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nathan slobodkin

Why do bridges bend?

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I had a cello come in today with an absurdly warped bridge and was wondering why you find some Hill and Wurlitzer bridges which are straight as the day they were made after 50 years while others seem to warp in no time. I also realized that I never see warping of bridges while they are in my shop although some times they will come back a year after they sold and the bridge needs to be straightened. 

I am quite rigid about not using any blanks until they have been drying in my shop for at least five years and I cut to the patterns which I was taught in the J. Francais shop. On nicer instruments I use Aubert DeLuxe blanks And on lesser ones Aubert #7 violin bridges  and #16 cello blanks. I always select the most compact narrowest grain I can find.

My own violin has had the same bridge for many years with no sign of any changes and I know some of my bridges have remained straight after as much as 20 years.

What is the story on this? Is it just that if you keep the bridge straight it won't warp? The wood? Luck? My guess is that some of the Hill bridges warped as well but therefore were replaced so I don't see them but it certainly seems worth thinking about.

I know Rene Morel once told me to rub a little shellac on the inside surface of cello bridge legs that some makers at the Cremona school in the 70's were spraying artist chalk fixative on their bridges and that Nigogosian and some other makers heat treat(ed) their bridges. Other than instructing clients to check their bridges carefully and correct any tendency to lean what can be done about this.

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I woild guess the main cause is not keeping them at  the correct angle, especially while changing strings. I have sold a few violins that were set up at the same time a couple I kept were; all the bridges were cut the same, from the same batch, and seven years later mine are still perfect, while a few I sold warped after less than two years....and some string changes.

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If they are properly cut and fit, then I usually consider it to be the fault of the musician for not maintaining the proper placement and straightening it up. It is seldom that an instrument comes into the shop that I do not need to straighten the bridge. They are almost all leaning toward the fingerboard. I try not to lecture, but sometimes it is difficult. 

Now, a long discussion on what constitutes a "properly cut" might have to happen. I recently saw an ugly bridge that i cut 16 years ago that was perectly straight, but I do feel that sometimes it is a bit of luck in that the bridge blanks that we get today are not the quality that you were working with at Fraciais' decades ago.

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Players, be they students, amateurs or professionals, just DON'T STRAIGHTEN THEIR BRIDGES after tuning, and after even a week, they lean towards the fingerboard. At every lesson I give, I have to pull back bridges and re-seat strings, and I even find myself offering that service to colleagues at rehearsals! I once had a colleague, a violist of course, who turned down my offer to pull back his bridge, because he liked the way his viola was sounding and didn't want anyone to mess with his bridge except his favourite luthier. I guess it's not impossible for a bridge to warp on its own, but in my experience the main culprit is the player!

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Much as I would like to blame this totally on the players I think there are other issues at play. Thinking about this further it strikes me that I really don't see ANY warped bridges from the greatest old shops and despite the very small sample group I think I would occasionally see one if the players (already established to be serial fiddle abusers) were the only factor. I was just looking at a Moennig bridge which had been on a cello in storage in a closet for at least 35 years and there is no sign of warping what so ever. Do any of the readers of this post have an obviously warped bridge from Hills, Wurlitzer, Francais,  Moennig or other first rate shops made before about 1975? It may be that I have only kept those which were really good examples but I honestly don't remember throwing any away. I will take another look at the "violin bridges" site and see if it sheds any light.

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Nathan, one factor may be bridge blank quality. I stopped using Aubert bridges years ago. When I am adjusting the tilt of a violin bridge I expect the feet to leave the top on one side or the other. I notice that many modern blanks will stay flat to the top, and the bridge bend instead. I felt the difference in cutting, too, with treated Auberts having a soggy, unclean crossgrain cut compared with other brands. The other thing I notice is that I am replacing a lot of the treated Aubert bridges that are closing up over the knee on the E side--sagging under the load. I don't know if the problem is wood choice, treatment, or the sum of both. I replaced one yesterday (E gap nearly closed) that according to the date written was cut in 2017 (not by me). So I use other brands. Beyond that, of course the bridge has to be properly cut, but a bad blank is a bad start.

A few years ago I tried to replace a bridge on a Strad cello that had been cut around 1915 by Caressa and Francais. It sounded great, but the C was too low. I tried a variety of blanks over a year or two, but the sound always got worse. What was frustrating to me was that I could feel the difference in blanks in the hand compared with the old one that was both light and stiff, and the Aubert blanks I was using at the time felt completely different--the ancient blank was light and steely, like some bows, and the modern brands were generally too dense.. Some years later I stumbled on a blank that would have worked, purely by accident, but the cello was gone.

Of the major manufacturers, I have been the happiest with Stamm, but it's been a while since I stocked up, and I don't know if that would hold now, there being at least one newcomer, maybe more. I choose blanks completely based on their physical characteristics, not visual, and find that there are many great blanks that don't look the part, and the other way around. The first cut I would take in evaluating a blank would be crossgrain, in the kidney, and I will throw out a blank that doesn't feel right when I'm planing it to thickness.

The things we do, ourselves, would be another discussion, but two things I have noticed is that players will persist in trying to stand a bridge correctly straight that the shop has failed to cut so it stands straight (by which I mean the particular back tilt that works, not literally straight), and this will force a warp. Often players who do straighten their bridges have a really good sense of how it should stand!  And if you cut the back of your bridges dead flat you are absolutely guaranteeing a backwards warp in the future. Both flaws were present in the bridge I replaced yesterday. A third issue I deal with a lot is that many modern shops (not the old ones, generally) believe that a thinner bridge will be louder (which is not true) and so I see many bridges that are around 4mm at the bottom, less than 1.2mm at the top, with no belly on either side--all sorts of failures are built right in, there. I think, however, that this is less critical with cello bridges, from what I can see. 

