel and appearance.

With high-quality hair on hand, experts also take climate into account when calculating the length of hair. The length of hair is not left arbitrary; it's adjusted based on seasonal or regional conditions. A bow prepared for the damp climate of the UK might be haired slightly shorter to accommodate for swelling. One for a player in Madrid, where summers are hot and dry, may require slightly longer hair to allow for future shrinkage.

Because horsehair is a natural material, no two batches are ever identical—even from the same source. That's why selecting and processing hair requires a careful blend of quality control and specialized skill for luthiers and bow makers. Proper sorting and selection ensures consistency and tonal qualities that no artificial materials can replicate.

Applied to high-quality hair, proper storage practices are crucial. Unopened bundles should be kept in a clean, stable environment with moderate humidity. Workshop storage areas may benefit from individually packed single-bow hanks, which reduce contamination or degradation. With good storage, unused bow hair can last up to three years. It's essential to ensure it's protected from pests like moths, and it's recommended to avoid purchasing excessive quantities at a time—preferring small batches like 250g hanks rather than 0.5kg or 1kg hanks.

SIMPLE CLIMATE CONTROL FOR BOWS AND HAIR

Fortunately, bow hair fragile needs the right care. Even small efforts can make a big difference.

DIY Humidifier

  • Lightly dampen a clean sponge or paper towel.
  • Place in a ventilated plastic container or ziplock bag with small holes.
  • Keep inside your instrument case or hair storage drawer, avoiding direct contact with the hair.
  • Refresh regularly.

DIY Desiccator

  • Use silica gel packets, dry rice or salt in a breathable fabric pouch.
  • Place it in your case or drawer.
  • Remember to replace or recharge the system periodically.

GOLDEN RULES FOR BOW HAIR CARE

  • Avoid prolonged exposure to high temperatures or direct sunlight.
  • Keep bows away from heaters and air conditioner vents.
  • Humidity below 45 per cent: use a humidifier.
  • Humidity above 70 per cent: use a desiccator.
  • Store bow hair in a cool, stable environment.
  • Open only small quantities at a time—250g rather than 0.5kg or 1kg hanks.