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How to glue a bridge thats lifting?
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Author:  Matthew Jenkins [ Mon Jul 14, 2008 5:25 am ]
Post subject:  How to glue a bridge thats lifting?
Hi
I built a guitar for a friend and the bridge has started to lift in the corner!!
The bottom of the bridge was radiused to fit the dome of the top. I'm hoping that I just didn't put enough glue on originally!
I don't have a heating iron and I would really rather not attempt to lift the bridge.
What would you recommend for re-gluing and how??
I originally used titebond.
Many thanks
- Mat
Author:  Sam Price [ Mon Jul 14, 2008 6:05 am ]
Post subject:  Re: How to glue a bridge thats lifting?
It may indicate bridge failure further down the line.

If that was me, I'd apply heat to the bridge to soften the joint, remove the bridge, clean the glueing faces thoroughly, and re-do all the processes (like for example, matching the bridge glueing face to match radius of top)

Most premature bridge "lifting" stems from incorrect clamping...analyse how you clamped it last time, make sure the cauls fit perfectly.

It's OK to use Titebond again, as long as those glueing faces are clean.

I use AR glue myself (same type of glue as Titebond, but the stuff I use is whiter with longer open joint time), and would like to try HHG one day..a lot of the pro luthiers on this forum use it.
Author:  Matthew Jenkins [ Mon Jul 14, 2008 6:22 am ]
Post subject:  Re: How to glue a bridge thats lifting?
Thanks Sam
I was really hoping not to have to take the bridge off.
However, is there a way of doing it without having to buy a specific tool?
Thanks
Mat
Author:  Hesh [ Mon Jul 14, 2008 6:22 am ]
Post subject:  Re: How to glue a bridge thats lifting?
Mat buddy the only proper way to reglue a bridge is to remove it first, clean it up, the guitar top too, check the fit and reglue. Some of the things that you might do to just tack down the lifting corner would make it more difficult to repair later and the bridge could very well lift other places.

Here is a link to a toot/discussion on removing and regluing bridges.

http://luthiersforum.3element.com/forum/forum_posts.asp?TID=11038&KW=tutorial#forumTop%22
Author:  Matthew Jenkins [ Mon Jul 14, 2008 6:25 am ]
Post subject:  Re: How to glue a bridge thats lifting?
Thanks Hesh
Author:  David Collins [ Mon Jul 14, 2008 8:19 am ]
Post subject:  Re: How to glue a bridge thats lifting?
As Hesh said, there's no quick fix. To properly reglue the bridge, it needs to be fully removed, cleaned, and refit. I just finished up a bridge and bridge plate replacement on a '42 Banner SJ, and was planning on posting some pics of that job later today which includes a slightly different style of bridge removal. However you get it off though, it still has to come off.
Author:  Howard Klepper [ Mon Jul 14, 2008 12:47 pm ]
Post subject:  Re: How to glue a bridge thats lifting?
It has to be removed to be reglued. But does it need regluing? You haven't given enough information to decide that. Not every lifting corner has to be reglued immediately. Which corner? How far in can you slip a piece of paper? Got photo?
Author:  joe white [ Mon Jul 14, 2008 2:11 pm ]
Post subject:  Re: How to glue a bridge thats lifting?
Howard Klepper wrote:
It has to be removed to be reglued. But does it need regluing? You haven't given enough information to decide that. Not every lifting corner has to be reglued immediately. Which corner? How far in can you slip a piece of paper? Got photo?


Exactly! Did the guitar swell? Over humidified? Bringing it back to proper RH could settle the corner.
Author:  Matthew Jenkins [ Mon Jul 14, 2008 2:30 pm ]
Post subject:  Re: How to glue a bridge thats lifting?
Thanks guys
When I wrote this post I was really hoping for a 'quick fix' (you'd think I would've learnt by now!). The bridge definitely needs removing. You could definitely see daylight where the corner of the bridge came unstuck from the body!!!
I was really worried about removing it because I just don't have the correct tools. This evening the guy I built the guitar for took it to a luthier who lives around the corner from him. The luthier said that it was an easy fix and that it happens sometimes and doesn't reflect the guitar build itself.
Obviously i'm going to pay for the repair but it is a little embarrasing!
Thankfully the person I built it for is a friend and he still loves the guitar. I just hope nothing else goes wrong [headinwall]
Thanks again for your replies
- Mat
Author:  Flori F. [ Mon Jul 14, 2008 2:34 pm ]
Post subject:  Re: How to glue a bridge thats lifting?
Well, it may be that we've had two weeks straight of 70% humidity, but I've got the same dang problem.

