Sunken under bridge feet.


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Artists,

 

The problem is common in old instruments: The top plate wood directly under the bridge feet has been compressed. There may be a post crack and the arching could be deformed, in this case there is no post crack and the arching is OK. The sound post was fit too tight and caused compression on the inside of the top plate, but that is easily corrected as the wood betwean the ff's is thick. The issue is getting the top under the bridge back to a uniform surface. The area will not push out with a cast and heat/sandbag. Weisshaar describes a method of planing the interior of the top plate under the bridge feet to a uniform 1 mm thickness and pushing the area out with a patch. I have corrected minor problems of this nature in the past with filler (sandarc/seedlac) but for those mighty potholes I am hoping someone has the cure that I seek.

 

Regards and thank you, Danny

 

Attached is a snip from Bromptons current auction: lot 116.

post-30450-0-25234100-1394639227_thumb.jpg

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Dear heaven, that doesn't look sunken, it looks deliberately excavated, like someone started an inlay and gave up on it.  IMHO, grain matched inlay of old wood, retouched to invisibility.

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I guess that I'm not enthused about removing any wood from the outside of the top, even to prepare a patch bed. If there was a need to do a patch between the ff's then it could be pushed out. Just leaving it alone is perhaps the most conservative approach, but who wants to buy something with dents in it? I am thinking about all the dents in wood that I have steamed out.

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I've seen a number of very beautiful repairs involving pieces let into the top under the bridge feet - I looked at a Prague Eberle recently that had an exquisite repair of this sort, with each grain line matched and feathered at each end. Apparently this was a trademark repair of FA Homolka.

in extreme cases I think this is the only way, although perversely a historic violin is probably worth more before doing this work than after.

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I wouldn't expect the top of an old violin to have a uniform shape beneath the bridge, although I do see that this is an extreme example.

 

When I learned about plastercasts, and reshaping arching, I was shown to put some gummed paper tape scraps in these depressions before I started, just to preserve them - so that they wouldn't be pressed out and lost. We tore out the little scraps of tape, so that the edges would be soft and irregular.

 

My instinct is to leave well enough alone, unless there's some good structural reason to change things. I've seen good violins terribly damaged by people letting in little patches from above, and I'm sure that over time, there's every chance that these repairs, however well done, will themselves fail, and become unsightly.

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Ummmm, going outside the box, one could tailor a bridge to hide this, and have the feet bottomed with epoxy casts or something taken from an original impression in dental rubber or plaster, then "file to fit and paint to match" so to speak.  You'd certainly never have to worry about it walking :lol:

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How about a 3-d printer made insert...

 

I pressed out a nice fiddle with similar damage. Left a quarter sized patch under each bridge foot, but I wouldn't do it for a customer again. It would have to be something that I owned and had hopes of selling.  Nathan is right, certainly less than 0.5mm, and there is no going back, even after it crumbles away when you try to press it...

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Bothering me is......what caused this? Bad choice of wood? Extreme moisture over time? Maybe, rosin under the bridge feet?

 

Scott

Use of a sawzall to fit the bridge. :)

Actually, if you read the OP, the image is from Bromptons, and is used for illustration.

Petherick blamed cases without enough clearance for the bridge for top dents.

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I would love to hear how Jeffrey or Jerry Pasewicz would handle this.   

 

I have done both ways in the past-- pushed them out from the inside and also added wood from the top.   If this case is as severe as it seems in the picture, I'm not sure it could be pushed out.   

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Bothering me is......what caused this? Bad choice of wood? Extreme moisture over time? Maybe, rosin under the bridge feet?

 

Scott

 

As mentioned the thumbnail is only an example. The actual top that I have on the bench has very a nice tight grain and is light and stiff. The arching is a little "pinched" but the area betwean the ff's is flat. I sawed the neck out after I measured so I don't know what the neck angle was. I do know that the post was way too tight but the plates held up - no cracks. My suspition is a combination of: 1.) post too tight, 2.) neck angle off, 3). bridge feet like bricks, 4). many decades.

 

 

The question, actually how deep are they? 

The area under the bridge is a uniform 3.5 mm. The dent bottoms are at 2.7.

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The question, actually how deep are they? 

That is the question in my mind , also are they dent or removal?In  my small mind,the problem with the idea of expanding dents with steam is that any crushed wood will not have the same support( cellular)as uncrushed ,would there be a stiffener applied after expansion?

   At VSA2012...there was a German ??? fellow on merchant row, with an amazing gizmo laser scanner, that would scan the damage and then use a CNC to reproduce a negative  plug for crazy shapes ...seemingly,impossible to do by hand.worm holes ,missing chunks of edge /button ect , the program also seemed to allow for alignment of matching wood in the XYZ axis' for grain blending.... has anyone used this ..perhaps "expensive" but with the advantage that no original material need be removed,opening  new possibilities along this line. NOT that we should allow the machines to replace the skill to do fine work ...line grain building ect ...Only that as craftsmen and craftswomen, we have a responsibility to use " best possible practice " BPP for short.

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That machine was astonishing.

 

I can't remember the chap's name, but the service he provided seemed really excellent, and not expensive when you considered the time and effort that it would take to do what e did, by hand. I wonder has he a website?

 

I still don't like the idea of putting patches under the bridge.

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I saw something possibly similar this week on "This Old House." They used a 3D laser scanner to map a complex plaster medallion on the ceiling, then used a 3D printer to make a slightly smaller version for another room. Actually, they were going to make a mold from the 3D print to make the final in plaster.

 

I would personally see no reason not to correct the damage on a fiddle this way, whether it had resulted from wear or vandalism. Why would that be worse than doing a sound post patch?

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