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| Bridge gluing problems http://luthiersforum.com/forum/viewtopic.php?f=10101&t=39713 |
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| Author: | F.D Guitars [ Thu Mar 14, 2013 9:20 am ] |
| Post subject: | Bridge gluing problems |
Hi! I'm having problems for my ebony bridges keeping glued to a red cedar tops, after about 6 months they came unglued (titebond), never have that problem on my spruce tops  .My first problem was on the first guitar i build, so, i think it was an inexperience issue, but got the same trouble on one of my latest one!! Any idea or suggestion? Thnx!!! |
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| Author: | Tom West [ Thu Mar 14, 2013 9:29 am ] |
| Post subject: | Re: Bridge gluing problems |
Do you score around your bridge when removing finish. WRC not as strong as spruce and tends to peel easier. Were there wood fibers on the Bridge. Tom |
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| Author: | F.D Guitars [ Thu Mar 14, 2013 9:58 am ] |
| Post subject: | Re: Bridge gluing problems |
I make some scratching before gluing, to improve grip, at least i think it works fine with spruce  . No finish, i set the bridge, mask location and them spray finish. Lots of work to remove finish later...  . The bridge was relatively clean of fibers, mainly was more unglued than ripped off.Thanks Tom! |
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| Author: | Tom West [ Thu Mar 14, 2013 10:15 am ] |
| Post subject: | Re: Bridge gluing problems |
I wonder if the ebony bridges are quarted or flat sawn. Flat sawn can tend to distort from water based glue. Have you checked the flatness of the width of the bridge? Other then that I'm not sure. Tom |
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| Author: | Fred Tellier [ Thu Mar 14, 2013 10:18 am ] |
| Post subject: | Re: Bridge gluing problems |
Is there ceder and glue on the bridge or is there glue on the top and not the bridge? Fred |
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| Author: | Greg B [ Thu Mar 14, 2013 1:22 pm ] |
| Post subject: | Re: Bridge gluing problems |
I've heard of this happening before when people mask the top where the bridge will be glued. It may have something to do with the adhesive residue. Another thing that could cause a problem is polishing compound worked into the bare wood. At any rate, the lack of fibers stuck to the bridge indicates a technique failure. Any wood surface should be scraped or sanded and cleaned immediately before gluing. Simple exposure to air will reduce the surface's affinity for wetting. The book "The New Science of Strong Materials or Why You Don't Fall through the Floor" by JE Gordon has a pretty good section on gluing. I can't recommend it highly enough. It should be required reading for all luthiers. http://www.amazon.com/Science-Materials ... 0691125481 |
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| Author: | B. Howard [ Thu Mar 14, 2013 3:22 pm ] |
| Post subject: | Re: Bridge gluing problems |
Cedar can be fairly oily and pose problems with glues and finishes. I always clean with a solvent to remove the oils before gluing or finishing. |
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| Author: | guitarjtb [ Thu Mar 14, 2013 3:47 pm ] |
| Post subject: | Re: Bridge gluing problems |
I have glued bridges on 30 new guitars and way more than that on repairs and restorations. I have had only 2 glue failures, and both were on cedar tops with ebony bridges. I think the problem on the first one was lack of glue. The 2nd one, not sure. I have glued ebony on spruce since then, but have not use cedar on any other guitars. |
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| Author: | Blain [ Thu Mar 14, 2013 8:45 pm ] |
| Post subject: | Re: Bridge gluing problems |
B. Howard wrote: Cedar can be fairly oily and pose problems with glues and finishes. I always clean with a solvent to remove the oils before gluing or finishing. Yep. When I toured Collings Guitars, I remember them saying that they don't do Cedar Tops because of too many Bridges coming loose because of the oil in the Cedar. Now obviously it can be done, you should just take extra care to make sure it's good and clean before gluing up. |
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| Author: | Link Van Cleave [ Fri Mar 15, 2013 12:22 am ] |
| Post subject: | Re: Bridge gluing problems |
F.D Guitars wrote: I make some scratching before gluing, to improve grip, at least i think it works fine with spruce Thanks Tom! That works fine if you want a large glue line, less wood to wood contact and a weaker joint. Ideal is a clean smooth freshly milled joint surface that fits as closely as possible. L. |
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| Author: | Ken Jones [ Fri Mar 15, 2013 12:39 am ] |
| Post subject: | Re: Bridge gluing problems |
I agree with Link, the cleaner and tighter, the better. That said, cedar tops are notoriously fickle about keeping hold of their bridge. Makes one really question the wisdom of pinless bridges on cedar tops ala Breedlove or Lowden. |
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| Author: | guitarguitar [ Fri Mar 15, 2013 7:52 am ] |
| Post subject: | Re: Bridge gluing problems |
Real Important, Leave the bridge clamped up for 2 days before you pull the cauls off on cedar, redwood. Skip |
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| Author: | A.Hix [ Fri Mar 15, 2013 9:09 am ] |
| Post subject: | Re: Bridge gluing problems |
Something that I always do is put a thin coat of glue on both the bridge and the top, let it sit for a few minutes, rub it with your finger, making sure the glue is evenly spread, add a bit more, then clamp the bridge to the top. This gives the glue more time to wick into the wood fibers before it gets squeezed out from clamping. Also, dont clamp TOO tightly, you dont want to squeeze all of your glue out. I have made over 40 guitars with no bridge failures... not to say it will not happen at some point, just no problems yet. I have one of my early guitars, it is 15 years old, and the bridge is still nice and tight. |
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| Author: | F.D Guitars [ Fri Mar 15, 2013 9:27 am ] |
| Post subject: | Re: Bridge gluing problems |
Well, the reason it's unknown for me, but i guess it's more reated to wood than to procedures, never got a bridge fail on spruce.. maybe that oil, i'll try some solvent to clean up before gluing and wait about 6 months to see it fail and try another solution....  Thanks you all! |
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| Author: | Greg B [ Fri Mar 15, 2013 11:52 am ] |
| Post subject: | Re: Bridge gluing problems |
I'd venture a guess that the OP omitted one of the steps mentioned in this thread, and may well be thinking  right now...If one were to pull the masking tape, and then buff, the simple act of buffing will burnish the cell walls of the bare wood closed, making a weak glue joint unavoidable. Before gluing bridges, my method is to sand the surfaces with stearated paper (3m gold), wipe with a damp cloth to clear the dust, and warm with a hair dryer to dry. I suspect the detergent in the sandpaper helps a bit to clear any surface oils. I know some people poo poo the idea, but I agree that applying glue to both surfaces is important for the strongest possible bond. It helps ensure that both surfaces are maximally wetted. |
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