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Please forgive my rookie knowledge and status but am REALLY perplexed by a recent observation. I have only built a single Martin Jumbo kit and went through all the growing pains of a first guitar but one thing I THOUGHT I nailed was the bridge placement. I measured, re-measured, tested, taped, screwed, double checked, re-measured and was thrilled by how exact the bridge location appeared when I was done.

Now here is where it gets weird. I looked at the bridge the other day and noticed a small bare area of wood that was SUPPOSED to be under the bridge. I thought no way did I miss that. Then I noticed the finish in front of the bridge was wrinkled a bit as if the bridge had slid forward and wrinkled the finish. THEN I took the strings off and noticed the hole that I used as crew in to align the bridge was now offset just that same little bit.

OK, so here goes, is it possible for a bridge to move? I used LMI white glue and the guitar is about 3 weeks old. I COULD have missed all the effort and measuring and stuff that I did to insure the bridge's location but I need to know if anyone has ever experienced this sort of thing?





LarryH38725.4835648148

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It happens all the time with PVAs, but not usually this fast unless it was
subject to heat.

It looks to me like the glue joint had to be bad to begin with. Is your glue
fresh? Could it have been a starved joint? That would be quite unusual
with a PVA unless it was way overclamped with too little glue to begin
with.

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Hi Larry;
It looks to me like your glue joint is about to fail. Believe me, yours is not the first. What kind of clamp(s) did you use?
Did you get a nice even line of squeezout all around the bridge? Did you leave the clamps on overnight at least?
A bridge joint can fail due to over or underclamping... Too much, or too little glue in the joint... Masking tape residue (if you masked out the bridge area before spraying)... It looks like the area was well scraped, but a thin layer of finish left on the top will cause failures too. And probably other reasons I haven't thought of.
I know it's a bummer, but (IMHO) your best bet is to remove the bridge, clean everything up, check the fit & try again. If you wait until the bridge pops off, it can make the problem worse by pulling up chunks of top where the glue is still holding.
If the little bits of your guitar in the pics are any indication, it looks like you did a beautiful job. Don't let this minor setback discourage you!
Good luck with the fix.
Dan'l

GREAT FORUM!

[QUOTE=Daniel M] Hi Larry;
It looks to me like your glue joint is about to fail. Believe me, yours is not the first. What kind of clamp(s) did you use?[/quote]

I used 2 screws through the 1st and 6th pre-drilled holes into a caul that was double sided taped to the bridge plate to position the bridge and then 2 C clamps across the middle section of the bridge.


[quote]Did you get a nice even line of squeezout all around the bridge? Did you leave the clamps on overnight at least?[/quote]

Yes and yes.

[quote]A bridge joint can fail due to over or underclamping... Too much, or too little glue in the joint... Masking tape residue (if you masked out the bridge area before spraying)... It looks like the area was well scraped, but a thin layer of finish left on the top will cause failures too. And probably other reasons I haven't thought of.
I know it's a bummer, but (IMHO) your best bet is to remove the bridge, clean everything up, check the fit & try again. If you wait until the bridge pops off, it can make the problem worse by pulling up chunks of top where the glue is still holding.
If the little bits of your guitar in the pics are any indication, it looks like you did a beautiful job. Don't let this minor setback discourage you!
Good luck with the fix.
Dan'l
[/QUOTE]

Thanks so much for the advice

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[QUOTE=David Collins] It happens all the time with PVAs, but not usually this fast unless it was
subject to heat.

It looks to me like the glue joint had to be bad to begin with. Is your glue
fresh? Could it have been a starved joint? That would be quite unusual
with a PVA unless it was way overclamped with too little glue to begin
with.[/QUOTE]

Thanks David, Yes the glue was fresh and yes it could have been a starved joint but not from lack of glue as I put on gobs just from inexperience.

I have a feeling there might have been some finish residue left on.

Now I need the technique to remove the bridge using LMI glue. Should I post a separate thread?

Larry

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Cut your bridge shape out of a thin piece of cardboard and cover it with
aluminum foil (shiny side up). Make sure the mask is tight around the
bridge to protect the finish. Then give it three to four minutes under a
heat lamp at very close range and the glue should soften nicely. I would
anticipate that LMI's glue should soften with heat the same as any other
PVA.

