Luthiers: Finish Sinking at Center Seam...
Sept 27, 2024 20:18:32 GMT -5
drlj, Dub, and 1 more like this
Post by amanajoe on Sept 27, 2024 20:18:32 GMT -5
Howard,
Hate to break it to you, but that most likely is a crack, you just don't know it yet. If you put a very bright light in the guitar, you will like see it clearly. More often than not, these "center seam separations" are actually a crack running immediately next to the center seam. Since it has happened in the same place to two different guitars, I'm going to bet it is a combination of a thin responsive top and a heavy bridge plate that is growing and shrinking in a 90 degree direction to the top. (Not that it isn't completely normal to have the bridge be at 90 degrees to the top, just something that is a little different than normal in the way it is moving compared to the top).
First and foremost, H&D should and most likely will take care of it.
Second, the standard procedure is to get some glue into the crack (typically hot hide or to match what the guitar was made with) then to over-hydrate to get the wood to expand and close the crack.
Once the crack is closed, small diamonds of matching wood to the top are glued at 90 degree angles.
The wood is allowed to return to normal humidity levels.
As to leveling the lacquer finish, almost any repair person will tell you matching a lacquer (especially one that has aged for a while) is virtually futile. Many have actually doped in clear cyanoacrylate in small amounts to build back to level and then polish. In such small areas, it is invisible and will not shrink again. Many purists will argue this point and it is obvious H&D got it done the last time, so you could always ask how they did it.
Hate to break it to you, but that most likely is a crack, you just don't know it yet. If you put a very bright light in the guitar, you will like see it clearly. More often than not, these "center seam separations" are actually a crack running immediately next to the center seam. Since it has happened in the same place to two different guitars, I'm going to bet it is a combination of a thin responsive top and a heavy bridge plate that is growing and shrinking in a 90 degree direction to the top. (Not that it isn't completely normal to have the bridge be at 90 degrees to the top, just something that is a little different than normal in the way it is moving compared to the top).
First and foremost, H&D should and most likely will take care of it.
Second, the standard procedure is to get some glue into the crack (typically hot hide or to match what the guitar was made with) then to over-hydrate to get the wood to expand and close the crack.
Once the crack is closed, small diamonds of matching wood to the top are glued at 90 degree angles.
The wood is allowed to return to normal humidity levels.
As to leveling the lacquer finish, almost any repair person will tell you matching a lacquer (especially one that has aged for a while) is virtually futile. Many have actually doped in clear cyanoacrylate in small amounts to build back to level and then polish. In such small areas, it is invisible and will not shrink again. Many purists will argue this point and it is obvious H&D got it done the last time, so you could always ask how they did it.
I'm not saying that incorrect humidity is the problem, but you can watch Dan Erlewine do a similar repair:
Martin pickquards are notorious for pulling apart the seam between the soundhole and the bridge when they shrink.
