One of the most common questions we get at the shop is “How do I know when it’s time to rehair my bow?” There are a couple of different indications that it’s time to get a rehair depending on what you notice happening with your bow.
One of the first and most obvious indicators is that the bow hair near the frog is really dirty. Your hand produces natural oils while you are playing, which will cause dirt and grime to collect on the bow hair. When the hair is dirty it loses its grip. Grimy build up is essentially shortening the amount of hair on your bow that you can use.
Bow hair can be cleaned using denatured alcohol but you have to be extremely careful using it. If any alcohol gets on the bow stick itself, it can dissolve the varnish on the wood. If there is substantial amount of grimy build up on your bow then really the best thing to do is have it rehaired.
A second indicator that it’s time for a rehair is if you have lost a good amount of hair on the bow, or you have lost a lot of hair from one side of the bow. Losing hair on one side of the bow will start to affect how you balance your bow and it may lead to you grinding down on the bow stick.
A third indicator that you’re in need of a rehair, that may not be as obvious to see, is when the bow hair has been stretched out too much. If you feel like your bow is becoming too bouncy or the balance point has changed than it probably means that your bow hair is stretched out.
A good way to check this is to loosen the screw on your bow all the way until the screw thread is disengaged. Slide the frog forward on the stick until it butts up against the thump grip. At this point you will see the bow hair sagging below the stick. If the bow hair is sagging at the level of the stick or just slightly below it then it should be fine. If the bow hair is sagging way below the stick then it’s time for a rehair.
If you live in a climate that is prone to substantial temperature changes between the seasons (New York for example) then you may find that you will be in need of a rehair during the spring or the fall. Bow hair, which is essentially horse hair, is sensitive to humidity and can shorten or expand depending on the level of humidity in the air. An increase in humidity in the late spring months can cause the bow hair to stretch too much, while a depletion of humidity in the fall months, can cause the bow hair to shorten too much. Bow hair that is too short is dangerous in that the tension can cause the head of the bow to snap off.