I doubt it was a starved joint if you used 2 screws to clamp it. You would
have had to put very thin glue and clamped the hell out of it. I think if
anything you may have left too thick of a glue layer. If all you're using is
screws through the pin holes to clamp you really have to make sure the fit
is perfect before gluing. You should be able to set the bridge on the top
and not see any gaps, or a slight amount in the center that comes
together with light pressure if anything.

Then spread an appropriate but not overly generous layer of glue. The
two screw clamping method may not provide enough pressure to squeeze
out all of the excess glue if it is to thick. Your bridge may have been
floating on a layer of dried adhesive.

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Sounds like a case of too much glue, not enough clamping. With PVA glue especially, if there's a layer left, it will creep much sooner.

Hide glue folks, the answer is always fresh, hot hide glue <g>

But this isn't bad at all, and you'll gain experience removing a bridge! Look to the bright side, always.

Larry, you might want to get some clamps out at the wings of the bridge as well, from the sounds of your setup, there was nothing clamping the wings down.

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Thanks for all the feedback. Got the bridge off but it wasn't so pretty. The foil mask idea was awesome but I'm not sure the glue ever really softened much from the heat lamp. It finally popped off with just a little damage to the top (small dent). The joint looked OK if there is any way to judge these things. But I did see some rosewood left behind in the glue so the glue was harder than the rose wood in places.

Anyway got it re-glued but have an impossible time telling if there was too much glue as Mario has suggested or too little - though if anything there may be too much (again?) - sorry I didn't read Mario's advice before beginning the repair. I'll leave it clamped for a couple days and unstrung for a couple more because that is not something I want to do again.

It seems to have gone over-looked from a previous post but I did have 2 C clamps that I used along with the screws and those both went on each wing as suggested, just noticed I said those 2 clamps were on the middle, but they clamp(ed) the wings.

Again thanks so much for the help. This time if it moves I'll know that it did indeed move, instead of my imagination and this time it will be because of too much glue and not too little.LarryH38725.7830208333

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I was looking for the Hide Glue suggestion and agree with Mario and a host of others to use it on this critical joint.

I guess it started soaking into my brain reading Frets.com years ago. I use HHG on two critical joints, neck dovetails and bridges. Why, PVA creep, and reversibility. The hide glue vs. polyvinylacetate test Frank performed in his household oven convinced me.

One good fridge compressor from the dump, a bit of vinyl tubing a vacuum guage & a homemade copy of LMI's bridge clamp & you're set up for the easiest & quickest way I know of gluing down a bridge. (How can you tell I just built a vacuum setup & I'm in love with the rig?!)

Larry,

Lately I have been hearing more and more people with problems with LMI glue. I am wondering if they got a bad batch. Doud Kliest glued a ceadr top with some he recently purchased and all looked well until it was all braced and the seem just split open. He further claimed the glued lokked 'chalky' when dried, usually an indication to me that it has been frozen. So all I am saying is that it may not have been your problem at all but the glue. Still, I agree with Mario and Bruce...Hot Hide glue. I sell the same stuff that Frank Ford recommends and you find all of the use instruction on Frets website and Sylvan Wells little hot pot idea that he explains on his website is the way I go. Oh ya, I have also moved to syringes to apply the glue. I cna let ya know which ones I use and how if you are interested.

Shane

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Which ones Shane?

Shane brings up another interesting point. PVA glue is NOT freeze/thaw
stable. This is why I would never order any PVA glue that has to be
shipped in the winter. Even the stuff in hardware stores comes in an truck
that is not climate controlled, so I used to buy enough in the fall to last
through the winter (always checking the date code).

In any case, I agree that a PVA's are not a first choice for bridge joints.
And Larry, if it didn't come off cleanly it probably means you didn't get it
hot enough. The bridge will typically be smoking and bubbling resins
when it gets hot enough. When PVA reaches the right temp it will have the
consistancy of a thick silly putty.

