Titebond II (aliphatic resin) has served me faithfully for about 15 years, as it is very stable throughout temperature changes and highly resistant to moisture, including sweat. It clamps nicely, sands smoothly when dry, and is quite strong.
During seasonal changes however, it sometimes has a tendency to move independent of the wood — perhaps the glue itself is stable, but often the glue line can be felt. A subtle thing but noticeable and not always appropriate on a musical instrument.
Titebond III displays the same properties as Titebond II except I find the dried glue more "rubbery" during sanding, and the glue line more pronounced. For this reason I prefer Titebond II.
Hide glue is on my list to try, but I seldom need to disassemble what I've built.
Lately I've been exploring Gorilla Glue (polyurethane). Different from Gorilla Wood Glue, which I have not yet tested. Foaming action during bonding requires some getting used to but is not an obstacle to success. To avoid over-sensitization I use gloves, eye protection, ventilation and a respirator — the fumes affect my eyes.
I am very pleased with the strength and tightness of the joints. Glue lines are invisible.
During testing I submerged a cutoff walnut & maple scrap from Cupid's neck structure (body glue-up progress below) in water for 36 hours. Note the brown tint to water as color leached from the walnut between start and completion of testing.
Even after 36 hours submersion and subsequent return to room humidity, the glue line was never apparent. Just as impressively, I could not break the joint. Immediately after removing the scrap from water, I bridged it (with the grain) and bounced on it using my full 185 lbs.
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