Bridge popped off!

[Keith Hustler]

So I am sitting eating breakfast this morning.....pop....from the other side of the room.

The bridge on this brand new baritone came loose.  This is a brand new guitar and I have never had one of my bridges come loose before.  I use regular titebond for gluing my bridges.

You can see in the photo, the glue stuck to the ebony.  But it let go on the spruce top.  I scrap the tops after finishing and before I glue up the bridge.  Maybe I did not get all the finish off before I glued up.

Any ideas out there?  Why this guitar and not any of the others?

[Thomas James]

Old glue?

[Robbie Collins]

Maybe you need to fit the bridge to the top's radius?  Is that a crack showing in the rosette?

[Keith Hustler]

Good comments. I will check the old glue idea. And yes I do radius the bridge Robbie. But that's a good thing to check as well.

[nathan clark]

The joint looks a little starved. Did you use enough glue? Have you considered using hide glue?

That looks like a pickguard on the rosette, not a crack.

[Hesh Breakstone]

Sheesh... can't even get through breakfast without some guitar giving you a hard time.... ;)

Titebond is date coded and I was always keen to not use it if it was more than a year old.  It also can cold creep and before anyone disagrees we have seen plenty of examples of bridges glued on with Titebond that started plowing the finish on the leading edge of the bridge.  Mind you it's great glue but I prefer HHG and just had to stop being the wussy that I was about getting my clamps in place quickly enough and then HHG was a pleasure to use.

So yeah it could be old glue, the joint does look a bit light on residue too but most of all the absence of more fibers on the bridge bottom tells the story for me.

What ever, old glue, too little glue, not enough consistent and uniform clamping the bridge bottom tells the story that the bridge and top did not bond well.  But we knew that.

Step one for me would be to carefully inspect inside the guitar to make sure that the X brace and other braces that define the top dome/shape are not loose.  We often see loose bridges and at times part of the cause is the the underlying bracing structure is not firmly in place.  If the top shape is a moving target in the sense that it's not braced well bridges can give.

When I glue on a bridge I dry clamp everything in place first and check carefully all around the perimeter with a .0015" feeler gauge to make sure that the bridge is indeed down everywhere.  

It looks like you cut the finish back well and even though this is how countless factory guitars have had their bridges glued on we also believe that this idea of having the bridge "span" the ledge where the finish is with no associated rebate in the bridge itself is also why countless factory instruments have their bridges come loose in time.  Where the bridge bottom spans the finish ledge and depending on the thickness of the finish there can be no real wood-to-wood contact at the point of the finish ledge and for some distance inward too.  Again this is how it's done most of the time but sometimes it's just not good enough and some of the factors that can dictate where more wood-to-wood contact is desirable are the size of the foot print itself, the application and resulting tension on the bridge (how much tension an instrument places on the bridge by it's nature, i.e. 12 string, tenor with a very small bridge, etc.).

It looks like the finish is well cleared but I really can't tell and if there is anything else on the top such as shellac, sizing, etc. and it was not freshly scraped through that layer too that can be a problem too.

The joint does look a bit dry to me but I am also not a fan of the idea that a dry joint is all that possible with glues beyond epoxy.    The glue layer does look uniform on the bridge bottom.

So thinking out loud here and sharing what's happening in my pathetic brain, pardon me please.... ;)

Perhaps refit the bridge, clean up the mating surfaces, dry clamp and check the fit and modify accordingly until the fit is perfect.  If the top has a radius and the bridge does not radius the bridge and there is a short tutorial on fitting bridges on my site if you are interested.  Get some new Titebond but before you do Google "Titebond date codes" and be armed with the translation when you purchase your new Titebond so you can tell how long it's been on the shelf at the store.

How you clamp too can be a factor, how many clamps, where the clamping is applied, etc.  I had a bridge shape myself that did not fit the bridge clamping caul well and when I tightened the clamps it actually raised the back edge of the bridge upward - not good.  This is when I began to learn how to geglue a bridge...;)

Although likely not related that crack that was mentioned is problematic in my mind too.  In my neck of the woods I have three humidifiers running 24/7 because it's below freezing outside now and the furnace is drying out the house.  Wood moves, an understatement..., and cracks happen when something has to give.

Anyway hopefully something here is helpful to you.  This stuff happens and happened to me on a early guitar too.  What resulted was that I learned that bridges really require some pretty precise methods for gluing and none of this stuff is hard but it can take a bit of time to get it right.

As to why this guitar and no others.  Do you have a feeler gauge that is about .0015" or less thick?  Check out the others with the feeler gauge and see if any others are getting uppty.

PS:  When I talk about HHG I mean the real stuff and not that awful Franklin bottled stuff....

[Keith Hustler]

Lots of great comments.  Thank you everyone.

Based on all your comments I have had another look this morning.  I looks to me like I did not clean off the finish well enough before I glued up. (lazy?)  The photo shows pretty good fiber pull-off all the way out to the wings, BUT you can see in the photo there is an area the treble side where no spruce fibers came up.  Pretty flat and clean all around the pin holes and all the way to the back of the bridge.  That whole area has no spruce fibers pulled off.

So I will clean it all up, buy some new glue, and try it again.  This time I will be more careful to clean up ALL the finish under the bridge.  Thanks for the comments.

[Alain Moisan]

Hi Keith,

That last pictures tells a bit more.  How thick is your finish?   From the picture it looks thick to me.  Titebond is more forgiving than HHG when you don't have a perfect wood to wood contact, but you might have asked a bit too much out of it.  You might want to cut an inset around the bridge perimiter a tad larger than the finish line left under the bridge, this way you will have a better wood-to-wood contact.

[Frank Ford]

Can't say for sure without having it in hand, but it looks just like the Titebond never had a good chance to wet the surface of the spruce.  Any residual finish will cause the kind of problem you had, and it doesn't need to be much residual finish. After removing finish, I make a habit of using a tiny block and sanding the spruce across the grain with 150 grit or so to make dead certain there's no finish left. 

By way of illustration, here's an anecdote.  Years ago, one of the guys at the Collings factory decided to save the company a few bucks by not changing the router bit on the usual schedule, trying to get more instruments done with each bit.  As a result, when he routed the finish off the top, the dull bit started to have a tendency to "glaze" the surface of the spruce, so the aliphatic glue wouldn't wet it so well.  Fast forward a few months, and they were regluing bridges under warranty.   Since we were qualified to do the work, we reglued at least one of those, and it looked just like yours.

I've seen quite a few just like this - it's just one of the things that happen just to confirm or test our sense of humor. 

[Donald A. Fortune]

Hi Keith-- for what ever it's worth-- I always use acetone on an ebony bridge before I glue it to the top of the guitar,

that way you are fairly sure to have less oils in the ebony before it gets fastened to the top.

just another two cents on your delimia..

best to you on figuering out what to do .. (excuse my bad spelling but it was never one of my strong points)

Peace, Donald

[William F.Eden]

If I am building a new Guitar I always put a lite pencil mark around the bridge axactly were the bridge is going to sit before I ever start to put any sort of finish on, Then I mask it with two layers of masking tape 1/16th inside of the pencil mark. Then I rub the mark off with a soft eracer. When I have all the finish on then I just take an exacto knife and mark it around the eage of the tape and strip it off .Then you just take some terpentine and remove the stiky stuff off were the tape was.    For the 1\16th of finish that is still left under the bridge I just lightly router a about 3/32ds in from the eadge of the bottom of the bridge so the bridge will come in full contect with the Spruce top.Once you put your glue on you will put a little extra on around the eadge that you routered and it will seal it all around the bridgeBill...........