Almost consistently bad glue joints...

[Darren Rahilly]

Hey gents. So one if the first guitars I made for someone has found its way back to me. I was upset to see that 2 back braces had come loose. (Back material is cherry, bracing is sitka spruce) also, fretboard popped off of neck very cleanly, wasily.(both neck and fretboard are bubinga).the glue i used was titebond original in a gallon size.
The guitar was built in a dirty basement shop, and I wonder if dust and inconsistent temperatures could lead to glue failure. OR if it was me, too much glue, not enough, bad clamping, uneven pressure, etc... ill put some pictures of the glue joints. Just tried, file too large. I'll se what I can do, but I would appreciate any suggestions, as I do not want to go any further with building if I can't trust my glue joints.

[Barry Daniels]

How cold is your basement? How do you prepare your joints before glue up? Any chance that your glue got frozen in the past?

You need to compress your photos below 150 KB to post them. I use an app on my Mac called "Multiple Image Resizer" to compress photos.

[Darren Rahilly]

Thanks Barry. It was always above 55 in the basement. Prepare joints for gluing? Well, i clean up the cuts of dust... thats really it. Not sure if the glue got frozen or not. Its a possibility.
I'm not on a Mac, but ill look into a picture resizer. Thanks for the tip
D

[Barry Daniels]

How much above 55? The best joint are machined within minutes of getting glued. Glue that has been frozen will have a stringy texture and may separate into a watery layer.

Another question is how old is the glue?

[Alain Lambert]

i clean up the cuts of dust...

Surfaces for gluing must be freshly planed not cut

[Darren Rahilly]

The glue wasn't stringy or watery. Freshly planed tone bar bottoms? Ok, got it. How about the underside of the soundboard? Planed? Sanded?
D

[Darren Rahilly]

]Pics

[Barry Daniels]

Your neck looks REALLY rough. Gouges, nicks, and low spots do not glue properly. Need to work on your woodworking skills.

Also, I see areas of heavy build up of glue. A tight joint will almost have no visible glue if the wood surfaces are smooth and flat. Solution is again woodworking skills as well as sufficient clamping.

[Darren Rahilly]

The gouges and nicks came from popping the fretboard off. I've since purchased 12 clamps, I hope that will be enough

[Clay Schaeffer]

What kind of humidity control was used? Inconsistent temperatures often lead to inconsistent humidity levels. If the guitar was glued up in a humid summer basement and moved to a heated low indoor humidity house that could cause glue joints to pop loose.

[Darren Rahilly]

No humidity control. I will look into this, thank you.

[Darren Rahilly]

I've cleaned up the neck and bottom of fretboard, taking care of all the gouges, nicks, and low spots. I've verified that both surfaces are indeed flat, and that the Truss rod sits just below the necks gluing surface. So I'm ready on that front. Does gluing together two different types of wood promote glue pop? As in cherry to sitka spruce? I'm currently doing a pauduk back with sitka bracing, and don't want any surprises down the road...

[Barry Daniels]

Different species of wood can glue together fine.

One thing to be aware of is that when you put a water-based glue like Titebond on the fingerboard, the moisture will quickly soak into the thin piece of wood and cause it to curl up along the edges. This can cause a gap along each edge which seriously compromises the strength of the joint. I see evidence of this in some of your photos.

Two ways to address this;
1) Use a non water-based glue like epoxy.
2) Use a clamping caul that places pressure along each edge. (You are using cauls aren't you?)

In my shop, I use all of the above techniques.

I also advise that you do the glue up in a place that is above 65 degrees F.

[Alan Carruth]

Wood changes dimension much less along the grain than across, so braces that are glued across the back are always under some stress from humidity changes, no matter what the wood. That's probably not your main issue.

Research on glue lines in wood aircraft structures back in WW 2 showed that :
1) surfaces worked within 15 minutes of gluing produce stronger joints, and
2) planed surfaces are better than sanded ones.
Much (if not most) of the strength in the glue line comes from the chemical bond between the glue and the wood. A freshly worked surface will ten to bond better to the glue since exposure to the air allows for chemical reactions that interfere with bonding. A search on 'surface energy' should supply more information.
Cut surfaces made with sharp tools are clean and flat. Sanded surfaces look more like a plowed field, with scratches, loose fibers, and wood particles impeding the wetting action of the glue. Scraped surfaces are somewhere in between; cleaner than sanded ones, but not as nice as cuts made with a sharp plane. A light pass on both surfaces with a sharp scraper, just before gluing, provides a much better surface with almost no change in dimension.

IMO, clamping is used to bring things into alignment, and squeeze out excess glue. Even pressure is more important than heavy pressure, particularly if the parts fit (as they should in this business). I use 'rubbed' joints for some things, with no clamps at all, and have for decades with no problems. You have to pick your battles, of course, but the point is that lots of clamps won't make up for poor fit and technique. As Obi-wan never said:"Spread the force, Luke!". A couple of clamps with good cauls to even out the pressure will be far better in most cases, particularly on thin stuff like tops and backs, where the clamping force doesn't spread far beyond the footprint of the clamp face.

I've never used epoxy for a fretboard that I can remember. The keys with water based glues on those large surfaces are good cauls, as has been said, and leaving the joint in clamps until the water gets out: overnight or longer usually.

We all go through this learning curve at the beginning; don't let it get you down.

[Darren Rahilly]

I have a radius sanding block that I use to radius my fretboard as well as clamping. That goes on top of fretboard. Should I be using something under the clamps on bottom, too? Like a 2x4?
I appreciate your help, thank you
D

[Barry Daniels]

A caul that places pressure along the outside edges of the fretboard is a necessity.

A board with a couple of 1/4" square strips glued along the edges to follow the outline of the fretboard will work.

Or a radius sanding block that is as long as the fretboard will work great. A short radius block is not the thing to use.

[Darren Rahilly]

I have a long one.

[Mark McLean]

Everything that people have said about joint preparation and clamping is important. Titebond is generally a good glue for luthiery but one thing you need to know is that Titebond and all similar glues have a limited lifespan. 1-2 years is the maximum recommended time, then it definitely deteriorates. If you buy it in the large quantities and take a while to use it up you can run into problems. And it may have been sitting on the shelf for a while before you bought it. Titebond has a manufacture date on the label - so at least you can tell when it gets old. But don't worry, one of the good things about this business is that just about everything is repairable (until someone uses epoxy).

[Alan Carruth]

I was told several years ago that museum conservators start their day with a pair of anathemas; one on people who use wood screws to 'repair' antiques, and another on those who use Titebond and the ilk. The problems with Titebond are that it's not really soluble in water, and that nothing sticks to it very well, including itself.

Water will eventually soften Titebond, but by the time it does the wood is likely to have gone to mush. Acetic acid breaks it down more quickly, but it's still not fast. I once got the Titebonded top off a bass using hot photographer's stop bath, which was, iirc, around 30% acetic acid (as opposed to 5% for vinegar), but it took five hours. Acetic acid reacts with iron to form a permanent black stain, although stainless steel usually works OK for separating joints.

After you've gotten the joint apart you have to remove all of the old glue of you aim to get a permanent fix. For well fitted glue joints this means that you'll end up with things being looser than they should be, since it's impossible to get all the glue off mechanically without removing at least some wood.

So I'd put Titebond right down there with epoxy and polyurethane glues in the 'repairability' department.

[Darren Rahilly]

What glue do you prefer for guitar making?