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Other than the fact that you can't ever dissolve it, why would one not use like 5 minute epoxy in some applications: like regluing a bridge or a brace, or gluing in a fretboard? THX

People use epoxy for gluing down fretboards all the time, its a great way, it does not intruce moisture to the neck. Bridges, I dont know?

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Lance@LuthiersForum.com

That would be (introduce)

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Lance@LuthiersForum.com

What Lance said.

I would not use 5 minute epoxy though instead using something with a longer open time providing more time for the epoxy to penetrate the wood and grab better.

Although controversial (here on the OLF....) I am in the camp that believes that all epoxies are not created equally.  Much of the stuff that is available many places, Devcon, Lock-Tite, etc. for example is not anything that I would ever use.  I often see these brands hanging in the supermarket check-out line next to the chap-stick and M&Ms........

Instead go with a quality epoxy such as West systems and rest a little easier that you won't be needing to redo the job later.

Also, I don't like the idea of using epoxy for bridges.  The glue joint/interface between the bridge and the top is pretty darn important in that this joint does not inhibit the free flow of vibration.

Properly applied epoxy, wetting both surfaces, adding a thickened center layer, and clamping makes for a fairly thick glue joint when compared to say HHG.

Do some tests putting a blob of epoxy, HHG, Fish glue, and Titebond or LMI on some scrap, wait a week, then chisel each blob off.  You will find that the HHg and Fish glue dry more crystalline and hard, Titebond and LMI will be second, and epoxy will remain a tab rubbery.

lastly, in order for a bridge glue joint to efficiently transfer vibration the glue joint needs to be very thin on a molecular level.  HHG is perhaps the very best choice for this and I hear good things about Fish glue in this application too.

[EDIT]  That should read a "tad" rubbery....

Dennis my apologies because I missed perhaps the most important part of your question.  And that is why, if you need to reglue a bridge, the original glue joint failed.  My long winded comparison of various glues in this application was addressing the symptom and not the cause of your woes.

Do you sand the bridge on the top of the guitar in the position that it will live and radius the bottom of the bridge to the guitar top's dome?  This is the best way to ensure a proper fit and complete wood-to-wood contact.  It also helps to very lightly scrape the bottom of the bridge just prior, with-in 15 minutes, of gluing too.

[QUOTE=drusso] Other than the fact that you can't ever dissolve it, why would one not use like 5 minute epoxy in some applications: like regluing a bridge or a brace, or gluing in a fretboard? THX[/QUOTE]

Reversibility, taking apart a joint glued with epoxy is almost impossible without damaging the parts.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

[Quote=laurent]Reversibility, taking apart a joint glued with epoxy is almost impossible without damaging the parts.[/QUOTE]
I have used a heat blanket to remove an epoxy-glued fretboard. The joint came apart fairly easily with no damage to either part.

The Smith "All Wood" epoxy that LMI sells dries rock-hard IF you mix it properly. Agree with Hesh that the 5 minute stuff never seems to fully harden and stays rubbery. I have used it to glue in rosettes and end grafts but would never use it on a structurally important joint.

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In Markham,Virginia

Epoxy is not what we look at as a conventional glue on guitars. Yes some may be reversible via heat but again , not all epoxies are the same and when you look at instruments , often you have to consider the future and what has to be removed in the future. Bridges are at some point may need to come off.
   I only use epoxy for truss rods.
john hall
blues creek guitars

[QUOTE=JNixon]I have used a heat blanket to remove an epoxy-glued fretboard. The joint came apart fairly easily with no damage to either part.[/QUOTE]

I've had a very different experience, and with heat blankets as well. I think gluing bridge or braces with epoxy is a great risk for the future of the instrument, and repairability (is that a word?). Not only I am convinced that wood parts will easily get damaged, especially softer woods, but the finish will definitely suffer with the heat required to separate the parts. Just my 2?.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

I want to add that some cheaper guitars had an epoxied neck/body joint and anybody trying to reset a neck on those is up for trouble. In the end probably sawing the neck off and reassemble it with bolts.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

I think that most of us who use epoxies in guitar construction and pore filling use it sparingly for very specific glue joints.   I use WEST epoxy for laminating necks, gluing on fingerboards, and doing multi-laminate peghead overlays.   These are all joints which are sensitive to moisture balance in the wood and where using water based glues can cause a lot of stress problems as the induced moisture from the glue escapes the parts glued up.

Each and every glue joint in a guitar should be looked at as a separate issue from all others.   For some parts, HHG or fish glue may be best; for others it may be LMI white glue; for yet others it could be a polyurethane glue; for celluloid bindings it may be Duco cement; and then there's good old CA superglue.   Some joints should be reversable, some should not be, and guitars, with their typical bindings, are not made to be disassembled in the same way that violins are.   

I use up to seven different glues in putting guitars together:

Hot hide glue: top and back seam, top bracing, back bracing

LMI white glue: Linings and kerfings, end blocks, top and back to sides, wood or fiber bindings

Franklin's polyurethane: Pre-laminating back of peghead overlays, front peghead overlay

WEST Epoxy: neck laminations, fingerboard, pore filling

Thin CA: frets, some inlays, ab purflings

Medium CA: nut, gap fill, sometimes bridge to polyester finish

Duco: celluloid bindings

Each glue is chosen for it's own properties for a particular glue joint. Yes, there may be other choices for each, but over the years I've gotten it down to what I think is best for each application.

Awesome information Rick. Great post. Thanks.

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Any epoxy worth using as an adhesive should never cure rubbery.  If it does, something got mixed wrong.

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I like to say i have used Devcon and Loctite and have never experienced rubbery joints or joint failure. If mixed right these epoxies work well.

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Guitars, guitars and more guitars.

I have read that shafting epoxy (the stuff used to repair golf clubs) works very well and can be "undone" using heat methods like those for hide or PVA glues. 

Well I had a friend that built a Martin Kit. and had a hard time fitting the dovetail. In frustration he shimmed the best he could then epoxied the neck in. Later he discovered he set the neck plane for way too "LOW" at the bridge. He cane to me and we steamed the joint loose. It took longer than a PVA or Hide joint would have but it did come out without damage. It took a lot of clean up to get joint ready for glue-up

Anyway my point is that epoxy can be steamed and heated to separate. No it not as convenient as hhg or Titebond but is doable. More so than you might think.

I don't use it for any structural joint in my guitars. But ask yourself how many times in the life of a guitar is the fretboard removed. Not a common thing. So if there is a joint where epoxy could be a good reasonable adhesive I think the fretboard to neck joint would be it.

And I agree with Hesh there is a world of difference in epoxies. you convenience store 5 min. epoxies tend to be a lesser grade base that is more susceptible to UV degradation and often will not harden well and stay some what soft and gummy. High end or professional grade epoxies tend to be a bit touchy on the A/B ratios but in the long rune make a better alternative.

"Anyway my point is that epoxy can be steamed and heated to separate. No it not as convenient as hhg or Titebond but is doable. More so than you might think. "

I'd be very careful before making such a blanket statement about "epoxy".   There are many epoxies that can handle 250 F temperatures without failing.    The term "epoxy" is being bandied about here as though it was a well defined term...like "wood".

Good point Rick but I think most of us understood that we are talking the commonly used epoxies in lutherie. Heck there are epoxies good to 500f. I have not worked with any other epoxies that Paces General use 15 min, 5 min and finishing resin as well as hardwarestore 5 min, West System and System III. All those seem to soften between 150-220f.

However your right! My blanket statement was presumptuous.