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1 hour ago, nathan slobodkin said:

Much as I would like to blame this totally on the players I think there are other issues at play. Thinking about this further it strikes me that I really don't see ANY warped bridges from the greatest old shops and despite the very small sample group I think I would occasionally see one if the players (already established to be serial fiddle abusers) were the only factor. I was just looking at a Moennig bridge which had been on a cello in storage in a closet for at least 35 years and there is no sign of warping what so ever. 

Right. If the cello was stored in a closet, no player had a chance to get to it, change strings repeatedly, and consequently cause the bridge to warp!  As has already been said, and as an occasional member of the offending class myself, it's players who are responsible when an $$$ bridge warps, and it doesn't take long at all to start. I once had several Moennig bridges warp on me, mainly due to my own lack of attention.

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The bad news is that if the bridge takes a permanent set beyond a certain point, just straightening up the bridge won't be enough.  I think it has to be caught very early.

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If a bridge is straight and functions well in the instrument is there a reason it should be replaced?  I haven't a clue.  I won't even begin to tell you how old the bridge on my college viola is.....

 

DLB

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2 hours ago, Don Noon said:

The bad news is that if the bridge takes a permanent set beyond a certain point, just straightening up the bridge won't be enough.  I think it has to be caught very early.

I was asked to straighten a cello bridge that was almost folded in half (I'm only exaggerating a little--it was really warped).  Since the student was supposed to play in a few minutes, I put a sweater under the tailpiece, gave the standard disclaimer (we don't want to be responsible for wrecking your cello) and pulled it back into position.  The next week I saw it again, and it was like new.  The student's father had taken it off and steamed it flat.

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The idea is that with a bad enough fixed warp, even if you straighten it up, the string pressure will still be tending to buckle the bridge and it won't straighten out.  Thus the need for off-instrument intervention.

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I have had some success heating bridges and clamping them against a flat surface. If the back was arched originally, clamping the bridge flat will resulting in it springing back to just about the original shape. I don't know how permanent this job is but it's a good trick to have in your bag. Especially if you're maintaining a rental fleet.

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Thanks for replies.

Obviously straightening the bridges after the fact is not a problem although I think they are more likely to bend again. Like wise bridges that are not cut well are not involved in this discussion.

I am interested in Michael D's comment about wood however as I also feel that there are some bridges that really do resist bending more than others. I am still using Aubert blanks and will be hard pressed to change as I would have to buy now for 2024. I also judge bridges by feel and find that many of the #7 and  #16 bridges seem better than the DL or Luxe blanks. It seems to me that in the past few years the DeLuxe blanks are being chosen for fancy ray patterns but have wider grain than I am comfortable with. In general I look for the tightest grain I can find and also drop them on the bench and listen for a higher pitched  note in response. Michaels comment about wanting light and hard sounds like the ideal but difficult to find from today's suppliers.

Does any one have inside knowledge about variety and geographic sources for wood used in the past versus the present? How about methods  of testing blanks in advance for strength? 

Michael I did not understand your comment about "cutting cross grain in the kidney" what exactly are you doing and what does it tell you?

Altvcl,

What time period were the Moennig bridges that warped on you? Anyone have warped bridges from Hill, Caressa or similar high end shops from before 1975?

The question of heat treating, ammonia fuming, rabbit poop stacking etc also interests me and if any one has any comments on those please trot them out.

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10 minutes ago, nathan slobodkin said:

 Anyone have warped bridges from Hill, Caressa or similar high end shops from before 1975?

I have. Any bridge can warp, if it is not maintained at the originally cut angle. Any time there is more pressure on either the front or the back of the foot, a bending force will be present. That's not the entire story, but it is a good part of it.

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One of the things I started doing when I began working for myself was making a gauge that the player could use to help maintain their bridge after I cut a new bridge for them.  That combined with a small amount of time spent educating and coaching how to maintain a bridge so far has resulted straighter bridges and happier clients.  The clients call the gauges “idiot sticks.”

 

I have noticed that I can’t count on ordering Aubert blanks sight unseen anymore, and I’ve needed to switch to other manufacturers unless I can pick in person.

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1 hour ago, nathan slobodkin said:

The question of heat treating, ammonia fuming, rabbit poop stacking etc also interests me and if any one has any comments on those please trot them out.

I heat treat all of my bridges.  The few of us who have experience trying to bend torrefied maple ribs have some idea about how bend-resistant it is, so presumably bridges will be less likely to warp.  I like the color, too.

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Nathan, I mean that when you cut around the kidneys, the locations that are endgrain, like in the waist, I like to see smooth solid wood, not something that crumbles under the knife like styrofoam.

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The bent bridges I've seen always were bent with the cup towards the finger board.  I speculate that the strings and/or the tail cords gradually stretch and retuning the strings causes the top of the bridge to be pulled towards the fingerboard.  This suggests that the choice of string core or  tail cord material might be playing a role in addition to the bridge wood quality.  For example a nylon tail cord with nylon core strings might be more prone to bridge warping than the newer synthetic materials or steel.

 

Maybe in the southern hemisphere they bend towards the tailpiece.

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Bridges bend because they are poor wood, not cut right or not maintained correctly by the player.

Wood is a major factor. If you look at great old long lived  Hill bridges etc they are very hard and have very tight growth of about 0.3mm per year and not much medullary ray to show. Most modern suppliers focus more on spectalular rays than good hardness and texture resulting in so called top grade blanks being mainly rubbish

If I come across a great old bridge that has done great service but has come out of adjustment I will try to restore it and keep it going rather than making a new one

 

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