Official Luthiers Forum!

Today we did an experiment at the shop after getting out all our different glues from hide glue, epoxy, titebond, CA and some other stuff.

Yesterday, we glued two pieces of Spruce together, clamped and waited. After 24 hours, we tried breaking apart by tension and sheer forces. The CA was stronger than some other typical wood glues.

The CA bond was so strong that the wood split before the glue joint failed, and we tried tension and shear forces to break it apart.

Which got me to thinking, why is it not use it for bracing a guitar top? It would be much easier and faster to work with and because it dries so hard, it would have the great properties of hide glue leaving no rubbery glue joint to dampen vibrations.

So, if you don't want to take off the braces anyway, and you want something that cures very hard, and that is stronger than the wood that is glued, why not use CA? You see, I had problems because of bad batch of hide glue and using the wrong temperature etc., so it can be finicky. If CA has the same hardness, just not the reversibility, wouldn't it be a good alternative for joints you won't want to reverse any way?

I see a lot of posts about not using it, but not the why. I am not talking about doing the entire guitar with superglue, but the Spruce bracing might be fine right?

Certainly not a glue expert by any means but that won't stop me from chiming in

I wouldn't use CA for braces for a couple of reasons. First, I see no reason to stop using hide glue as it is probably the most user friendly glue for this operation and is totally reversible if I decide I want to redo something I messed up. So in that sense, CA is a solution without a problem. I also am trying to get away from CA in general because it is getting more and more irritating to my nose and eyes. I'm not sure it is from repeated exposure or just me getting older. At any rate, I am slowly starting to find other ways to do the things I usually reached for the CA to do. CA would also be more difficult to clean up squeeze out than HHG and wicking in thin CA under braces sounds messy.

Frankly, I'm not convinced that the glue choice is as important as we commonly think. All of the glues we use should produce joints that are stronger than the wood. A properly cared for instrument should not have to worry about conditions that would cause creep (I understand that once they go out in the wild, all bets are off so this really is a concern). I think that a well prepared joint would have so little glue in it that most glues (I would probably exclude epoxies from this statement) are hard enough to not be sound robbing rubbery lines.

For me, the choice is based in how reliable the actual glue is (is it an unkown brand or stored in questionable conditions), how user friendly it is for the application. That is not to say that I don't consider if a particular type of glue may be structurally disadvantaged for a particular application, just that those cases are fewer that you might think. With that in mind, I keep coming back to HHG unless I feel like I'm too slow to get it done in time.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Your argument makes sense, and it really is a solution without a problem, so that's not why I would be using, it is just that I'm curious because I keep reading it is a big no-no for braces, and I cannot figure out why.

CA sucks in sheer, is not reversible...., and when a brace that had a CA joint comes apart the old glue, in this case CA cannot be reactivated and/or added to to repair the brace. Remember serviceability is a bit different than building, we have to work though F holes and sound holes most of the time and don't have the luxury or a perfect world....

A quality guitar with care should be able to out last us.... Part of the reason why it often can out last us is that those who came before us used glues that are serviceable permitting us to protect and support the prior investment of others so that heirloom instruments, often when they sound better than ever too...., can exist by being serviced when need be.

There are builders who use some CA including for bridges on polyester finishes and it works for them since polyester is so very tough and tenacious. And there are folks who have built an entire guitar out of CA to see if they can do it.

I would suggest test marketing an all CA guitar using unserviceable glues and see if you can get more than $99 for it because that's all it's likely worth in our industry so very steeped in tradition....

I'll add that CA has it's requirements too and needs to be fresh, have open times observed, and avoided for applications in sheer.

Lastly when unserviceable glue is used for things like bridges, neck joints, braces, bridge plates much more invasive methods are required to attempt.... to repair the thing.... Examples are cutting the neck off since the glue joint won't release with heat, routing off a bridge, etc.

I built a guitar over three decades ago using CA for almost everything including braces -- still intact today. I think plenty of instant glue is used on the imports. Contrary to common belief CA can be released using heat just like PVA and hide glue. I believe the taboo is associated with traditions rather than science. However, there is a real concern of generating indelible florescent yellow green stains in Spruce and other woods. On the other hand I experienced no advantage using CA versus PVA. I am a fan of Original Titebond.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Mostly I'd worry about the CA working it way through the top and showing itself

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Joe Beaver
Maker of Sawdust

Good way to earn the wrath of all guitar repairmen, Joost.
I am cursing you just because you are considering it.

Too many builders and makers of guitars don't think about repairs after a product leaves the shop or factory. Of course, the same could be said of auto makers, etc.

Use some kind of protein based glue - not CA. THANKS.

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"Act your age, not your shoe size" - Prince

I built a guitar with CA for the tentalones, might have used it for the braces. It was an experimental guitar and I did not use more than about $10 in wood. It turned out to be a favorite of mine. Wish I put a rosette and truss rod in it.

AR and PVA glues don't stick well to old residue either, and people reglue braces with them anyway. Why is CA so much worse? Just because it's more difficult to get apart, incase the instrument ever needs major restoration work in the distant future?

I do agree that protein glue is the best. I use hot hide glue for everything except box closing, where I use Old Brown glue (which is just hot hide glue with urea added to extend open time)

Since you answered your own question, why did you even ask?
Then you mentioned you use protein glues...
Make up your mind, man - don't just argue for the sake of arguing.

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"Act your age, not your shoe size" - Prince

About ten years ago I built a guitar almost entirely out of CA, braces included. The guitar has not exactly been treated well in those years and is still holding up fine. I built it as a sort of experiment. I'll tell ya one thing, gluing braces and blocks together with hand pressure and 30 seconds time is pretty cool.

