What kind of glue is used to glue the neck to the body?

[David Schwab]

Thanks guys for the input!

David, I was wondeirng abut using epoxy, or even gorilla glue.

Don't use Gorilla Glue. It sucks. Some people do use other brands of polyurethane glue. I think Elmers Ultimate is the one used.

I bought a small bottle of Gorilla glue to check out. You have to use it when it's fresh.. it absorbs moisture after a while. I tried two small household gluing tasks.. a handle back onto a mug, and a plastic handle onto a metal pot. Both joints failed right away. I wouldn't trust it on a neck! Luthier Mario Proulx uses polyurethane glue on his guitars.

Funky, I'm a bit curious about the joint being too tight. From what I read on various places on the web, a tight neck joint seemed to be the thing to do. I don't know, its all very frustrating to me.

It can't be too tight. You want a very tight joint. Just use more glue next time. And clamp fairly hard to make sure you have a very thin glue joint. Of the Titebond glues, the original is best for lutherie, but I've also used type II. Ken Smith uses type III ... the water proof kind. The problem with II and III is they don't dry as hard as the original, and tend to creep over time.

Type II is actually stronger, but it supposedly creeps more.

Popular Woodworking - The Truth About Polyurethane Glue

And what did they find? Zimmerman says that the joints made by the polyurethane glue failed around 3,510 pounds per square inch (psi) of pressure. Franklin’s Titebond, a popular yellow glue, failed at 3,600 psi. And Titebond II, their exterior-grade outdoor glue, failed at 3,750 psi.

"Polyurethane glues stick well and hold odd materials, but they generally aren’t stronger than yellow glues," Zimmerman says. "Yellow glue makes a bond that is stronger than the wood. So while the polyurethane glue might actually be stronger, it doesn’t matter because the wood will always fail first. It’s not a stronger joint."

Other glue manufacturers disagree. Mark Singer, the founder of Gorilla Glue, says that polyurethane glue is actually stronger than yellow glue when you use it in types of joints other than the one that Franklin International tested. Franklin, he says, used a long grain-to-long grain joint, and that’s a joint where traditional yellow glues already excel. Singer says that the real strength of polyurethane glues is in an end grain-to-end grain joint or an end grain-to-long grain joint, which are two joints where yellow glues have always been lacking.

"Shear strength is not polyurethane glue’s strongest feature," he says. "In end grain-to-end grain the stuff is incredible. It far outperforms (yellow glues) in end grain. If you coat both surfaces with polyurethane glue, I’ve seen it (the glue) migrate 2" into wood."

Some luthiers also swear by hot hide glue, but not the liquid kind from Franklin, unless it's very fresh. I really don't want to use cooked animal parts on my guitars.

You can't go wrong with epoxy. I use either G1 or G2 epoxy, or West System. I've glued entire basses together with G2. After 16+ years they have held up as expected.

I always use epoxy to glue up neck blanks and for gluing fingerboards on.

[David Schwab]

Any luthiers want to verify/deny what I said before about over clamping? I'm curious for some other opinions.

I prefer to use as many clamps as possible and I twist the clamps as tight as I can by hand.

The joint should be so tight you can't slip a piece of paper in there.

[voodoochild]

I'd guess that you clamped out all your glue, too. It seems like your method is great.... though that the dry joint is so tight is a bit of a clue that there might not be enough room. What does the inside of the joint look like?

I've known some people to use white elmer's glue on some joints and it works fine assuming a strong physical fit. I'm not quite that brave though.

voodoo child - I've never heard of those problems with titebond. How common is that?

Bad glue is more common than you would think. I mostly see it when I get re-repairs of someone who used that stuff for gluing acoustic guitar bridges. You see evidence of failure all the time using Titebond, even if the repair was clean. Fresh glue is a must and like I said with hide glue it is guaranteed fresh if you make it. Clamping pressure and fit are just as important. Over clamping will starve the joint and cause it to fail. In regards to Gorilla glue, it's a pain to use IMO. That stuff foams out and makes a mess that is hard to clean. Epoxy is OK if you plan to spray a solid color over the glue joint. Epoxy penetrates into the pores and reaks havick on stains.

