The question of humidity, and how it effects your bow

Ever noticed how your bow hair seems to change day by day? One day it feels perfect, the next it's a bit… off. The biggest culprit behind these subtle shifts is humidity. It might seem like a small factor, but understanding how humidity impacts your bow hair can help you to extend the life of your rehair and can explain those days were your bow hair seems to be a bit all over the place.

Think of bow hair like a living thing – it breathes! As humidity levels fluctuate, the hair responds by expanding or contracting. High humidity means more moisture in the air, causing the hair to stretch. Conversely, dry air causes the hair to shrink. This might sound abstract, so let's look at a real-world example.

Consider the process of a bow rehair. A key step in the bow rehairing process is wetting the hair by soaking it in cold water for a short duration. This technique serves two main purposes: it facilitates even pulling of the hairs for knot tying, and it ensures uniform moisture levels across all strands. This uniformity allows for accurate measurement of hair length, as all strands will shrink at approximately the same rate when dry, resulting in even tension. When the restorer ties the final knot, they account for this shrinkage, making the hair slightly longer than required. Once dry, the hair should contract to the desired length, as calculated by the restorer. This understanding of humidity's effect on hair is essential for achieving consistent results in bow rehairs.

So, what does this mean for your bow? Well, let's say you get your bow rehaired, and the hair is beautifully even. You take it home, and it's raining outside. Even though your bow is safely tucked away in its case, the relative humidity inside the case, after being outside on a rainy day, is likely higher than in your warm, dry home. When you open your case, you might find that the hair looks slightly uneven. Don't panic! This is simply the hair absorbing moisture and stretching slightly. If you are lucky enough to have a nice warm home, the relative humidity will be lower than the humidity outside, which means the hair will shrink back to it’s original rehaired state over time*.

This is why we always recommend loosening the hair on your bow after each playing session. If you store your bow in a drier environment, the hair will shrink, putting extra tension on the bow while in its case. If you hadn’t loosened your bow before putting it back in it’s case, the hair can now become over tightened without you realising! This can lead to broken hairs or prematurely stretch the hair, meaning a shorter time between rehairs.

There's no way to completely eliminate the effects of humidity on your bow. However, being aware of how it works is key. You might find that on humid days, you need to tighten the bow a bit more to achieve your usual playing tension. On dry days, you might need to tighten slightly less than normal.

The best preventative measure you can take is a simple one: always loosen the hair on your bow when you're finished playing! This small habit will significantly extend the life of your bow hair and help you maintain a consistent playing experience, no matter the weather.

*There is a caveat to this, which is if your home has a higher relative humidity than the workshop in which the bow was rehaired, it might not ever look exactly how it did when you picked it up but will still work just as well.