Here're pictures. Thoughts/advice appreciated.

http://bp2.blogger.com/_jimCSw8cXX0/SHupgH5JAJI/AAAAAAAAAG8/C7Scb6quZTk/s1600-h/bridge1.jpg

http://bp0.blogger.com/_jimCSw8cXX0/SHupgfbCTmI/AAAAAAAAAHE/zqnupDPj-b8/s1600-h/bridge2.jpg

http://bp1.blogger.com/_jimCSw8cXX0/SHupggsGn0I/AAAAAAAAAHM/mQv4aWZn1_k/s1600-h/bridge3.jpg

Sorry...couldn't get the pictures to upload as attachments, then couldn't figure out the image function...
Author:  Sam Price [ Mon Jul 14, 2008 2:54 pm ]
Post subject:  Re: How to glue a bridge thats lifting?
Flori, that looks like the bridge is going to pop off soon...

A hot summer's day will finish off the job of the bridge coming off completely....

Is there finish under the bridge? Meaning, did you sand off the finish to bare soundboard where the bridge was going to be glued?
Author:  Flori F. [ Mon Jul 14, 2008 2:59 pm ]
Post subject:  Re: How to glue a bridge thats lifting?
Failure...ugh.

I fear I didn't manage to sand all the way through the french polish beneath the bridge.

I'm learning way too much about repair.

I guess the good news is that if there's still some finish under there, it'll melt quickly...

There's a bright side, right? [headinwall]
Author:  Sam Price [ Mon Jul 14, 2008 3:07 pm ]
Post subject:  Re: How to glue a bridge thats lifting?
mffinla wrote:
Failure...ugh.

I fear I didn't manage to sand all the way through the french polish beneath the bridge.

I'm learning way too much about repair.

I guess the good news is that if there's still some finish under there, it'll melt quickly...

There's a bright side, right? [headinwall]


Most glues need a CLEAN wood to wood contact for a successful joint.

When you remove the bridge, mask tape around the bridge "foot print" and sand off the finish in that area, right through to the bare wood. You might have to change paper often, because shellac can clog up the paper.

The underside of the bridge needs to be as clean as a whistle too (I use a cabinet scraper). After removing the masking tape from the soundboard, place a piece of FLAT sandpaper (I use 180 ) where the bridge is going to go, and sand the bottom of the bridge, making sure the bridge doesn't "roll", so that the bottom of the bridge matches the curvature of the guitar top.

I think dear Hesh has posted a tutorial about this somewhere, lemmee have a look to see if it's still kicking around, back in a mo...
Author:  Sam Price [ Mon Jul 14, 2008 3:11 pm ]
Post subject:  Re: How to glue a bridge thats lifting?
viewtopic.php?f=10102&t=15008&p=214949

Scroll down to about halfway to Hesh's post (Posted: 20 Dec 2007 04:42)

I've used this technique on my guitars and it's great.
Author:  Flori F. [ Mon Jul 14, 2008 3:15 pm ]
Post subject:  Re: How to glue a bridge thats lifting?
I'll follow Hesh's method. Thanks for the tip.
Author:  Sam Price [ Mon Jul 14, 2008 3:31 pm ]
Post subject:  Re: How to glue a bridge thats lifting?
There are also issues with the humidity too..keep it around 40% RH whe gluing cross-grain joints...

