Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by Denny, Jul 8, 2008.
......to attach set necks?
Modern factories use PVA, though traditionally it was hide glue (which some small shops still choose).
Which is strongest? which will take coloring? what about Tight-bond? Gorilla glue (don't laugh - that stuff is strong)?
"Which glue is strongest" is kind of like "which guitar is best". There is no universal "best" or "strongest". Hot hide glue and PVA are both perfectly and equally appropriate for the job. PVA glues like Titebond (Original, not Titebond II or III) or Elmer's Carpenter's Glue are readily available to anyone and work just fine. Larger factories will typically use white PVA's without the yellow tint like Titebond, but in the end they're pretty much the same thing.
Polyurethane glues like Gorilla Glue are not appropriate, as they offer no end advantage over traditional glues in a good mortise and tenon joint, they're messy, they can stain, and they come with the distinct disadvantage of being unserviceable.
I've seen an Epiphone Junior ($99 bolt-on SG) with the neck gorilla glued on.
It had foamed out around the joint. It has been stable for a few years (my friend owns it).
Hide glue can be tinted. Frank Ford has some good articles about hide glue on his site:
There is more good information out across the web. We got into it doing violin repairs, and it truly is the best glue for some (not all!) instrument work. Use the right tool for the job.
Yea Gorilla glue foams out big time. I THINK, if I'm not mistaken, the directions say to moisten the wood with water before applying the goo - this is supposed to cut down on the foaming. - It is very strong though. Very interesting artilcles BTW! thanks
Polyurethane glues actually rely on moisture for curing. In woods dried to 4%-6% moisture content as we often use, there is simply not enough moisture in the wood to quickly catalyze the glue, hence the need for adding water.
In guitars it is used by some for things like making laminate necks, but that's one of the only places it has gained acceptance. Any joint such as fingerboard, neck joint, bridges, braces, rims, etc., is more important to be left serviceable.
As to coloring, that brings up other questions. If you're referring to accepting stain around a joint after assembly, yes, PVA and hide are both good for this. If you're talking about tinting the glue before assembly, there shouldn't be any need for this. Pretty much every glue except epoxy (and to some extent cyanoacrylates) require a tight wood-to-wood joint to create a decent bond, so there should not be much concern about stainability to begin with. With the exception of the area immediately around the glue joint that may be saturated with glue, there really should be no solid line of glue to stain anyway - if there were, that part of the joint wouldn't be structurally sound.
So a good tight joint with PVA or hide will accept stain fine, though most guitar companies layer the colors in with the finish today.
I've watched 2 different builders glue set-necks with Titebond.
I myself have used Titebond to repair broken necks.
Stuff works great!
I'm building some Vox Phantom-type bodies and contemplating making a set-neck one - should be interesting. I'm trying a very different neck/body joint than the standard and will let you guys know AFTER I see how it works (don't want to make a total fool of myself LOL) . I'll probablly use Tite-bond.
tite-bond is my workhorse woodworking glue and I don't hesitate to use in on guitars. Look for the original, plain-old, Tite-bond which has a red label. There are other forumulations that are blue or green with roman numerals II and III, which you'd only use if you're making outdoor projects. The original red-label Titebond has better workability in that it doesn't run when you brush it on, and it will be possible for some luthier generations from now to steam the joint apart of the neck angle needs to be reset - can't do that with the waterproof Titebond II or III.
I agree with the other posters about Gorilla Glue - stay away from any polyurethane glue for guitar work - it's too much of a mess and testing in one of the woodworking magazines this past year suggested that for most woods it isn't any stronger than yellow PVA. Incidentally, white PVA like Elmer's school glue is okay but it has a longer set time and longer open time - you would only need that if it's a very complicated assembly with lots of parts that need to have glue applied before putting them together. So go with yellow PVA and the brand I'd recommend is Titebond.
Keep in mind that Titebond creeps really bad and no matter how many times you tell a customer not to leave their guitar in a hot car, it just goes in one ear and out the other. I prefer using hide glue as it is much more heat and creep resistant. On el cheapo's I might use Titebond and I regularly use it for bracing, top/side/back cracks. For fingerboards, bridges, necks, and other high tension areas I recommend hide glue only. Not the liquid stuff you can buy at the hardware store either. That stuff is limited with its uses.
frank ford says the same thing.
here's what titebond looks like after it's been in a hot car.
Assuming a glued joint may need to be taken apart deliberately, Titebond liquid hide glue is probably the best choice over almost any other off-the-shelf glue. There was a site that demonstrated the results of gluing two pieces of wood together using different glues, and heating the wood in an oven; Titebond hide glue beat them all in heat resistance and overall strength.
?? if you're referring to this, titebond failed the test and real hot hide glue passed; liquid hide glue wasn't mentioned.
Titebond liquid hide glue is essentially conventional hide glue with about 20% urea added to lower the gel temp. It has it's place, but has a very short shelf life, and is not the same as (nor for many applications as good as) conventional hot hide glue.
As for serviceability, PVA glues, hide glue (conventional hot or compromised Titebond liquid), fish glue, isinglass, are all equally reversible, though the natural glues provide for better future reglues. Even epoxy and cyanoacrylates are reversible with heat. Glues like polyurethane (like Gorilla glue), urea formaldehyde, and resorcinol adhesives can be extremely strong and provide excellent moisture and heat resistance, but are not serviceable.
I was interested to see that McNaught uses 2 part epoxy on his neck joints
A repair shop used what might have been a stale bottle of liquid hide glue and the reset neck crept right off the body of my archtop. Hot hide glue isn't going to do that, but you have to be equipped for it.