Fish glue for Cocobolo?

Construction and repair of Classical Guitar and related instruments

Fish glue for Cocobolo?

Postby Robert England » Tue May 01, 2012 12:53 am

I am considering making a guitar with Cocobolo back and sides for a client who wants one. I have read that you need to either use Epoxy glue for all the Cocobolo joints, or else wipe the joints thoroughly with acetone before gluing. However, today I was talking with another local luthier who has built many steel string guitars with Cocobolo, and he told me that fish glue works fine on Cocobolo, provided that the joint is freshly sanded or scraped before gluing. He said that the acetone approach is a real P.I.T.A. because you have to clean the wood over and over until there is no more color coming off onto your rag. Fish glue sounds like a much more convenient method. I assume that if any guitar was going to come apart due to weak bonds, it would be a steel string before a classical, due to the obvious higher string tension, and probably rougher handling the guitar might be subjected to.

Has anyone had any experience, successful or otherwise, gluing Cocobolo with fish glue, or any other alternative glue than Epoxy?

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Re: Fish glue for Cocobolo?

Postby Waddy Thomson » Tue May 01, 2012 2:03 am

I have one in the works now, but the last one I did, I used HHG for the back joint - no problems. It's 3 years old now. The only break I had was along a grain line, which I fixed with Epoxy. without issue. It did not break along the glue line. Always work with a fresh joint with Cocobolo. Acetone just dilutes the oils and brings more to the surface, faster. I'm trying to remember, but I believe I sanded the joint with 120 grit on a level before gluing. The glue up should be done within 10 to 15 minutes of the fresh joint. Read a thread over on OLF earlier today, one of the experienced builders said he's used HHG, Fish, Titebond, LMI White, Probond, and Epoxy all without issue.

Here's mine - was my #5

P1040298 (Medium).JPG
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Re: Fish glue for Cocobolo?

Postby Robert England » Tue May 01, 2012 2:30 am

Looks nice, Waddy! Thanks.
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Re: Fish glue for Cocobolo?

Postby Marcus Dominelli » Tue May 01, 2012 4:16 am

I've glued several cocobolo bridges with hide glue and they're holding strong, but I de-oiled the surface of the cocobolo until in had lost most of its color to ensure the glue would adhere well.
I cannot think of a reason why using fish glue would not require the same de-oiling treatment as hide glue or titebond. In fact, the prudent thing is to de-oil all types of rosewood, even Indian rw before gluing, unless you're using c.a glue or a type of epoxy formulated for oily woods.
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Re: Fish glue for Cocobolo?

Postby Danijel Kralj » Tue May 01, 2012 5:41 am

How do you do it Marcus ?
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Re: Fish glue for Cocobolo?

Postby Marcus Dominelli » Tue May 01, 2012 4:29 pm

Just rub the rosewood area to be glued with a clean rag that has been soaked in either actetone or alcohol. Keep cleaning the surface using clean parts of the rag until no more oil is coming out of the wood. Some rosewoods have a lot less oil than others. You'll notice the surface of the rosewood has lost a lot of it's nice colour where it has been de-oiled.

I read about one luthier years ago who used to soak his bridges in a can of acetone until all the oil leached out. I'm sure it works, but it's totally overkill and a waste of solvent. You just need to de-oil the surface being glued.
The only place where it's a hassle is where the linings get glued to the sides; it can take a bit of time if the sides are really oily like cocobolo. But skipping this step, as many luthiers do, is really just going to shorten the useable life of the guitar.

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Re: Fish glue for Cocobolo?

Postby Alexandru Marian » Tue May 01, 2012 5:26 pm

I never handled cocobolo, or any other noticeably oily wood, but the one thing that I think it is crucial for a good bond is to cut, scrape (or sand as the last resort) the wood just before gluing. I made a lot of tests and older, oxidized surfaces do not bond well. Fish is better perhaps because it dries slowly but with hide, you can just peel the joints open with no wood failure even with spruce-on-spruce. Pay special attention to the bridge!!!
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Re: Fish glue for Cocobolo?

