silicone in bow rehairing

Martin Sheridan · #1 02-29-2008, 03:55 PM

Many years ago someone brought me a bow to rehair that looked like it had silicone rubber used for the bow tip wedge?

I was thinking about that today while rehairing a very poorly made bass bow that was more ready for the dump than orchestra use. The frog mortise was very poorly made and I had a devil of a time redoing it to get a wedge to fit properly.

So is anyone familiar with this and is it silicone or do you need a specific kind of silicone. I am of course not talking about using this stuff on good bows, but this bow wasn't even worth the price of a rehair and I'd use silicone or anything else that would be more practical than trying to remake a poorly made bow. And how is it used? Do you put the hair in or put the silicone into the mortise let it harden and then remove.

robobass · #2 02-29-2008, 04:35 PM

Wow! never heard of that. As far as your question about making the plug first or siliconing over the knot, Couldn't you tell on the bow you saw? You can get silicone mold rubber from casting supply houses in all hardnesses. You would probably want the hardest stuff available. It will be a two-part thing that you mix and then it chemically hardens. There are pourable types like smooth-sil 950, and putty types. You will need to get a can of aerosol mold release and spray the mortise liberally so the wedge can be removed easily. Also, there are two types of mold rubber. Tin based, and Platinum based. The platinum tends to be higher quality, but is easily contaminated by oils and things, which inhibit proper cure. The tin stuff is pretty idiot proof, and should work fine also, but might not be available in the hardness you want (Shore A 50 ought to do it). An extra precaution would be to spray a light coat of clear lacquer into the mortise first to seal it.

This stuff is almost blasphemous to talk about, but I have a cheap Chinese snakewood bow myself that has sloppy mortises. It actually plays really well, but my bow person probably won't agree to rehair it again. Maybe I will make some rubber wedges for her to patch things up!
Robobass

Bob Branstetter · #3 02-29-2008, 06:22 PM

Quote:

Originally Posted by Martin Sheridan

Many years ago someone brought me a bow to rehair that looked like it had silicone rubber used for the bow tip wedge?

I was thinking about that today while rehairing a very poorly made bass bow that was more ready for the dump than orchestra use. The frog mortise was very poorly made and I had a devil of a time redoing it to get a wedge to fit properly.

So is anyone familiar with this and is it silicone or do you need a specific kind of silicone. I am of course not talking about using this stuff on good bows, but this bow wasn't even worth the price of a rehair and I'd use silicone or anything else that would be more practical than trying to remake a poorly made bow. And how is it used? Do you put the hair in or put the silicone into the mortise let it harden and then remove.

It sounds to me that silicone would be far too much trouble for a cheap bow. Why not just drill a 1/32' or 1/16" hole and install a short nail ala Glasser? I see that done on cheap school bows all the time. It takes less than a minute to do it and you're on your way. Certainly not something for a good bow, but for junkers, it's can't be beat.

Michael Eisenman · #4 03-01-2008, 12:00 AM

Quote:

Originally Posted by Bob Branstetter

Why not just drill a 1/32' or 1/16" hole and install a short nail ala Glasser?

Can you explain about the nail? I'm having trouble visualizing where it goes and how it works, though I may come across it someday.

I'm getting my first rehairing lesson next week, and this interests me.

Also, would you have any ideas for sources of cheap bows to practice rehairing?

Thanks,
Michael

Bob Branstetter · #5 03-01-2008, 12:26 AM

Quote:

Originally Posted by low.eadg

Can you explain about the nail? I'm having trouble visualizing where it goes and how it works, though I may come across it someday.

I'm getting my first rehairing lesson next week, and this interests me.

Also, would you have any ideas for sources of cheap bows to practice rehairing

Thanks,
Michael

If you've not had a Roth-Glasser plastic bow frog apart, it's a little hard to explain. In an ebony frog the hole for the nail (brad) is drilled into the front part of the mortise just a little back of being 90 degrees to the slide. Once you see the inside of a Glasser frog this will make more sense to you.
Again - this is not something you would do to a non-junker bow frog.

Martin Sheridan · #6 03-01-2008, 11:38 AM

Roto Bass,
I just learned more about silicone. This stuff is white and pretty hard.

Bob,
I should have thought of that. I've done enough Glasser bows over the years. They use, as you know, a flat head screw and I think that would work as well? Do you use a slightly oversized nail for the drilled hole? Do you use a glue of some kind?

Back to the silicone, I have a feeling this stuff just comes out of a tube. After writing the original message I went through some bows that I recently bought here in Mexico and a couple of them have a white silicone plug. Several of the violin bows are Chinese and have a round hole drilled into the frog mortice rather than a true french style mortise so a screw, nail or silicone might be a good idea for these too?

Bob Branstetter · #7 03-01-2008, 01:02 PM

Quote:

Originally Posted by Martin Sheridan

Roto Bass,
I just learned more about silicone. This stuff is white and pretty hard.

