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I have had trouble glueing cocobolo in the past & decided to try Kremer's fish glue on my next project. Before going ahead with gluing up the back braces, I did a little comparative test & thought you folks might be interested in my results.
With freshly sanded spruce brace stock & lightly sanded scraps of cocobolo, I applied 4 different glues & clamped them in the go-bar deck for 24 hours.
This morning I pried of the braces with a crescent wrench & observed how the joint failed.
In all cases, the spruce failed, leaving the glue joint intact.
With a sharp chisel I set to shaving the remaining spruce off of the coco.
The results were interesting & (so far) I'm sold on the fish glue.
Elmers aliphatic resin glue held up well & getting the spruce off cleanly was a chore.
Same with the Lepage "yellow glue"
The Milligan & Higgins 192 gram weight hide glue was somewhat easier to chisel off without damaging the cocobolo.
The fish glue however was very difficult to separate from the coco. I chiseled from both directions, trying to get away from runout damage, but still found the the glue bonded so well, i couldn't remove it without damage to the cocobolo.
Cleanup is not a easy as with hide glue & I'm gonna have to work that out. Also the clamping time is much longer... Otherwise, I'm a convert.
I have heard fish glue is not as reliable on Cedar as HHG. Anyone have experience with that?
Any comments or tips from more experienced folks would be most welcome.
P.S. The HHG I used was not fresh (a few months old, though it looked & smelled fine) so the that portion of the test may not have been totally fair.

Have you tested regular titebond & epoxy to see the difference in those? Those are my two main glues for building a guitar.

Fish glue rules!!!
I use it on everything but the f.b -that I use Epoxy or Poly. for.
I've had great results with Elmers also.

Mike

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Mike Collins

Try to keep in mind that glue test like these are often done with good intentions, but the results don't really offer much useful information. Pretty much anything from Elmer's school glue to wheat paste will give 100% wood failure if you glue it then break it.

To really test strengths and weaknesses is a much much much much more involved process. How do they last after a few hundred cyclical changes between high and low humidity, or temperature, or repeated stress cycles short of the breaking point? Are these results the same on parallel or perpendicular grain joints? Is it prone to creep under long periods of a sustained load? How does it handle repeated flexing - is it brittle and prone to fracture under flex, or if it does have enough give is it prone to creep? How's the sheer strength or impact resistance? Are there any difference between very soft and hard or resinous woods?

These are the points where a glue's strong and weak points become apparent, and there's no way to tell these properties by a simple glue and break test. It becomes pretty quickly apparent that a test to yield any real useful information can become very involved. Lots and lots of samples, humidity and stress control, and consistent setups for different properties, documentation, etc. There is a lot of information already out there on different glues, but they're not all consistent in procedure with each other, and often done by the not-always-objective manufacturer or a lab they hire. I had intentions to a pretty ambitious testing project a few years back, but life and work caught up with me and it became yet another pet project I had to put back on the shelf.

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Eschew obfuscation, espouse elucidation.

I've used the Lee Valley fish glue on cedar with no problems.

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David White, Toronto

"All my favourite singers can't sing."

I agree completely with your points David. I did say it was a "little" test.
The result of note in this test was that the fish glue seemed to penetrate both surfaces of the joint much more deeply that the aliphatic resin glues. The important discovery for me was how difficult it was to chisel the dried glue away from the coco. (I would need to do another test with fresh HHG to make any comment on the difference between the two.)
From what I have read, fish & hot hide glues have similar properties when assessing creep, longevity, brittleness, moisture resistance etc.. Both are widely accepted adhesives in this craft. I am happy to let those with the time & money do that level of testing.
Mark; West system epoxy (105 / 205) is a proven adhesive for my purposes & I have used is with great success on cocobolo, so I didn't include it in my "test".
I don't use Titebond. In my limited experience, I found that Lepage & Elmers are less viscous & do a better job of wetting the surfaces. I also get less slippage with the thinner Lepage & Elmers glues. Might have been a couple of bad batches of Titebond, but once bitten...
Thanks for the comments guys!

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In my experience a LOT has to do with the cocobolo surface - it is easier to glue to a freshly sanded/scraped surface than it is to an older one where the oil has had time to weep toward the surface.

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The member formerly known as erikbojerik....