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 ARCHIVED TOPIC: Bow hair electron micrographs


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Learner - Posted - 02/12/2011:  10:53:09


Hello all:

I've seen various pronounciations from learned folk (and some not so learned) about whether bow hair has "scales" or not. Some say yes, some say no. Some say that it has little "hairs" on the surface.

Today I actually got to see electron micrographs of bow hair! An electron micrograph is a photograph taken of an image that is seen by means of an electron microscope, which is a very, very powerful microscope. These images were taken at 500x magnification.

Well, I was surprised: bow hair really does have what appears to be "scales" of a sort. Actually more like "ridges" that run perpendicular to the length of the hair (across the width of the hair).

It reminded me of a roof with shingles that have the edges chewed up a bit. There didn't appear to be "individual" scales, where 3 sides are free and the back end attached. But definitely wavey ridges that are scale-like in form. I couldn't see if under each ridge there was a significant space or not. That would have needed a higher magnification.

There were three photos that I saw. Each bow hair was about 200 uM in diameter. There were no little "hairs" on the surface of the bow hair. Just the scaley ridges. There were also a few areas where there were no ridges at all.

The luthier who had these taken told me that he regularly shows these photos when he gives talks, and people get into debates as to whether bow hair has scales or not. He had them taken at a local research facility. He says that the scaley ridges are what the rosin holds onto.

He also said that using alcohol is a bad idea for cleaning bow hair. He seems to think that it would dissolve the rosin, which would then get under the ridges, rather than being completely removed from the hair.

I've asked him I could post the pictures here. If he does give me the photos to post, I attach them to this thread.

Best wishes,

Frank


Edited by - Learner on 02/12/2011 10:55:27

bj - Posted - 02/12/2011:  10:56:25


Sweet! I look forward to seeing them.

woodwiz - Posted - 02/12/2011:  11:01:16


Here's almost everything you'd want to know about the subject:

iwk.mdw.ac.at/Forschung/englis...whair.htm

The scales aren't very relevant, IMHO. They don't make any sound without rosin. Judging by the amount of effort it takes to rosin up a new bow, they don't appear to have much effect in holding rosin, either. As you can see in the photographs, the rosin adheres in relatively large blobs.

There's no place for rosin to get in under the scales. Experience shows that cleaning bow hair with alcohol works fine, and extends the useful life of the hair by getting contaminants off of it.

M-D - Posted - 02/12/2011:  11:02:42


Such photos are also available on the 'Net, some place. Seems like the link was posted here, once upon a time.

Learner - Posted - 02/12/2011:  11:08:02


Well, I didn't even have to see if I could get the pictures from him. Here are some I found online:



This first is horse tail hair at 200x, far less than the magnification I saw. Only the ouline of the ridges are visible:






This next one is horse body hair at 300x. The scaley ridges are now visible:






And this final one is horse mane hair at 2000x. The scales themselves here are clearly visible. They do have spaces under them. What is not clear is whether the scales on the tail hair would look the same at this magnification:




Frank


Edited by - Learner on 02/12/2011 11:09:31

DougD - Posted - 02/12/2011:  11:15:01


Here are some pictures of bowhair from different regions. I don't know the magnifications: polychord.at/xchange_advanced_...php?ID=18

Whoops, I see that woodwiz had already posted a similar link. I found one with the titling in English.


Edited by - DougD on 02/12/2011 13:43:54

transplant - Posted - 02/12/2011:  13:16:33


Even if dissolved rosin can get "under the scales" of the bow hair, I wonder what problem(s) that is supposed to lead to... Only times I use alcohol on bow hair is when it gets grubby-looking from finger dirt, or if it has oily contamination that affects the sound in spots. Makes an improvement, doesn't cause problems.

layne - Posted - 02/12/2011:  14:27:23


Alcohol doesn't affect my bow either, but it most definately affects my bowing...

emilysweet - Posted - 02/12/2011:  19:13:28


Who was the luthier that shows these pictures I wonder. I'd like to see similar pictures with rosin dust on the hair to see how the rosin "gets under the ridges". I suspect the rosin particles are too large to fit under there and as Woodwiz suggests, they have little to do with holding rosin in place.

I always refer people to Norman Pickering when it comes to discussions about rosin and bow hair. He has studied it extensively.