Postby Waddy Thomson » Tue May 01, 2012 6:54 pm

4 of my first five guitars had Cocobolo bridges. I never de-oiled any of them. All still holding fine. HHG gluing after a fresh scrape with a scraper, then glued within 5 minutes of the scraping. All still holding fine. Longest is 4 years, so far, and that one's been exposed to the worst conditions, as I play that guitar outdoors in October and November, rain or shine. Got so wet one year, I had to retire it for 6 weeks and dry it out. Bridge still tight.
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Re: Fish glue for Cocobolo?

Postby Alexandru Marian » Tue May 01, 2012 7:25 pm

All my bridges are going strong too, plus some steel string repairs. I wonder what is the failure time frame :) I have seen several guitars made by another luthier, white glue, lifting or completely off bridges, made in the 2001 - 2007 frame. Not sure if his glue brand was bad or what. I've also seen some older white glue (factory) guitars where the glue time turned brittle resulting in separating braces, lining and bindings. Call me a snob or whatever, but I definitively believe natural glues are superior.
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Re: Fish glue for Cocobolo?

Postby Waddy Thomson » Tue May 01, 2012 8:13 pm

I believe it's often a fit issue. I've seen some that when they came off, they weren't even close to, in my definition, a good fit. Could be old glue, I suppose, too.
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Re: Fish glue for Cocobolo?

Postby Robert England » Tue May 01, 2012 9:02 pm

Is there a difference between the glue bond between rosewood-to-rosewood joins and rosewood-to-softwood joins? I can't think of a joint in a standard classical guitar design that is rosewood-to-rosewood which isn't also backup up by a rosewood-to-softwood joint. I wonder if the types of wood being joined makes a difference.
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Re: Fish glue for Cocobolo?

Postby Alexandru Marian » Tue May 01, 2012 9:10 pm

I would guess too that the different type of wood and grain directions make for problems. For example look at a strip-less rosewood back or a spruce top joint, if it was glued well you will never see even a witness line in the lacquer let alone a fail (and I am sure that if the joint is well made, the softwood backing or the center fan brace is superfluous)

But the various mixes in the rosette and purflings can create witness marks in the lacquer no matter how tight you make them.
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Re: Fish glue for Cocobolo?

Postby Marcus Dominelli » Wed May 02, 2012 12:43 am

Waddy Thomson wrote:4 of my first five guitars had Cocobolo bridges. I never de-oiled any of them. All still holding fine. HHG gluing after a fresh scrape with a scraper, then glued within 5 minutes of the scraping. All still holding fine.


Hi Waddy. That's good to hear that they're still hanging on there. It's a testament to the strength of hide glue and your attention to getting a good fit between bridge and soundboard.
But do you feel confident that 4 guitar bridges glued in this fashion is enough of a track record to conclude that gluing them without de-oiling the rosewood is going to be adequate for the long haul, considering the kinds of conditions guitars are often exposed to?

I'm always surprised at how many self taught makers don't de-oil the rosewood before gluing. I'll even bet you that most factories do not de-oil. They probably don't want to take the time. In the Bogdonavich book, does'nt he mention that de-oiling is standard procedure?

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Re: Fish glue for Cocobolo?

Postby Waddy Thomson » Wed May 02, 2012 2:25 am

I know that de-oiling rosewoods is a popular method of joint prep, but I have read many other articles and posts by experienced builders that have emphasized the fresh joint vs the de-oiling. My theory and that of a few others I've read, is that de-oiling with acetone or other solvents actually thins the oil and encourages additional bleeding at the point of wiping after the fact. However, I have no proof. And no, 4 bridges is no proof, but it's a representative sample of an inexperienced builder that can glue a Cocobolo bridge to a Spruce top without wiping the oil off the Coco., and it'll stick! :D
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Re: Fish glue for Cocobolo?

Postby Marcus Dominelli » Wed May 02, 2012 2:47 am

Waddy Thomson wrote:I know that de-oiling rosewoods is a popular method of joint prep, but I have read many other articles and posts by experienced builders that have emphasized the fresh joint vs the de-oiling. My theory and that of a few others I've read, is that de-oiling with acetone or other solvents actually thins the oil and encourages additional bleeding at the point of wiping after the fact.


You may be right about this. I think if one is going to wipe the wood with acetone or alcohol it's best to go all the way until the surface is clearly de-oiled and nothing is getting on the rag anymore. But a couple of quick rubs with solvent might actually make it worse like you suggest.
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