Bow hair removal

September 12, 2016 at 02:25 PM · I went in for a bow rehair and got much more hair than is recommended for my bow. Although I went to one of the best shops in town and the hair is really good quality, the sound it pulls is less sweet and clean if the bow has over 120 hairs. Is there a safe way to remove some hairs? I read you can use a box cutter to cut off hairs, one by one, at the very end where they meet the bow. Is this safe? Also, I read you should remove hairs evenly from different sides. Any suggestions for a quick cheap fix?

Replies (27)

September 12, 2016 at 02:47 PM · If you want to be super accurate, and very certain that you want to remove the hair, I use nail clippers to cut broken strands from my bow.

September 12, 2016 at 03:36 PM · NO! Go back to the bowmaker and express your concerns.

September 12, 2016 at 04:02 PM · With a Sawzall.

No, seriously, I agree with Raphael. Why pay for a pro rehair if you have to fix it yourself (non-professionally) when you get home?

September 12, 2016 at 06:06 PM · Over 120 is 'too much hair'?

I always read/heard the hair count was anywhere from 150 to 200 hairs on modern bows. Less on baroque bows.

But ultimately how many hairs the bow gets has to do with how it was made, how stiff it is.

But yeah if you're not happy, go back and express your concerns.

September 12, 2016 at 06:06 PM · Don't start in on bow de-hairing; uneven hair will warp your bow for sure, due to the uneven tension (hairs are installed as a group, not one at a time, or by count). Please go back to talk with whoever did your rehair.

I am curious about how you arrived at the 120 hair rule: does this take into account the hair diameter, weight and specific gravity, or just the number of hairs regardless of mass? How many hairs are on your bow?

September 12, 2016 at 07:49 PM · Are you sure you put enough rosin on the new bow hairs, that could be your problem.

September 12, 2016 at 07:57 PM · I have a carrera by jonpaul. There's a thread on comparing various carbon fiber bows, including the number of hairs from factory. Codabow Luma: 188 hairs. Codabow joule: 167. Jonpaul carrera: 122 hairs. Coda bow classic:214 hairs. Coda bow conservatory: 150 hairs. Erin, I know hairs have different diameters and weights, and I don't know the specific gravity pull here in the big apple. Just want to know the best way to remove hair in case I don't want to subway back to the bow repairman

September 12, 2016 at 07:57 PM · How do you know how many hairs are on your bow?

September 12, 2016 at 08:03 PM · Lyndon has an excellent point--more rosin! You can play your violin with a wire coat hanger if it is properly rosined. Sounds like you don't want to make the subway trek; how about a phone call?

Dexter, If this is the thread you are referring to, I don't see that 120 is the magic number... however, it does say a student bow does not do well with too much hair, so you might be right about being over-haired! But if so, the bow may need less hair and a bigger plug, not a DIY job. Good luck!

September 12, 2016 at 08:25 PM · Erin, here's the thread I found with the hair quantity info

Lydia, I'm not sure, how many hairs are on mine post rehair... I've started counting several times and got bored in the process... it does look like a lot more than I had before the rehair. When I went to the shop I told the lady at the counter I wanted 122 hairs, and she looked at me like "really?" She just wrote down on the order to rehair with the same amount. If there's no home fix, so be it.

Lyndon, the bow has plenty of rosin.

September 12, 2016 at 08:41 PM · Well, I am interested in this, so I emailed JonPaul. I wlll let you know their answer!

September 12, 2016 at 08:47 PM · "You can play your violin with a wire coat hanger if it is properly rosined.

Holycrap they're right! Doesn't sound too good but it works!!

September 12, 2016 at 09:24 PM · I went through this 15 - 16 years ago. I measured the elasticity of about 30 bows (violin, viola, and cello) and I went through a lot of effort trying to establish the optimum hair stretching that was best for bow sound and determined how many hairs (of random thickness) would be needed for each bow. I even made a portable rig for making the stick elasticity measurements and Jay Ifshin had agreed to let me use it on bows in his shop. And then 9/11/2001 happened and I decided to quit all that and just play music. While I had a website, my Excel chart of that bow data was available on line.

I counted bow hairs - that's how I knew how many each bow had. And I removed bow hairs with an Xacto knife, inserted to remove a few hairs uniformly across the inside of the hair ribbon and being careful not to interfere with the hair fastening in the frog or tip.

I've had no trouble with the resulting "hair cuts" some of which go back 16 years, and some are more recent. I tend to find that some of my more flexible bows have been too richly haired. The one that can tolerate it least is a Berg Deluxe violin bow that's pretty much just "hung on the wall" since I had it rehaired, but I gave a "hair cut" a few weeks ago and it now seems to live up to its recommended price and former behavior.

A very stiff stick can tolerate a lot of hair. A flexible stick needs less hair if it is to retain any camber when optimally tightened.

I wish bow technicians would hair bows according to their needs, but I've not had that experience during the past 20 years. I have a lot of bows and a tech who just grabs a premeasured hank of Vl, Va, or Vc hair is not going to hit in on the mark every time, and a tech who does it any other way will likely have to charge more than $60.