I still would like to know what is different about thier glue. There is no
PVA based adhesive that I have ever known that will have a sour smell
when it expires. This sounds more like a natural glue than a synthetic
adhesive, but they advertise it as a PVA. David Collins38725.8447106481

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Syringe? Don't they melt? I have some from giving pet shots, they are only a quarter at the Co-op.

Well as you have read I'm back into LMI glue for the same bridge joint. If it creeps again I'll CERTAINLY not use it again and my first inclination is to blame my technique, not the glue. If it turns out to be the glue I will be BUMMED. I live in San Diego and it can get chilly but never freezing so I wouldn't expect that to be a problem, since LMI ships from NorCal.

Hide glue is a real stretch for a first a first guitar but if that's all that will hold down the bridge (how is that possible?) I'll reluctantly jump in.

The problem I'm facing is that it seemed to take a couple of weeks for the bridge to move, so no matter how long I leave it clamped, short of those couple of weeks there's nothing I can do but wait. That's a crap feeling looking over the guitar every time I pick it up to see if there is any movement. At least I KNOW where the bridge is now and can measure even the slightest movement.

Thanks again for all the help. I'll follow up either way.

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Pictures Daniel, pictures! (It's like posting a thousand words in this tiny space!!)

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It's late in the game, but I'll say that it sounds to me like too thick a glue line, if anything. If the glue had frozen it would more likely have simply popped. I've seen bridges slide like that on 'affordable' guitars that give every evidence of insufficient clamping pressure on other joints. I also re-topped a 70's Martin once that had the neck shift up when the top split along both sides of the fingerboard, and the 'popsicle brace' and shoulder brace joints just slid. The inside of the top looked like it had been smoothed off with a garden rake, so there was no way they could have gotten the glue line thin enough.

The water that they sit in is only 145 degrees Bruce. I have a friend that I am building a flamenco guitar for and he gave me a bunch of, get this, anal sac syringes. They are absolutley GREAT! They have a curved tip and the opening is exactly perfect for laying down the perfect bead and you have great control, depress the syringe and the glue flows, stop, the flow stops, so there is very little mess. I tried a brush and small glue bottles and neither was satisfactory to me.

Shane

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Hey Larry if this is any comfort, I am on my first also and am using hide glue. I just figured that if this was the way I wanted to go down the road why not just get at it right from the start? It is intimidating when you read and think about it but when you get at it it is really not hard to use at all!

Shane

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Thanks for the tip Shane

Serge

I agree re heating of LMI. I have heated pieces to separate and the glue stays ridged until you reach the right temp. and the pieces easily come apart.

[QUOTE=Shane Neifer] Hey Larry if this is any comfort, I am on my first also and am using hide glue. I just figured that if this was the way I wanted to go down the road why not just get at it right from the start? It is intimidating when you read and think about it but when you get at it it is really not hard to use at all!

Shane[/QUOTE]

Very encouraging as usual, but I am intimidated by a 30 second working time, unless I read that wrong in another thread. It simply takes me much longer than that to set up my clamps. I'll put hide glue on my list of upgrades, maybe for my next kit that's on its way.

Thanks

Larry

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The only time I have used LMI glue was about a year and a half ago. I glued 3 tops and 3 backs together with it. All of the joints failed. I know a lot of people use it and like it, and I may have got a bad batch, but I'm not willing to take the chance. I use HHG for everything but gluing the tops and backs on with. Titebond there.

Larry, if the working time of hide glue intimidates you should consider trying fish glue. I've been testing and using and Norland high tack fish glue for a number of years now and have every bit of faith that it equals hide glue in cured properties. The big difference is that the collagens don't gel until about 8-10 celcius, as opposed to hide glue's 35. That means it is liquid at room temperature.

It does require a longer clamping time, and is said to have lower water resistance but higher heat resistance compared to hide glue. You can buy it by the gallon (which doesn't quite meet thier minimum order) direct from Norland, or Lee Valley tools repackages it and sells it in smaller quantities.

I'm really quite surprised this glue hasn't gained more popularity in our trade. It took a good deal of time and research to earn my trust, but it has become my glue of choice for most work.

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