RobBob - Posted - 02/13/2011:  06:05:00


It is just like the old time told me many years ago. He didn't have any of this technology to back him up just the authority invested in him through experience. And fact he knew what he was talking about.

woodwiz - Posted - 02/13/2011:  08:44:24


Horsehair with and without rosin:


Edited by - woodwiz on 02/13/2011 08:45:28

Learner - Posted - 02/13/2011:  12:34:10


quote:
Originally posted by emilysweet

Who was the luthier that shows these pictures I wonder. I'd like to see similar pictures with rosin dust on the hair to see how the rosin "gets under the ridges". I suspect the rosin particles are too large to fit under there and as Woodwiz suggests, they have little to do with holding rosin in place.

I always refer people to Norman Pickering when it comes to discussions about rosin and bow hair. He has studied it extensively.

He is a local luthier that I use.

HIs comment was directed towards what happens when the rosin would get dissolved by the alcohol. I didn't ask him why rosin getting under the scales would be a problem. He's been "luthering" for many years, and is an older man. I usually give the benefit of the doubt.

However, there have a been few occasions now when I've posted comments of his here, with the result that others disagree with his conclusions. So I'm learning that his viewpoints are not shared by all, and that he could be wrong at times.

Frank


Edited by - Learner on 02/13/2011 12:46:49

Learner - Posted - 02/13/2011:  12:46:13


Thanks for the comparison photos, Michael.

I had read an article somewhere about how rosin works. One of the points made was that friction causes the rosin to stick the bow hair to the string, which at some point when the tension builds up enough, will then release, causing the string the "snap back". This then happening hundreds of times a second causes the string to vibrate.

From the appearance of the photo, the rosin looks as though it is not deposited on the strings as individual large particles, but sort of like flattened blobs, or like a liquid that has been spilled, pooled, and dried on a surface.

I could see how the scaley ridges would provide a substrate to which the rosin could preferentially cling. The strings themselves have windings, with grooves where the rosin can lodge. The bows hair has the scaley ridges, which could also aid the adhesion of the rosin to the bow hair.

What would be interesting would be to have a controlled experiment to see if rosin clings better to fresh bow hair, versus hair that has been heavily used. If very used hair has less scales left on the surface, then possibly the rosin would not adhere as well?

Frank

FiddleJammer - Posted - 02/13/2011:  13:04:15


On my wish list, I'd like to see the magnified horse hair picture next to some pictures of magnified fiddle strings. :-)


Edited by - FiddleJammer on 02/13/2011 13:05:00

transplant - Posted - 02/13/2011:  13:59:56


Looks like the rosin melts and smears onto the hair.

I bet the hair next to a string would look like a piece of clothesline next to a telephone pole.

I have an easier time believing that alcohol can help wick rosin in between the windings of a string. I do believe that loading a string unevenly along its length makes for that false sound of a worn-out string.

mudbug - Posted - 02/13/2011:  14:44:31


If the "scales" are microscopic, isn't it a moot point on a full- size, smooth hair?

giannaviolins - Posted - 02/13/2011:  14:51:39


Rosin melt, weld to string, pull string, bond breaks, string moves, repeat.

See Helmholtz.

Learner - Posted - 02/13/2011:  18:02:26


quote:
Originally posted by mudbug

If the "scales" are microscopic, isn't it a moot point on a full- size, smooth hair?

Well, that brings up an interesting point, Steve.

I saw a special report several months back. Researchers had been puzzled for years as to how a gecko can walk vertically up any type of surface, even glass. They don't have suction cups of any such thing on their toes.

It turns out that they do have hundreds of thousands of sub-micron thickness superfine filaments on the surface of their feet. These hairs are so small that it is believed that they adhere by means of van der Waals force with the molecules of the surface on which they are walking. Pretty amazing. When it was first discovered the researchers were pretty amazed.

Anyway, it's not impossible that at the size level of the bow hair scales that forces between them and the rosin could be considerable. Also possibly not. But just because the scales are small does not mean that they don't play an important part.

I have heard that there is "synthetic" hair that is used on cheap bows. I wonder what the surface on this material is like? Does it have any ridges that could help with rosin adhesion? Maybe someone here has seen micrographs of this material, and could comment.

Frank



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