[MistaT]

So David, based on your post (above) its sounds like you don't concern yourself too much with over-clamping.

IIRC, the clamping action actually forces the glue into the wood pores. Not that I totally agree, but possibly this is a case of "more is better"?

[David Schwab]

So David, based on your post (above) its sounds like you don't concern yourself too much with over-clamping.

No I don't. If you read the specs from Franklin, they specify:

Required clamping pressure
Enough to bring joints tightly together (generally, 100-150 psi for softwoods, 125-175 psi for medium woods and 175-250 psi for hardwoods)

That's a fair amount of pressure. Using inadequate clamping pressure results in wide glue joints which are not very strong. The glue has good adhesion properties but not good structural cohesion. Glues like epoxy can bridge gaps. Just make sure you have enough glue in the joint so it doesn't all squeeze out.

IIRC, the clamping action actually forces the glue into the wood pores. Not that I totally agree, but possibly this is a case of "more is better"?

What happens is the glue works by penetrating porous materials, and physically locking the surfaces together (covalent bonds) through cross-linking. These glues consist of a polymerizing compound dissolved in water. You wont get a good bond using PVA (white glue) or Aliphatic resin emulsions (yellow glue) if you try and use them on non porous surfaces, like glass or plastic, so clearly they do penetrate the wood before they cross link.

The water in the glue causes it to penetrate the wood, when the polymers cross link you have chemical bonding between the substrates.

Epoxy doesn't even need clamping pressure to work, but you want to keep the joint tight.

[MistaT]

Thanks for the info David!

That was very informative. Thanks!

So now you bring up another question in my mind (man! why does one answer beg another question?)

If water in the glue helps penetrate the wood, then what about slightly dampening the wood joint before applying the glue? Obviously too much water would not be good, but it seems to me that just a bit of dampening of the wood would raise the grain and help the glue penetrate the wood.

Or am I just being a bit excessive here?

[Wakculloch]

Roughing up the surface with sandpaper and any thoughts of gapfilling or dampening will lead to a weak joint. The water will just dilute the glue. The smoother the surfaces, the more perfect a fit, the better.
Forget the glue and concentrate on the wood.

[voodoochild]

Thanks for the info David!

That was very informative. Thanks!

So now you bring up another question in my mind (man! why does one answer beg another question?)

If water in the glue helps penetrate the wood, then what about slightly dampening the wood joint before applying the glue? Obviously too much water would not be good, but it seems to me that just a bit of dampening of the wood would raise the grain and help the glue penetrate the wood.

Or am I just being a bit excessive here?

It is OK to dampen the surface before you glue. I do it with acoustic guitar bridges before I glue them on. Wrap it in wet shop towels and microwave it for 30 seconds or so before I glue and clamp it. Clamping pressure is very important. If you clamp it too hard, you will squeeze out too much glue. When it dries, the water evaporates from it thus causing the joint to draw tighter. You don't want to force that off the bat or the joint is doomed to fail. Not enough pressure will give you a poor joint too. I've learned by feel and experience what the limit should be. You basically clamp it enough til the seams are closed. The drying process will draw it tighter.

[David Schwab]

If water in the glue helps penetrate the wood, then what about slightly dampening the wood joint before applying the glue? Obviously too much water would not be good, but it seems to me that just a bit of dampening of the wood would raise the grain and help the glue penetrate the wood.

Or am I just being a bit excessive here?

I would think it would dilute the glue, or the water would take up space where you want the glue to be. When you use CA or Polyurethane glue on porous surfaces you have to wet them, because those glues don't work well on porous surfaces.

One of the problems with glues like Titebond is the fact that they contain water, so that's why I don't glue my fingerboards on with Titebond.

[Sweetfinger]

When you use CA or Polyurethane glue on porous surfaces you have to wet them, because those glues don't work well on porous surfaces.

CA and Polyurethane(Gorilla) need water to catalyze. That's why you wet a NON porous surface. I've never had any problems with Gorilla glue on porous surfaces. If you're gluing a porous surface with CA, use a thicker glue. Dunno why the joint failed in the OP. Whatever Gibson uses seems to work really well because there's really not much surface area on SG or Les Paul joints. It looks like an epoxy or Polyester to me.

