Violin Forum/Message Board

Mikes · Posted: Tue Jan 25, 2011 11:10 am Post subject: Bow hair length

A friend of mine just bought a new wood bow and she is unable to back off the tension enough to slacken the hair. The hair is about 3/8" off of the stick at it's most relaxed point and the screw starts to untheard itself if you try to lossen it anymore. This doesn't seem quite right to me so I thought I'd ask what is acceptable for a new bow? Is it harmful in anyway to keep the bow tensioned all the time? Would it have to be rehaired to correct this?

bata · Member Joined: 12 Jan 2011 Posts: 30 Location: Ontario

The hair when relaxed should easily touch the stick. The hair will lengthen and shorten as per the dryness and humidity in the air. Has the bow been kept in the a very dry location? If so that might explain the short hair. Its not a good idea to keep a lot of tension on the bow as it could distort the stick. The hair should be relaxed every time it is not being played. I would advise your friend to let a luthier take a look at it. It could be that the hair has been incorrectly installed, in which case it would have to be re-haired. There are more experienced bow people on this forum than I, so would like to hear their take on this.

Lemuel · Posted: Wed Jan 26, 2011 1:43 pm Post subject: Re: Bow hair length

Michael Darnton · Posted: Thu Jan 27, 2011 9:17 am Post subject:

Hair changes in length quite a bit with changes in humidity. The original meters for measuring humidity used a pointer with a hair fastened to the short end hanging out past the pivot point as the object that changed with humidity, moving the pointer.

In the summer, or when/wherever the bow was rehaired, it was probably fine. The objective in rehairing is to keep the hair as short as possible, minimizing the distance between the frog and the leather thumb grip when the bow is tightened. If this is achieved in the summer, the hair will be too short in the winter, but since pros have their bows rehaired quite often, it isn't a problem.

When the hair is loose, there shouldn't be any stress on the bow. If you're perceiving the hair as having tension when it's loose and yet the frog has moved as far forward as it can (so that it touches the leather grip), that should be taken care of, to protect the bow from breaking behind the head, where it's weakest.
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Mikes · Posted: Wed Feb 02, 2011 10:49 am Post subject:

In this case the brass eyelet bumps into the North end of the mortice that it slides in well before the tension on the hair is released. I can see that it's not a huge problem, but I was more curious about what the standard is.

Lemuel · Posted: Fri Feb 11, 2011 4:37 pm Post subject:

Michael Darnton · Posted: Fri Feb 11, 2011 7:10 pm Post subject:

Yes, that would work, but only for as long as it would take for the bow to dry back out--a couple of hours, probably. The hair doesn't have any way to hold more water than it does, which depends on the external humidity. If it's dry outside, the hair dries to equal that.
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Chet Bishop · Posted: Sat Feb 12, 2011 6:20 pm Post subject:

A possible variation on that solution would be to dampen the hair until it was as slack as you could hope for, then anchor the ends immovably in some way and allow it to dry completely at maximum length. The hair would either stretch or break, I think. If it stretched, I think it might stay in that shape semi-permanently.

The reason I think so is that I had been warned that some unscrupulous hair-supply companies were doing something of that sort, and selling the "longer" hair at a premium. Once the hair has been wetted, and allowed to return to normal it is shorter than when sold. (I think Lynn Hannings issued this caveat some time ago, from her experience. And the hair she sells, she has checked by wetting and allowing it to dry normally.)
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Lemuel · Posted: Sun Feb 13, 2011 5:10 pm Post subject:

Michael Darnton · Posted: Sun Feb 13, 2011 11:22 pm Post subject:

I don't know. We see it here a lot. But we often have 90% humidity in the summer, and right now we're fighting to keep it above 30% in the shop. Without humidification, it's 20%. Maybe it's the range of the swing.
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bata · Member Joined: 12 Jan 2011 Posts: 30 Location: Ontario

Hi,
I found an old bow in my scrap box that seemed very similar to what was being described in this discussion i.e. with very tight hair when the frog is fully relaxed. As can be seen the hair was so tight that the stick is almost going into a reverse curve.
I live in Ontario and the air is extremely dry this time of year
Out of curiosity I placed the bow in my shower cubical at 10:00am. I had used the shower at about 6:45am with the exhaust fan running, so the bathroom did not get too steamy. The shower had not been used upto placing the bow inside, for 3 1/4 hours. I checked every 10 minutes and after 40minutes the bow hair was totally relaxed. The difference can be seen in the before and after pictures below. Nothing on the bow was touched between the taking of the pictures. After removing the bow from the cubicle, it was hung in my workshop, after an hour it had returned to its former tight hair condition.
I am wondering if there is a great difference in hair qualities that would contribute to this. Is all hair equal? I know that with human hair it changes as per the day i.e. bad hair days and anything from fine to course, thick to thin.
Is bow hair graded in any way? I dont recall seeing any grading symbols when buying new hair. I believe that unbleached Mongolian mare tail hair is supposed to be the best, but how can one determine the quality of the hair prior to purchase?
Regards...Tony
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