Here's a checklist I personally use when gluing on the bridge...
1) make sure the RH is at the right levels.
2) Sand the underside of the bridge glue face to match the radius of the guitar's top.
3) make sure cauls are made correctly for both the underside & the top of where the clamps will go....a dry run of clamping will determine this. The clamps have to grip & sit firmly to both the underside and above..sometimes you can tighten those clamps and think they are OK...then they slip...
4) Clean wood dust off EVERYTHING...the entire guitar top, the worksurface, the bridge, the bridge footprint on the soundboard, I wipe the gluing faces with a slightly damp cloth and let dry before applying glue.
5) Apply the glue and spread out with the fingers so that the entire bridge joint face is covered with an even layer...in this case, not "dripping" off..
6) Clamp, clean up squeeze-out & pray... ;)
Author:  Barry Daniels [ Mon Jul 14, 2008 3:42 pm ]
Post subject:  Re: How to glue a bridge thats lifting?
I have removed a lot of bridges with nothing more than a putty knife. Work in in slowly and make sure you are not digging into the grain of the top.
Author:  Hesh [ Mon Jul 14, 2008 4:45 pm ]
Post subject:  Re: How to glue a bridge thats lifting?
Flori buddy a couple of observations:

You mentioned that there is still finish there. Was the finish removed under the bridge prior to gluing it on? If the finish has not been removed from the entire bridge foot print that could be part of what caused this. Also what glue did you use?

Was the bridge radiused to the top by sanding it on the top in stable RH prior to gluing?

It looks like the saddle is very high, any reason for this? The torque loads on the bridge are pretty high with the saddle this high. I like to see 1/2" of height from the bottom of the low E string to the guitar top at the leading edge of the bridge.
Author:  Flori F. [ Mon Jul 14, 2008 11:03 pm ]
Post subject:  Re: How to glue a bridge thats lifting?
Thanks for the insights all. I think my trouble may have been threefold.

One, I was paranoid about scraping away too much finish and ruining my french polish hard work, so I wasn't as diligent as I should have been at the very edges of the bridge footprint. Two, I probably wasn't diligent enough about wood dust. And three, I didn't radius the bottom of the bridge at all - just glued it on (with Titebond).

Hesh, I'll measure the saddle when I get home. It probably is high & also a contributing factor.

Barry, I'll try a putty knife & add heat if necessary. Since I removed the fingerboard from the body 3 times (and re-glued), I've got a little practice using the knife.

Seriously, I'm feeling like a major f-up. It's more than mildly depressing. I'll be going to a local luthier hat-in-hand tomorrow, begging for a little mentoring.
Author:  Flori F. [ Tue Jul 15, 2008 12:56 am ]
Post subject:  Re: How to glue a bridge thats lifting?
Took the bridge off. I'd left a little finish under the bridge in the corner that lifted. Everywhere else was still firmly attached.
Author:  Matthew Jenkins [ Tue Jul 15, 2008 2:11 am ]
Post subject:  Re: How to glue a bridge thats lifting?
Hey Flori
I'm sorry we live so far away from one another. I would've gladly shared a bottle of 'red' with you. I think we both need it!!
- Mat
Author:  Hesh [ Tue Jul 15, 2008 7:43 am ]
Post subject:  Re: How to glue a bridge thats lifting?
Flori don't feel bad I did all of the things that you did, or didn't do, on my first too. It happens to many of us but it also is an opportunity to learn to remove and reglue a bridge..... :D

Perhaps this might help - think of the bridge as yet another brace for the top only one of the most important braces. As such it needs to be glued on as well or better than any brace. This means a perfect fit and wood-to-wood contact everywhere. In addition how one clamps the bridge on can be a problem area too. Just like when clamping a brace a bridge needs to have fairly uniform and complete clamping over it's entire span and foot print.

Congrats on getting the bridge off - see it was not that bad once you have done it.
Author:  Flori F. [ Tue Jul 15, 2008 9:20 am ]
Post subject:  Re: How to glue a bridge thats lifting?
Hesh wrote:
Congrats on getting the bridge off - see it was not that bad once you have done it.


Ha! It is that bad! Little bit of tear out. Mark Geiger may roll his eyes and/or smack me when I show it to him today.

Mat, I could still use that bottle! And it's 7am.
Author:  Sam Price [ Tue Jul 15, 2008 10:33 am ]
Post subject:  Re: How to glue a bridge thats lifting?
Lutherie in the early days is a rollercoaster ride of extreme highs and lows... :mrgreen:
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