Official Luthiers Forum!

That makes sense too as the water can't evaporate. I notice the same thing with other water based glues.

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Old growth, shmold growth!

But of course! No stinkin Titebond for us with bridge glues or reglues..... Kidding about the stinkin part, Titebond is great glue, we prefer HHG for bridges.

Chuck there are examples of Egyptian chairs in museums that were glued 1,000 years ago with HHG. Still holding firm!

Regarding the glue shoot outs if you recall the last one that was linked to here on the OLF nearly everyone thought that the testing was flawed and so too the results. Also remember how they rated Franklin bottled hide glue, very high when nearly everyone that I know including myself won't touch that crap for anything beyond perhaps using it to glue in and lubricate frets.

And I agree with you that HHG is "plenty" strong for Lutherie but we will just have to agree to disagree about your assertion that HHG is weaker than Titebond.

Michael I'll try one more time but I remain uncomfortable highjacking the OP's thread to debate the virtues of your testing.

Wood moves.... and it is this dimensional instability that can lead to cyclical fatigue of a glue joint. We have say an ebony bridge glued cross grain in respect to the top on a guitar top. The top is expanding and contracting in one direction and the bridge is doing likewise at roughly 90 degrees. Add the cyclical nature again of the real world for a musical instrument and in time a glue joint can be compromised.

Add in string tension, which DOES impact the bridge, Chuck and is not absorbed by tuners, the neck, etc. and bridges can lift in time or because of a compromised glue joint. Additionally add in abuse, letting the instrument dry out which, by the way increases the dimensional instability at times to the point of cracking.... and bridge come off too.

So when testing the virtues of fish glue on a glue joint gluing two pieces of the same wood together with the same grain direction, not simulating tension, not simulating the cyclical nature of RH changes and the test is useless for Lutherie purposes.

We do a lot of testing here and we are active on other forums publishing our tests. Decent tests are not easy to set-up and there will always be someone who brings up something important that may have been overlooked in the testing. However it is possible to simulate much of what we might be interested in learning so perhaps address the considerations that I have brought up, perhaps too solicit ideas and concerns from others, and then do a comprehensive test that addresses real world conditions for wooden musical instruments and that should get us all some value.

Regarding sizing: Typically with HHG sizing is not done and instead surface prep is favored (for those who care...). We know that freshly scraped surfaces make better glue joints and the reason why or reasons why are a couple in my view. First the surfaces are less damaged from a sharp scrape and second debris is minimized.

Sizing is often done to glean a more homogeneous color on say a guitar top. In Eurpoe sizing is done more often than we tend to do the technique here in the states. I've sized tops before to even out color.

With some glues wetting both srufaces is recommended with epoxy comming to mind. Again in Europe when sizing is done it's often with a very diluded mixture of the glue and also often it's rabbit skin glue. I like rabbits and feed them every day.... But I digress...

So regarding sizing and HHG use I seriously doubt that sizing a HHG joint has any advantages over freshly scraping the joint.

Yup, so that was why I've been clamping my braces so long, no air in that joint either but based on the experience you guys have had with braces it's probably a different situation with such a thin glue line.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Terry I've observed the uncured glue when drilling out the pin holes too and it tends to foul my 3/16th" brad point bits....

I've also had occasion to take a bridge off a day later that had just been glued on with HHG the day before and under the middle of the bridge it's often gooey and gummy and it's pretty clear that the HHG has not fully cured. The first time I observed this it surprised me and also meant that the bridge was at the moment only being held on by the cured glue closer to the perimeter of the bridge. I've always wanted to knock off a bridge a few days later and get a feel for the real cure time deep in a larger glue joint.

One of the things that I learned from this experience was/is not to rush stressing a bridge joint any faster than 24 hours with HHG. It could be that even more time is not a bad idea before stringing her up. If for no other reason than to belay the need to have to clean out my drill bits....

Wood is hygroscopic and absorbs water away from the glue joint allowing the polymers to link up, even if there is no air circulating around it.

The glue will dry EVENTUALLY as water evaporates from the exposed portions of wood and it absorbs more out of the glue joint.

With adequate circulation and as little glue as possible, the process is faster.

That's why I use as little glue as possible and clean up all squeeze-out, if any, to speed things up as much as possible.

For things like wooden binding and purflings however, where there is a pretty good tape coverage, I leave it clamped up (with binding tape) for an hour or so to give the wood time to draw the moisture away from the glue and facilitate polymerization, as the tape covers the outside of the joint.

I also throw a fan on it.

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Old growth, shmold growth!

So squeeze-out is not your friend? It's been my friend for a long time now...

Here's a fun little experiment for folks to do: Take a piece of scrap spruce say the cut-outs from a top. On one end scrape it smooth and on the other end leave it as is. Drop one drop of water on each surface and observe the wet... spot.... Don't want to ruin this for folks so you will have to see what happens on your own but it is interesting and tells a tale too so-to-speak. Very relevant when discussing glue joints, prep, sizing, etc.

The squeezout forms a seal on the edge of the joint. I scrape it off.

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Old growth, shmold growth!