Bob,
I should have thought of that. I've done enough Glasser bows over the years. They use, as you know, a flat head screw and I think that would work as well? Do you use a slightly oversized nail for the drilled hole? Do you use a glue of some kind?

You drill a hole just a little larger than the nail and down to the silver lining that touches the stick. The nail goes into the front of the mortise and make the nail enough so the flat head sticks up slightly above the top of the mortise. No glue is needs. The tension of the hair (and the bottom of the slide will keep it in place. The nice thing about a nail is there are no threads to grab or pull on the hair as you tighten the screw. You just slide the nail in front of the knot and into the hole.

Sent from my iPod Touch

Michael Eisenman · #8 03-01-2008, 06:05 PM

Quote:

Originally Posted by Bob Branstetter

If you've not had a Roth-Glasser plastic bow frog apart, it's a little hard to explain.

Talk about coincidence. Today my luthier loaned me a couple of bows to practice with, and one of them is a Glasser (don't know about Roth), with what surely appears to be a plastic frog. I might be in for a surprise when I open it up. Then I'll know what you're talking about.

Thx,
Michael

Bob Branstetter · #9 03-01-2008, 06:25 PM

Quote:

Originally Posted by low.eadg

Talk about coincidence. Today my luthier loaned me a couple of bows to practice with, and one of them is a Glasser (don't know about Roth), with what surely appears to be a plastic frog. I might be in for a surprise when I open it up. Then I'll know what you're talking about.

Thx,
Michael

Glasser and Roth-Glasser are the same thing. Roth-Glasser was the original name they went under for many years (when Scherl & Roth was the exclusive distributor).

robobass · #10 03-02-2008, 06:39 PM

I have seen the nail thing. It works. As far as silicone, if you're looking for something that just squeezes out of a tube, I can't think of anything except window caulk, but that might work. The advantage of moldmaking silicone is that it won't shrink as it cures. I agree with Bob that it's a lot of trouble to go to for ultra cheap bows, but for some mid-level bows with lousy mortises, it might be a good bet. The other thing is that the stuff is very cool in it's own right. Once you have it in the shop, you'll find other uses for it. Maybe even get obsessed!
Robobass

Bob Branstetter · #11 03-02-2008, 08:01 PM

Quote:

Originally Posted by robobass

I have seen the nail thing. It works. As far as silicone, if you're looking for something that just squeezes out of a tube, I can't think of anything except window caulk, but that might work. The advantage of moldmaking silicone is that it won't shrink as it cures. I agree with Bob that it's a lot of trouble to go to for ultra cheap bows, but for some mid-level bows with lousy mortises, it might be a good bet. The other thing is that the stuff is very cool in it's own right. Once you have it in the shop, you'll find other uses for it. Maybe even get obsessed!
Robobass

Bad mortises usually don't occur on anything but low level bows. I have occasionally had to get out the chisels and do some touch-up though. On the silicone, if it doesn't shrink, it is probably going to be a pain to get out the next time a rehair is needed. Unfortunately, bow customers have a tendency to come back a 2nd and 3rd time.

jimmyduded · #12 03-02-2008, 08:17 PM

for the nail thing, couldnt you take a dowel and thread it with a die and then tap the hole you drill(therefore making it more stable and easier to take out), just an idea

Bob Branstetter · #13 03-02-2008, 08:52 PM

Quote:

Originally Posted by jimmyduded

for the nail thing, couldnt you take a dowel and thread it with a die and then tap the hole you drill(therefore making it more stable and easier to take out), just an idea

Jimmy.
It doesn't get much faster than pulling out a pin. Take my word - the nail or brad method is quite stable. There are thousands of school bow in use daily with this modification. I can do it in about one minute. The idea here is something quick for cheap poor quality bows. What you suggest would probably take as much time to make as to rehair the bow. Time is money.

jimmyduded · #14 03-02-2008, 09:14 PM

good point, i wasnt taking into account that these bows are baisicly junk, what do those junk bows typically go for? they seem like they would cost les than a rehair

Martin Sheridan · #15 03-03-2008, 09:43 AM

With the cheapest of the Chinese bows it really is more cost effective for you and your customer to just replace them rather than rehairing charging just the normal cost of a rehair.

Someone asked about a source of cheap bows to learn rehairing on. Most shops have dozens of them they'd like to get rid up and would give them to you or sell them really cheap. Otherwise find a school. They usually have a lot of bows that need to rehairing and sometimes they don't have a budget.

I've found very few luthiers who like to rehair bows, but you either have to learn it and learn it well or find somebody who will do them for you.

Bob Branstetter · #16 03-03-2008, 09:57 AM

Quote:

Originally Posted by Martin Sheridan

I've found very few luthiers who like to rehair bows, but you either have to learn it and learn it well or find somebody who will do them for you.

I couldn't agree more. I'm always surprised when I find doublebass luthiers who do not hair bows themselves. I have always considered learning to hair bows (well) an integral part of learning the trade and a necessary evil.