My shop uses Titebond II for about 80% of our jobs and CA for most of the remainder.

[David Schwab]

CA and Polyurethane(Gorilla) need water to catalyze. That's why you wet a NON porous surface. I've never had any problems with Gorilla glue on porous surfaces. If you're gluing a porous surface with CA, use a thicker glue.

When gluing to porous surfaces, the instruction for both CA and Gorilla tell you to wet the surfaces first. You don't have to wet non porous surfaces.

I use quite a lot of CA when building pickups, and never wet anything.

Sometimes you have to use the thin CA, such as wicking into a crack in wood.

My shop uses Titebond II for about 80% of our jobs and CA for most of the remainder.

Why II? It's known to cold creep more than the original Titebond.

Dunno why the joint failed in the OP. Whatever Gibson uses seems to work really well because there's really not much surface area on SG or Les Paul joints. It looks like an epoxy or Polyester to me.

I had an '81 LP and my crazy ex girlfriend decided to throw it from the living room to the kitchen. Luckily when it landed, head first, the glue joint at the neck tenon failed and the neck came off. It wasn't epoxy, that's for sure. I glued it back on with epoxy.

It looked more like a resorcinol- or urea-formaldehyde type of glue.

Gibson says they use Franklin Titebond 50 glue on the neck joints. Titebond 50 They used to use hot hide glue back in the day.

The joint probably failed on the OP's guitar because he either didn't use enough glue, or the glue was old. Titebond has dates on the bottle.

[Sweetfinger]

We use Titebond II simply because that's what the shop was using before I came along and we've never had any problems with it. If it ain't broke .....

[David Schwab]

I've also used it with no problems, because that's what the local hardware store sells, but the people over at MIMF say it's not ideal to use in lutherie.

[Woodenspoke]

Its been awhile since I posted.. man I always love these glue posts on Project Guitar.

Titebond original is the glue to use. Its cheap and all you really need. It is also as strong as epoxy if you wish to look up a Fine Woodworking article on the glue test I am quoting. Almost as strong.

Here are some facts.

Upgrading to a waterproof titebond II or III is a bad Idea, Because it water proof and I have seen it; it can cause issues when direct staining the wood. The symptom is the stain does not penetrate where there many be hidden glue spots under the surface. You cant clean it because it will no longer dissolve with water. I have used this glue but really do I want to spend more money for a glue that may be only marginally better than the original and possibly cause a problem?

Gorilla glue is the worst glue for a guitar (polyurethane) and it is also contrary to its name the worst glue strength wise, and one of the most expensive I may add. I have used it with success on outdoor projects but it does not belong on a guitar.

I have never heard of epoxy creep, use a high end brand like System 3 or West System epoxy rather than some hardware store double tube 5 minute stuff and you will be fine.

Hide glue is great however it requires a bit more commitment than most are willing to provide. Liquid hide glue is just as good without the commitment. If you are building an acoustic I would recommend this glue for an electric it does not really add anything over original titebond.

Adding water to a joint prior to gluing is frankly nonsense unless as stated it is a Polyurethane (gorilla glue) which cures when it comes in contact with moisture. But again dont use this glue or do so at your own peril. PVA or Titebond actually releases moisture to cure so adding water will only prolong the process and dilute the glue as others have mentioned.

epoxy is a love hate for me, one its expensive so I only use it where I feel it does the most good. I use this exclusively for body laminations (Aka Alembic style with many pieces) because it is a chemical cure rather than an evaporative one. try using a half bottle of titebond on a body and you can count the weeks you will be waiting for the glue to setup near the center. Plus it imparts way too much moisture into the body in that quantity. they do make PVA glue for veneer that is thicker but the epoxy will be guaranteed to setup in 24hrs.

As far as glue starvation goes, an easy fix is to wipe on a thin pre coat of PVA and let it dry for 15 minutes. Honestly very few situations in a build require this step except possibly where you use a scarf joint and the end grain on one side of the joint should be sealed or the pores may suck up the moisture too fast.

I hope this helps..

[David Schwab]

Liquid hide glue is just as good without the commitment.

Only if it's a fresh bottle. Always check the date. Same is true with Titebond, but the hide glue goes bad faster.

I don't use hide glue myself.