AND WHILE I'M AT IT: I'm also a "hair cleaner." I use alcohol pads to remove old rosin from my bow hair when it seems time for a rehair. I can't get it all the way back to "new hair" condition (even with 8 alcohol swipes alternating with 8 clean-cotton-cloth swipes), but it keeps me on my side of the bay for a while longer. There is no risk in this since if cleaning the hair doesn't do the job, I'll just drive across a bridge to my luthier for the rehair, and have lunch out while I wait.

September 13, 2016 at 02:56 AM · As long as we don't get "hairing impaired!" ;-D

September 13, 2016 at 07:58 AM · What we all need is "hair of the dog."

September 15, 2016 at 05:46 PM · I decided to go ahead and bring it back to the shop today and had some hair removed by the technician. The sound improved 100% and the bow is back to its old glory, and all it needs is very little tension/tightening of the hair to produce the sound I love to hear.

Thanks Andrew for the very informative post. If you have two identical bows and one is haired with 100 hairs and the other one with 200 hairs, tightened to the same degree, the one with 200 hairs will have twice as much tension since it has to stretch out 200 hairs instead of 100, in turn becoming less flexible. I did call the manufacturer a few days ago to check on the magic number of hairs for my specific bow, and he said there wasn't, it all depends on the diameter and other specs of the individual hairs. however, everything else being equal, I personally believe my bow does better with much fewer hairs (around 120) than most.

September 15, 2016 at 11:24 PM · I'm not a physicist but I think the tension depends more on the stiffness of the stick than the number of bow hairs???? Not that the hairs aren't a factor.

September 16, 2016 at 03:13 AM · I am most happy to hear you achieved what you wanted!! Nice work!!

September 16, 2016 at 03:27 AM · Lyndon, tension on stick would remain the same, but tension on individual hair would differ. More hair = lower tension on hair. I am by no means bow maker, but I'm sure there are some out there, who can somehow relate this to the sound that the bow makes.

This discussion thread makes me really curious, and makes me want to experiment with my bows.

With my 2ndary bow, after I bought it, and broke few strands of hair, it actually sounded better than when I first got it. It is due for rehairing soon, maybe I'll try Andrew's hair cleaning a go.

September 16, 2016 at 04:09 AM · what you said makes sense, hence a stronger stick might be comfortable with more hairs, however that's not what Dexter said, at least as I read it.

September 16, 2016 at 04:22 AM · Actually, that is what Dexter said, I think he just stated that from the POV of the stick rather than the hair.

September 16, 2016 at 07:17 AM · If you tighten the bow the for same tension (deflection) on the stick there will be half as much tension per hair(or is it square root of 1/2 tension??) for 200 hairs as for 100 hairs, not twice as much tension as Dexter said.

the hairs will collectively have the same resistance to deflection by the strings whether there are 200 hairs or 100 hairs, if the tension on the stick is the same.

September 16, 2016 at 08:57 AM · I miswrote but Andrew got my point. It should be from the point of view of the stick. The more hairs, the less flexible the stick becomes. If that premise is true, then, is stick flexibility a good or bad thing?

September 16, 2016 at 09:20 AM · ???????????????? I think the flexibility of the stick is pretty much a constant.

Tension on the stick is determined by the correct deflection of the stick away from the hair, Usually recommended as the thickness of the stick away from the hair. The tension on individual bow hairs is not the important factor and is not possible to measure when tightening the stick, suffice it to say that tension on individual hairs will be greater with less number of hairs, but that's not what's important, its the tension on the stick that is important.

September 16, 2016 at 01:31 PM · The thing is, the hair and stick work together. The tension in the individual hairs has to reach a certain level for the hair to work properly. This tension in the hair is caused by the force from the bending of the stick. If you have 200 hairs the bending of the bow will have to be twice as much as if you have 100 hairs. Anders Askenfelt's work has shown that the hairs have to be at a certain tension (that causes them to stretch a certain amount), therefore it is clear that more hairs will necessitate grater distortion of the bow stick for optimal bow performance.

I quote below what I wrote in my "Bow Calculator" EXCEL spreadsheet back in 2001 based on measurements I was making:

"My measurements gave elastic properties of a single hair as 0.79% per Newton = 0.0079m/meter of hair/N/hair = 0.0774 m/m/kg. Or, this could be given as 126.6 N/meter deformation/meter of hair/hair or 12.9 kg/m/m = 0.0198kg/mm/ bow hair length = 0.194 N/mm. The optimum hair strain for best sound seems to be 0.5 mm, so a force of about 2.5 grams /hair will cause this. A normal force of 0.15 gram will move the hair 1 mm closer to the bow stick. The moments of the forces on the bow (1) bow weight, (2) resolved finger force on bow, and (3) string force on bow hair

are resolved about the right thumb as a pivot. So for an optimally tightened bow the required finger force about 60 mm

from the right thumb can be estimated from the normal hair deformation.

Anders Askenfelt has reported a Young's modulus for bow hair in the range 4.9 Gpa (GN/m^2), or about 0.2 N/mm (very close to my measured value of 0.194 N/mm) for a single hair, with hair elastic up to about 4 N. His measured hairs averaged 0.20 mm ± 0.05 diameter, with a mass (0.65 m long) of 0.03 g/hair and density between 1200 and 1400 kg/m^3."

September 16, 2016 at 02:19 PM · In other words if you have too many hairs and a weak stick, the bow is unplayable.

September 16, 2016 at 02:25 PM · Thanks Andrew, this all just confirms what I suspected.

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