I don't think I'd use it for bracing, but I did go on a luthier tour of Tom Ribbecke's shop where an assistant was doing just that, gluing in braces with CA. Don't know if he's still doing it though. Might be fun to find out.

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Ken Franklin
clumsy yet persistent
https://www.kenfranklinukulele.com

I have a CA-only guitar on my list of things to try, but only after getting through a lot more building. I will take a look through the archives, Mr. McKenna!

Based on my understanding of the boss's text in the building guide, it looks like reversibility and clean-up of cured adhesive are the two biggies for avoiding CA for structural work...shear strength seems to be something that is not an issue for wood-to-wood bonds where spruce is one of those woods. A pull from the guide (with permission):

Suitability of Various Wood Glues for Guitarbuilding.:

From discussion of cyanoacrylates:

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A constellation only takes shape when one maps the whole.
- Beth Brower

Adhesive selection, in its simplest form, is really a matter of considering the material(s) being bonded and desirable properties for the specific application. For a guitar the material being bonded is almost always wood. Given that the stresses introduced by string tension are effectively negligible (in my experience I have only seen a modern PVA completely fail the 150F sheer strength test under ASTM D-905 once), so as long as we're talking about adhesives that can retain 50% or more of their room temperature strength at 150F creep will simply not enter the equation. So that narrows our options to *good* PVA wood glues (these should all be "yellow" glues of which Titebond I, II, the Extend series, Gorilla wood glue, and Elmer's carpenter's products with the exception of those with Type I water resistance), Hot Hide Glue, Epoxy, and good CA's (to my knowledge there is still only one maker of CA in North America (so additives are not required to survive containerization from China like 99% of CA on the market, which improves performance since it will ideally make an acrylic polymer when cured, *do not use activators unless absolutely necessary* even acidic wood species will allow them to cure but more slowly... If you must, consider wiping the surface with ammonia to neutralize the pH or make it a little basic).

What else should we consider... Maintenance, perhaps? Is this a mass production situation, where repair means throw out the old one and ship a new instrument because it isn't worth the time required to fix? (Use whatever you want, CA can do the job) Or is it of sufficient quality that it could be an heirloom and always worth repairing? (In which case we want something that can be disassembled with relative ease). Let's go with that case, this is the Luthiers Forum after all. CA *can* be melted and reversed with heat and dissolved with solvents such as acetone, and it will definitely not be the high point of your day. Water resistant glues aren't as strong as traditional resin modified PVA and don't match their high temperature performance (which correlates with creep), Titebond Extend is my weapon of choice. It has plenty of assembly time, retains 85%-90% of its bond strength at 150F, and it can be steamed apart. If you have a vacuum press complete with a heated platen and a spare block of dry wood you can achieve remarkably short press cycles (RF is even more awesome but not exactly standard kit in a luthier's shop). Hot Hide Glue is also great stuff, with the only real downside of convenience because it needs to be prepared and kept at temperature while you use it. I will gladly put a good HHG joint up against the best modern PVA any day of the week. The higher the gram strength the better, but it comes at the expense of higher gel points and therefore shorter assembly times. My personal choice is 250 gram, because it's pretty much the sweet spot in terms of balance. A solution of Aluminum Chloride can be brushed/misted over the joint to protect it from humidity. It steams apart beautifully, and although I advise cleaning up excess HHG from parts prior to re-gluing it is not absolutely necessary. The only special precaution is to avoid excessive clamp pressure, because HHG is susceptible to starved joints unlike PVAs.

I can keep going, but most folks around here are pretty sharp, so I'm more inclined to answer any questions about what I've said above.

There must be a story to that Fred. How many times did you stick yourself to the guitar?

I agree with what's been said about the disadvantages of CA for braces. I also have some more particular reasons for using CA as little as I can.

When I first started to build guitars, I used a lot more CA than I do now. I tend to want to do things quickly, in bursts of enthusiasm, and CA seemed fast. I discovered that doing things quickly in bursts of enthusiasm resulted in my constantly making errors. Fixing errors took exponentially more time than doing it slowly and correctly in the first place. I've had to retrain myself to plod ahead carefully, constantly double-checking. I still make errors, but most errors made with fish glue or hide glue are easy to fix.

For example--if I'm gluing a brace and the go bar pushes it a little out of position, with CA it's likely to be instantly glued in the wrong position. With slower glues I just push it back into position and readjust the go bar. Sometimes I put little guide blocks, held with go bars, to make sure the braces are in the right position. CA would seep, gluing my braces to the blocks and my blocks to the top or back. With fish glue, my favorite for this purpose, I have plenty of time to get everything positioned correctly and then clean up the glue. For me, it makes for a better job, and a much more pleasant experience since I don't have to rush.

As someone who is still learning, I make some mistakes even though I take my time. So for me the person who may have to deal with the glue joint isn't some unknown repair person decades from now, it's me, tomorrow, realizing I made another dufus move and need to take the #5&% thing apart and do it again. CA melts when heated, and you can scrape it off and re-glue, but it's a lot easier to deal with protein glues.

The capillary action of CA can be a help sometimes, but it also seems to go where I didn't expect it to go; in contrast, the behavior of hide and fish glues are easy me to predict. I also find that protein glues are cheaper, have a much longer shelf life, and are easy to wash out of clothing.

In the right hands, CA can be made to work for almost any purpose. I still keep some around, but as time goes on, the less I use of it, the happier I am.

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Tim Allen
"Never hurry, never rest."